Cisco IOS Configuration Fundamentals Command�Reference, Release�12.2
Basic System Management Commands
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Basic System Management Commands

Table Of Contents

Basic System Management Commands

absolute

alias

buffers

buffers huge size

calendar set

clock calendar-valid

clock read-calendar

clock set

clock summer-time

clock timezone

clock update-calendar

downward-compatible-config

hostname

ip bootp server

ip finger

ip telnet source-interface

ip tftp source-interface

load-interval

ntp access-group

ntp authenticate

ntp authentication-key

ntp broadcast client

ntp broadcast

ntp broadcastdelay

ntp clock-period

ntp disable

ntp master

ntp max-associations

ntp multicast client

ntp multicast

ntp peer

ntp refclock

ntp server

ntp source

ntp trusted-key

ntp update-calendar

periodic

process-max-time

prompt

scheduler allocate

scheduler interval

service decimal-tty

service exec-wait

service finger

service hide-telnet-address

service nagle

service prompt config

service tcp-small-servers

service telnet-zero-idle

service udp-small-servers

show aliases

show buffers

show calendar

show clock

show idb

show ntp associations

show ntp status

show registry

show sntp

sntp broadcast client

sntp server

time-range


Basic System Management Commands


This chapter describes the commands used to perform basic system management tasks, such as naming the router and setting time services. This documentation is specific to Cisco IOS Release 12.2.

For basic system management configuration tasks and examples, refer to the "Performing Basic System Management" chapter in the Release 12.2 Cisco IOS Configuration Fundamentals Configuration Guide.

absolute

To specify an absolute time when a time range is in effect, use the absolute time-range configuration command. To remove the time limitation, use the no form of this command.

absolute [start time date] [end time date]

no absolute

Syntax Description

start time date

(Optional) Absolute time and date that the permit or deny statement of the associated access list starts going into effect. The time is expressed in 24-hour notation, in the form of hours:minutes. For example, 8:00 is 8:00 a.m. and 20:00 is 8:00 p.m. The date is expressed in the format day month year. The minimum start is 00:00 1 January 1993. If no start time and date are specified, the permit or deny statement is in effect immediately.

end time date

(Optional) Absolute time and date that the permit or deny statement of the associated access list is no longer in effect. Same time and date format as described for the start keyword. The end time and date must be after the start time and date. The maximum end time is 23:59 31 December 2035. If no end time and date are specified, the associated permit or deny statement is in effect indefinitely.


Defaults

There is no absolute time when the time range is in effect.

Command Modes

Time-range configuration

Command History

Release
Modification

12.0(1)T

This command was introduced.


Usage Guidelines

Time ranges are used by IP and IPX extended access lists. For more information on using these functions, see the Release 12.2 Cisco IOS IP Configuration Guide and the Release 12.2 Cisco IOS AppleTalk and Novell IPX Configuration Guide. Time ranges are applied to the permit or deny statements found in these access lists.

The absolute command is one way to specify when a time range is in effect. Another way is to specify a periodic length of time with the periodic command. Use either of these commands after the time-range command, which enables time-range configuration mode and specifies a name for the time range. Only one absolute entry is allowed per time-range command.

If a time-range command has both absolute and periodic values specified, then the periodic items are evaluated only after the absolute start time is reached, and are not further evaluated after the absolute end time is reached.


Note All time specifications are interpreted as local time. To ensure that the time range entries take effect at the desired times, the software clock should be synchronized using the Network Time Protocol (NTP), or some other authoritative time source. For more information, refer to the "Performing Basic System Management" chapter of the Release 12.2 Cisco IOS Configuration Fundamentals Configuration Guide.


Examples

The following example configures an access list named northeast, which references a time range named xyz. The access list and time range together permit traffic on Ethernet interface 0 starting at noon on January 1, 2001 and going forever.

time-range xyz
 absolute start 12:00 1 January 2001
!
ip access-list extended northeast
 permit ip any any time-range xyz
!
interface ethernet 0
 ip access-group northeast in

The following example permits UDP traffic until noon on December 31, 2000. After that time, UDP traffic is no longer allowed out Ethernet interface 0.

time-range abc
 absolute end 12:00 31 December 2000
!
ip access-list extended northeast
 permit udp any any time-range abc
!
interface ethernet 0
 ip access-group northeast out

The following example permits UDP traffic out Ethernet interface 0 on weekends only, from 8:00 a.m. on January 1, 1999 to 6:00 p.m. on December 31, 2001:

time-range test
 absolute start 8:00 1 January 1999 end 18:00 31 December 2001 
 periodic weekends 00:00 to 23:59
!
ip access-list extended northeast
 permit udp any any time-range test
!
interface ethernet 0
 ip access-group northeast out

Related Commands

Command
Description

deny

Sets conditions under which a packet does not pass a named access list.

periodic

Specifies a recurring (weekly) start and end time for a time range.

permit

Sets conditions under which a packet passes a named access list.

time-range

Enables time-range configuration mode and names a time range definition.


alias

To create a command alias, use the alias global configuration command. To delete all aliases in a command mode or to delete a specific alias, and to revert to the original command syntax, use the no form of this command.

alias mode command-alias original-command

no alias mode [command-alias]

Syntax Description

mode

Command mode of the original and alias commands.

command-alias

Command alias.

original-command

Original command syntax.


Defaults

A set of six basic EXEC mode aliases are enabled by default. See the "Usage Guidelines" section of this command for a list of default aliases.

Command Modes

Global configuration

Command History

Release
Modification

10.3

This command was introduced.


Usage Guidelines

You can use simple words or abbreviations as command aliases.

Table 44 lists the basic EXEC mode aliases that are enabled by default.

Table 44 Default Command Aliases

Command Alias
Original Command

h

help

lo

logout

p

ping

r

resume

s

show

w

where


The default aliases in Table 44 are predefined. These default aliases can be disabled with the no alias exec command.

Common keyword aliases (which can not be disabled) include running-config (keyword alias for system:running-config) and startup-config (keyword alias for nvram:startup-config). See the description of the copy command for more information about these keyword aliases.

Note that aliases can be configured for keywords instead of entire commands. You can create, for example, an alias for the first part of any command and still enter the additional keywords and arguments as normal.

To determine the value for the mode argument, enter the command mode in which you would issue the original command (and in which you will issue the alias) and enter the ? command. The name of the command mode should appear at the top of the list of commands. For example, the second line in the following sample output shows the name of the command mode as "Interface configuration":

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface e0
Router(config-if)#?
Interface configuration commands:
  access-expression      Build a bridge boolean access expression
  .
  .
  .

To match the name of the command mode to the acceptable mode keyword for the alias command, issue the alias ? command. As shown in the following sample output, the keyword needed to create a command alias for the access-expression command is interface:

Router(config)# alias ?
  accept-dialin          VPDN group accept dialin configuration mode
  accept-dialout         VPDN group accept dialout configuration mode
  address-family         Address Family configuration mode
  call-discriminator     Call Discriminator Configuration
  cascustom              Cas custom configuration mode
  clid-group             CLID group configuration mode
  configure              Global configuration mode
  congestion             Frame Relay congestion configuration mode
  controller             Controller configuration mode
  cptone-set             custom call progress tone configuration mode
  customer-profile       customer profile configuration mode
  dhcp                   DHCP pool configuration mode
  dnis-group             DNIS group configuration mode
  exec                   Exec mode
  flow-cache             Flow aggregation cache config mode
  fr-fr                  FR/FR connection configuration mode
  interface              Interface configuration mode
 .
 .
 .
Router(config)# alias interface express access-expression

For a list of command modes with descriptions and references to related documentation, refer to the "Cisco IOS Command Modes" appendix of the Release 12.2 Cisco IOS Configuration Fundamentals Configuration Guide.

When you use online help, command aliases are indicated by an asterisk (*), and displayed in the following format:

*command-alias=original-command

For example, the lo command alias is shown here along with other EXEC mode commands that start with "lo":

Router#lo?
*lo=logout  lock  login  logout 

When you use online help, aliases that contain multiple keyword elements separated by spaces are displayed in quotes, as shown here:

Router(config)#alias exec device-mail telnet device.cisco.com 25
Router(config)#end
Router#device-mail?
*device-mail="telnet device.cisco.com 25" 

To list only commands and omit aliases, begin your input line with a space. In the following example, the alias td is not shown, because there is a space before the t? command line.

Router(config)#alias exec td telnet device
Router(config)#end
Router# t?
telnet  terminal  test  tn3270  trace

To circumvent command aliases, use a space before entering the command. In the following example, the command alias express is not recognized because a space is used before the command.

Router(config-if)#exp?
*express=access-expression 
Router(config-if)# express ? 
% Unrecognized command 

As with commands, you can use online help to display the arguments and keywords that can follow a command alias. In the following example, the alias td is created to represent the command telnet device. The /debug and /line switches can be added to telnet device to modify the command:

Router(config)#alias exec td telnet device
Router(config)#end
Router#td ?
      /debug     Enable telnet debugging mode
      /line      Enable telnet line mode
      ...
      whois      Whois port
      <cr>
Router# telnet device

You must enter the complete syntax for the command alias. Partial syntax for aliases is not accepted. In the following example, the parser does not recognize the command t as indicating the alias td:

Router#t
% Ambiguous command: "t"

Examples

In the following example, the alias fixmyrt is configured for the clear iproute 209.165.201.16 EXEC mode command:

Router(config)# alias exec fixmyrt clear ip route 209.165.201.16

In the following example, the alias express is configured for the first part of the access-expression interface configuration command:

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface e0
Router(config-if)#?
Interface configuration commands:
  access-expression       Build a bridge boolean access expression
 .
 .
 .

Router(config-if)#exit
Router(config)#alias ?
  accept-dialin         VPDN group accept dialin configuration mode
  accept-dialout        VPDN group accept dialout configuration mode
  address-family        Address Family configuration mode
  call-discriminator    Call Discriminator Configuration
  cascustom             Cas custom configuration mode
  clid-group            CLID group configuration mode
  configure             Global configuration mode
  congestion            Frame Relay congestion configuration mode
  controller            Controller configuration mode
  cptone-set            custom call progress tone configuration mode
  customer-profile      customer profile configuration mode
  dhcp                  DHCP pool configuration mode
  dnis-group            DNIS group configuration mode
  exec                  Exec mode
  flow-cache            Flow aggregation cache config mode
  fr-fr                 FR/FR connection configuration mode
  interface             Interface configuration mode
 .
 .
 .

Router(config)#alias interface express access-expression
Router(config)#int e0
Router(config-if)#exp?
*express=access-expression  

Router(config-if)#express ?
  input     Filter input packets
  output    Filter output packets

!Note that the true form of the command/keyword alias appears on the screen after issuing
!the express ? command.
Router(config-if)#access-expression ?
  input     Filter input packets
  output    Filter output packets
Router(config-if)#ex?
*express=access-expression  exit  

!Note that in the following line, a space is used before the ex? command
!so the alias is not displayed.
Router(config-if)# ex?
exit

!Note that in the following line, the alias can not be recognized because
!a space is used before the command.
Router(config-if)# express ?
% Unrecognized command

Router(config-if)#end 
Router#show alias interface
Interface configuration mode aliases:
  express             access-expression

Related Commands

Command
Description

show aliases

Displays command aliases.


buffers

To make adjustments to initial buffer pool settings and to the limits at which temporary buffers are created and destroyed, use the buffers global configuration command. To return the buffers to their default size, use the no form of this command.

buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free | min-free | initial} number-of-buffers

no buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free | min-free | initial} number-of-buffers

Syntax Description

small

Buffer size of this public buffer pool is 104 bytes.

middle

Buffer size of this public buffer pool is 600 bytes.

big

Buffer size of this public buffer pool is 1524 bytes.

verybig

Buffer size of this public buffer pool is 4520 bytes.

large

Buffer size of this public buffer pool is 5024 bytes.

huge

Default buffer size of this public buffer pool is 18024 bytes. This value can be configured with the buffers huge size command.

type number

Interface type and interface number of the interface buffer pool. The type value cannot be fddi.

permanent

Number of permanent buffers that the system tries to create and keep. Permanent buffers are normally not trimmed by the system.

max-free

Maximum number of free or unallocated buffers in a buffer pool. A maximum of 20,480 small buffers can be constructed in the pool.

min-free

Minimum number of free or unallocated buffers in a buffer pool.

initial

Number of additional temporary buffers that are to be allocated when the system is reloaded. This keyword can be used to ensure that the system has necessary buffers immediately after reloading in a high-traffic environment.

number-of-buffers

Number of buffers to be allocated.


Defaults

The default number of buffers in a pool is determined by the hardware configuration and can be displayed with the show buffers EXEC command.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Normally you need not adjust these parameters; do so only after consulting with technical support personnel.


Note Improper buffer settings can adversely impact system performance.


You cannot configure FDDI buffers.

Examples

Examples of Public Buffer Pool Tuning

The following example keeps at least 50 small buffers free in the system:

Router(config)# buffers small min-free 50

The following example increases the permanent buffer pool allocation for big buffers to 200:

Router(config)# buffers big permanent 200

Example of Interface Buffer Pool Tuning

A general guideline is to display buffers with the show buffers command, observe which buffer pool is depleted, and increase that one.

The following example increases the permanent Ethernet interface 0 buffer pool on a Cisco 4000 router to 96 when the Ethernet 0 buffer pool is depleted:

Router(config)# buffers ethernet 0 permanent 96

Related Commands

Command
Description

load-interval

Changes the length of time for which data is used to compute load statistics.

show buffers

Displays statistics for the buffer pools on the network server.


buffers huge size

To dynamically resize all huge buffers to the value you specify, use the buffers huge size global configuration command. To restore the default buffer values, use the no form of this command.

buffers huge size number-of-bytes

no buffers huge size number-of-bytes

Syntax Description

number-of-bytes

Huge buffer size (in bytes).


Defaults

18,024 bytes

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command only after consulting with technical support personnel. The buffer size cannot be lowered below the default.


Note Improper buffer settings can adversely impact system performance.


Examples

The following example resizes huge buffers to 20,000 bytes:

Router(config)# buffers huge size 20000

Related Commands

Command
Description

buffers

Adjusts the initial buffer pool settings and the limits at which temporary buffers are created and destroyed.

show buffers

Displays statistics for the buffer pools on the network server.


calendar set

To manually set the hardware clock (calendar), use one of the formats of the calendar set EXEC command.

calendar set hh:mm:ss day month year

calendar set hh:mm:ss month day year

Syntax Description

hh:mm:ss

Current time in hours (using 24-hour notation), minutes, and seconds.

day

Current day (by date) in the month.

month

Current month (by name).

year

Current year (no abbreviation).


Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Some platforms have a hardware clock that is separate from the software clock. In Cisco IOS software syntax, the hardware clock is called the "calendar." The hardware clock is a battery-powered chip that runs continuously, even if the router is powered off or rebooted. After you set the hardware clock, the software clock will be automatically set from the hardware clock when the system is restarted or when the clock read-calendar EXEC command is issued. The time specified in this command is relative to the configured time zone.

Examples

The following example manually sets the hardware clock to 1:32 p.m. on July 23, 1997:

Router# calendar set 13:32:00 23 July 1997

Related Commands

Command
Description

clock read-calendar

Performs a one-time update of the software clock from the hardware clock (calendar).

clock set

Sets the software clock.

clock summer-time

Configures the system time to automatically switch to summer time (daylight saving time).

clock timezone

Sets the time zone for display purposes.

clock update-calendar

Performs a one-time update of the hardware clock from the software clock.


clock calendar-valid

To configure a system as an authoritative time source for a network based on its hardware clock (calendar), use the clock calendar-valid global configuration command. To specify that the hardware clock is not an authoritative time source, use the no form of this command.

clock calendar-valid

no clock calendar-valid

Syntax Description

This command has no arguments or keywords.

Defaults

The router is not configured as a time source.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Some platforms have a hardware clock that is separate from the software clock. The hardware clock runs continuously, even if the router is powered off or rebooted. If no outside time source is available on your network, use this command to make the hardware clock an authoritative time source.

Because the hardware clock is not as accurate as other time sources, you should configure this command only when a more accurate time source (such as NTP) is not available.

Examples

The following example configures a router as the time source for a network based on its hardware clock:

Router(config)# clock calendar-valid

Related Commands

Command
Description

ntp master

Configures the Cisco IOS software as an NTP master clock to which peers synchronize themselves when an external NTP source is not available.

vines time use-system

Sets VINES network time based on the system time.


clock read-calendar

To manually read the hardware clock (calendar) settings into the software clock, use the clock read-calendar EXEC command.

clock read-calendar

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Some platforms have a hardware clock that is separate from the software clock. The hardware clock runs continuously, even if the router is powered off or rebooted. When the router is rebooted, the hardware clock is automatically read into the software clock. However, you may use this command to manually read the hardware clock setting into the software clock. This command is useful if the calendar set command has been used to change the setting of the hardware clock.

Examples

The following example configures the software clock to set its date and time by the hardware clock setting:

Router> clock read-calendar

Related Commands

Command
Description

calendar set

Sets the hardware clock.

clock set

Manually sets the software clock.

clock update-calendar

Performs a one-time update of the hardware clock from the software clock.

ntp update-calendar

Periodically updates the hardware clock from the software clock.


clock set

To manually set the system software clock, use one of the formats of the clock set command in privileged EXEC mode.

clock set hh:mm:ss day month year

clock set hh:mm:ss month day year

Syntax Description

hh:mm:ss

Current time in hours (military format), minutes, and seconds.

day

Current day (by date) in the month.

month

Current month (by name).

year

Current year (no abbreviation).


Command Modes

Privileged EXEC mode

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Generally, if the system is synchronized by a valid outside timing mechanism, such as a Network Time Protocol (NTP) or VINES clock source, or if you have a router with hardware clock, you need not set the software clock. Use this command if no other time sources are available. The time specified in this command is relative to the configured time zone.

Examples

The following example manually sets the software clock to 1:32 p.m. on July 23, 1997:

Router# clock set 13:32:00 23 July 1997

Related Commands

Command
Description

calendar set

Sets the hardware clock.

clock read-calendar

Performs a one-time update of the software clock from the hardware clock (calendar).

clock summer-time

Configures the system to automatically switch to summer time (daylight saving time).

clock timezone

Sets the time zone for display purposes.


clock summer-time

To configure the system to automatically switch to summer time (daylight saving time), use one of the formats of the clock summer-time global configuration command. To configure the Cisco IOS software not to automatically switch to summer time, use the no form of this command.

clock summer-time zone recurring [week day month hh:mm week day month hh:mm [offset]]

clock summer-time zone date date month year hh:mm date month year hh:mm [offset]

clock summer-time zone date month date year hh:mm month date year hh:mm [offset]

no clock summer-time

Syntax Description

zone

Name of the time zone (for example, "PDT" for Pacific Daylight Time) to be displayed when summer time is in effect.

recurring

Indicates that summer time should start and end on the corresponding specified days every year.

date

Indicates that summer time should start on the first specific date listed in the command and end on the second specific date in the command.

week

(Optional) Week of the month (1 to 5 or last).

day

(Optional) Day of the week (Sunday, Monday, and so on).

date

Date of the month (1 to 31).

month

(Optional) Month (January, February, and so on).

year

Year (1993 to 2035).

hh:mm

(Optional) Time (military format) in hours and minutes.

offset

(Optional) Number of minutes to add during summer time (default is 60).


Defaults

Summer time is disabled. If the clock summer-time zone recurring command is specified without parameters, the summer time rules default to United States rules. Default of the offset argument is 60.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command if you want to automatically switch to summer time (for display purposes only). Use the recurring form of the command if the local summer time rules are of this form. Use the date form to specify a start and end date for summer time if you cannot use the recurring form.

In both the date and recurring forms of the command, the first part of the command specifies when summer time begins, and the second part specifies when it ends. All times are relative to the local time zone. The start time is relative to standard time. The end time is relative to summer time. If the starting month is chronologically after the ending month, the system assumes that you are in the southern hemisphere.

Examples

The following example specifies that summer time starts on the first Sunday in April at 2 a.m. and ends on the last Sunday in October at 2 a.m.:

Router(config)# clock summer-time PDT recurring 1 Sunday April 2:00 last Sunday October 
2:00

If you live in a place where summer time does not follow the pattern in the first example, you can specify the exact date and times. In the following example, daylight saving time (summer time) is configured to start on October 12, 1997 at 2 a.m., and end on April 26, 1998 at 2 a.m.:

Router(config)# clock summer-time date 12 October 1997 2:00 26 April 1998 2:00

Related Commands

Command
Description

calendar set

Sets the hardware clock.

clock timezone

Sets the time zone for display purposes.


clock timezone

To set the time zone for display purposes, use the clock timezone global configuration command. To set the time to Coordinated Universal Time (UTC), use the no form of this command.

clock timezone zone hours-offset [minutes-offset]

no clock timezone

Syntax Description

zone

Name of the time zone to be displayed when standard time is in effect.

hours-offset

Hours difference from UTC.

minutes-offset

(Optional) Minutes difference from UTC.


Defaults

UTC

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The system internally keeps time in UTC, so this command is used only for display purposes and when the time is manually set.

Table 45 lists common time zone acronyms used for the zone argument.

Table 45 Common Time Zone Acronyms 

Acronym
Time Zone Name and UTC Offset
Europe
 

GMT

Greenwich Mean Time, as UTC

BST

British Summer Time, as UTC + 1 hour

IST

Irish Summer Time, as UTC + 1 hour

WET

Western Europe Time, as UTC

WEST

Western Europe Summer Time, as UTC + 1 hour

CET

Central Europe Time, as UTC + 1

CEST

Central Europe Summer Time, as UTC + 2

EET

Eastern Europe Time, as UTC + 2

EEST

Eastern Europe Summer Time, as UTC + 3

MSK

Moscow Time, as UTC + 3

MSD

Moscow Summer Time, as UTC + 4

United States and Canada
 

AST

Atlantic Standard Time, as UTC -4 hours

ADT

Atlantic Daylight Time, as UTC -3 hours

ET

Eastern Time, either as EST or EDT, depending on place and time of year

EST

Eastern Standard Time, as UTC -5 hours

EDT

Eastern Daylight Saving Time, as UTC -4 hours

CT

Central Time, either as CST or CDT, depending on place and time of year

CST

Central Standard Time, as UTC -6 hours

CDT

Central Daylight Saving Time, as UTC -5 hours

MT

Mountain Time, either as MST or MDT, depending on place and time of year

MST

Mountain Standard Time, as UTC -7 hours

MDT

Mountain Daylight Saving Time, as UTC -6 hours

PT

Pacific Time, either as PST or PDT, depending on place and time of year

PST

Pacific Standard Time, as UTC -8 hours

PDT

Pacific Daylight Saving Time, as UTC -7 hours

AKST

Alaska Standard Time, as UTC -9 hours

AKDT

Alaska Standard Daylight Saving Time, as UTC
-8 hours

HST

Hawaiian Standard Time, as UTC -10 hours

Australia
 

WST

Western Standard Time, as UTC + 8 hours

CST

Central Standard Time, as UTC + 9.5 hours

EST

Eastern Standard/Summer Time, as UTC + 10 hours (+11 hours during summer time)


Table 46 lists an alternative method for referring to time zones, in which single letters are used to refer to the time zone difference from UTC. Using this method, the letter Z is used to indicate the zero meridian, equivalent to UTC, and the letter J (Juliet) is used to refer to the local time zone. Using this method, the International Date Line is between time zones M and Y.

Table 46 Single-Letter Time Zone Designators 

Letter Designator
Word Designator
Difference from UTC

Y

Yankee

UTC -12 hours

X

Xray

UTC -11 hours

W

Whiskey

UTC -10 hours

V

Victor

UTC -9 hours

U

Uniform

UTC -8 hours

T

Tango

UTC -7 hours

S

Sierra

UTC -6 hours

R

Romeo

UTC -5 hours

Q

Quebec

UTC -4 hours

P

Papa

UTC -3 hours

O

Oscar

UTC -2 hours

N

November

UTC -1 hour

Z

Zulu

Same as UTC

A

Alpha

UTC +1 hour

B

Bravo

UTC +2 hours

C

Charlie

UTC +3 hours

D

Delta

UTC +4 hours

E

Echo

UTC +5 hours

F

Foxtrot

UTC +6 hours

G

Golf

UTC +7 hours

H

Hotel

UTC +8 hours

I

India

UTC +9 hours

K

Kilo

UTC +10 hours

L

Lima

UTC +11 hours

M

Mike

UTC +12 hours


The following example sets the time zone to Pacific Standard Time (PST), which is 8 hours behind UTC:

Router(config)# clock timezone PST -8

The following example sets the time zone to Atlantic Time (AT) for Newfoundland, Canada, which is 3.5 hours behind UTC:

Router(config)# clock timezone AT -3 30

Related Commands

Command
Description

calendar set

Sets the hardware clock.

clock set

Manually set the software clock.

clock summer-time

Configures the system to automatically switch to summer time (daylight saving time).

show clock

Displays the software clock.


clock update-calendar

To perform a one-time update of the hardware clock (calendar) from the software clock, use the clock update-calendar in user or privileged EXEC mode.

clock update-calendar

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Some platforms have a hardware clock (calendar) in addition to a software clock. The hardware clock is battery operated, and runs continuously, even if the router is powered off or rebooted.

If the software clock and hardware clock are not synchronized, and the software clock is more accurate, use this command to update the hardware clock to the correct date and time.

Examples

The following example copies the current date and time from the software clock to the hardware clock:

Router> clock update-calendar

Related Commands

Command
Description

clock read-calendar

Performs a one-time update of the software clock from the hardware clock (calendar).

ntp update-calendar

Periodically updates the hardware clock from the software clock.


downward-compatible-config

To generate a configuration that is compatible with an earlier Cisco IOS release, use the downward-compatible-config global configuration command. To remove this feature, use the no form of this command.

downward-compatible-config version

no downward-compatible-config

Syntax Description

version

Cisco IOS release number, not earlier than Release 10.2.


Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

11.1

This command was introduced.


Usage Guidelines

In Cisco IOS Release 10.3, IP access lists changed format. Use the downward-compatible-config command to regenerate a configuration in a format prior to Release 10.3 if you are going to downgrade from your software version to version 10.2 or 10.3. The earliest version value this command accepts is 10.2.

When this command is configured, the router attempts to generate a configuration that is compatible with the specified version. Note that this command affects only IP access lists.

Under some circumstances, the software might not be able to generate a fully backward-compatible configuration. In such a case, the software issues a warning message.

Examples

The following example generates a configuration file compatible with Cisco IOS Release 10.2 access lists:

Router(config)# downward-compatible-config 10.2

Related Commands

Command
Description

access-list (extended)

Provides extended access lists that allow more detailed access lists.

access-list (standard)

Defines a standard XNS access list.


hostname

To specify or modify the host name for the network server, use the hostname global configuration command.

hostname name

Syntax Description

name

New host name for the network server.


Defaults

The factory-assigned default host name is Router.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The host name is used in prompts and default configuration filenames.

Do not expect case to be preserved. Upper- and lowercase characters look the same to many internet software applications. It may seem appropriate to capitalize a name the same way you might do in English, but conventions dictate that computer names appear all lowercase. For more information, refer to RFC 1178, Choosing a Name for Your Computer.

The name must also follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphens. Names must be 63 characters or fewer. For more information, refer to RFC 1035, Domain Names—Implementation and Specification.

Examples

The following example changes the host name to "sandbox":

Router(config)# hostname sandbox

Related Commands

Command
Description

setup

Enables you to make major enhancements to your configurations, for example, adding a protocol suit, making major addressing scheme changes, or configuring newly installed interfaces.


ip bootp server

To enable the BOOTP service on your routing device, use the ip bootp server global configuration command. To disable BOOTP services, use the no form of the command.

ip bootp server

no ip bootp server

Syntax Description

This command has no arguments or keywords.

Defaults

Enabled

Command Modes

Global configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

By default, the BOOTP service is enabled. When disabled, the no ip bootp server command will appear in the configuration file.

The integrated Dynamic Host Configuration Protocol (DHCP) server was introduced in Cisco IOS Release 12.0(1)T. Because DHCP is based on BOOTP, both of these services share the "well-known" UDP server port of 67 (per RFC 951, RFC 1534, and RFC 2131). If both the BOOTP server and DHCP server are disabled, and a helper address is not configured, "ICMP port unreachable" messages will be sent in response to incoming requests on port 67, and the original incoming packet will be discarded.


Note As with all minor services, the async line BOOTP service should be disabled on your system if you do not have a need for it in your network.

Any network device that has UDP, TCP, BOOTP, DHCP or Finger services should be protected by a firewall or have the services disabled to protect against Denial of Service attacks.


Examples

In the following example, BOOTP and DHCP services are disabled on the router:

Router(config)# no ip bootp server 
Router(config)# no service dhcp 

Related Commands

Command
Description

service dhcp

Enables the integrated Dynamic Host Configuration Protocol (DHCP) server and relay agent.


ip finger

To configure a system to accept Finger protocol requests (defined in RFC 742), use the ip finger global configuration command. To disable this service, use the no form of this command.

ip finger [rfc-compliant]

no ip finger

Syntax Description

rfc-compliant

(Optional) Configures the system to wait for "Return" or "/W" input when processing Finger requests. This keyword should not be used for those systems.


Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

11.3

This command was introduced.

12.1(5), 12.1(5)T

This command was changed from being enabled by default to being disabled by default.


Usage Guidelines

The Finger service allows remote users to view the output equivalent to the show users [wide] command.

When ip finger is configured, the router will respond to a telnet a.b.c.d finger command from a remote host by immediately displaying the output of the show users command and then closing the connection.

When the ip finger rfc-compliant command is configured, the router will wait for input before displaying anything (as required by RFC 1288). The remote user can then enter the Return key to display the output of the show users EXEC command, or enter /W to display the output of the show users wide EXEC command. After this information is displayed, the connection is closed.


Note As with all minor services, the Finger service should be disabled on your system if you do not have a need for it in your network.

Any network device that has UDP, TCP, BOOTP, or Finger services should be protected by a firewall or have the services disabled to protect against Denial of Service attacks.


Because of the potential for hung lines, the rfc-compliant form of this command should not be configured for devices with more than 20 simultaneous users.

Examples

The following example disables the Finger protocol:

Router(config)# no ip finger

ip telnet source-interface

To specify the IP address of an interface as the source address for Telnet connections, use the ip telnet source-interface global configuration command. To reset the source address to the default for each connection, use the no form of this command.

ip telnet source-interface interface

no ip telnet source-interface

Syntax Description

interface

The interface whose address is to be used as the source for Telnet connections.


Defaults

The address of the closest interface to the destination as the source address.

Command Modes

Global configuration

Command History

Release
Modification

11.1

This command was introduced.


Usage Guidelines

Use this command to set the IP address of an interface as the source for all Telnet connections.

If the specified interface is not up, the Cisco IOS software selects the address of the interface closest to the destination as the source address.

Examples

The following example forces the IP address for Ethernet interface 1 as the source address for Telnet connections:

Router(config)# ip telnet source-interface Ethernet1

Related Commands

Command
Description

ip radius source-interface

Forces RADIUS to use the IP address of a specified interface for all outgoing RADIUS packets.


ip tftp source-interface

To specify the IP address of an interface as the source address for TFTP connections, use the ip tftp source-interface global configuration command. To return to the default, use the no form of this command.

ip tftp source-interface interface

no ip tftp source-interface

Syntax Description

interface

The interface whose address is to be used as the source for TFTP connections.


Defaults

The address of the closest interface to the destination as the source address.

Command Modes

Global configuration

Command History

Release
Modification

11.1

This command was introduced.


Usage Guidelines

Use this command to set the IP address of an interface as the source for all TFTP connections.

If the specified interface is not up, the Cisco IOS software selects the address of the interface closest to the destination as the source address.

Examples

In the following example, the IP address assigned to the Loopback0 interface will be used as the source address for TFTP connections:

Router(config)# ip tftp source-interface Loopback0

Related Commands

Command
Description

ip ftp source-interface

Forces outgoing FTP packets to use the IP address of a specified interface as the source address.

ip radius source-interface

Forces outgoing RADIUS packets to use the IP address of a specified interface as the source address.


load-interval

To change the length of time for which data is used to compute load statistics, use the load-interval interface configuration command. To revert to the default setting, use the no form of this command.

load-interval seconds

no load-interval seconds

Syntax Description

seconds

Length of time for which data is used to compute load statistics. A value that is a multiple of 30, from 30 to 600 (30, 60, 90, 120, and so on).


Defaults

300 seconds (5 minutes)

Command Modes

Interface configuration

Command History

Release
Modification

10.3

This command was introduced.


Usage Guidelines

If you want load computations to be more reactive to short bursts of traffic, rather than averaged over 5-minute periods, you can shorten the length of time over which load averages are computed.

If the load interval is set to 30 seconds, new data is used for load calculations over a 30-second period. This data is used to compute load statistics, including input rate in bits and packets per second, output rate in bits and packets per second, load, and reliability.

Load data is gathered every 5 seconds. This data is used for a weighted average calculation in which more-recent load data has more weight in the computation than older load data. If the load interval is set to 30 seconds, the average is computed for the last 30 seconds of load data.

The load-interval command allows you to change the default interval of 5 minutes to a shorter or longer period of time. If you change it to a shorter period of time, the input and output statistics that are displayed when you use the show interface command will be more current, and based on more instantaneous data, rather than reflecting a more average load over a longer period of time.

This command is often used for dial backup purposes, to increase or decrease the likelihood of a backup interface being implemented, but it can be used on any interface.

Examples

In the following example, the default 5-minute average is set to a 30-second average. A burst in traffic that would not trigger a dial backup for an interface configured with the default 5-minute interval might trigger a dial backup for this interface that is set for a shorter, 30-second interval.

Router(config)# interface serial 0
Router(config-if)# load-interval 30

Related Commands

Command
Description

show interfaces

Displays statistics for all configured interfaces.


ntp access-group

To control access to the Network Time Protocol (NTP) services on the system, use the ntp access-group command in global configuration mode. To remove access control to the NTP services, use the no form of this command.

ntp access-group {query-only | serve-only | serve | peer} access-list-number

no ntp

Syntax Description

query-only

Allows only NTP control queries. See RFC 1305 (NTP version 3).

serve-only

Allows only time requests.

serve

Allows time requests and NTP control queries, but does not allow the system to synchronize to the remote system.

peer

Allows time requests and NTP control queries and allows the system to synchronize to the remote system.

access-list-number

Number (from 1 to 99) of a standard IP access list.


Defaults

No access control (full access granted to all systems)

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The access group options are scanned in the following order from least restrictive to most restrictive:

1. peer

2. serve

3. serve-only

4. query-only

Access is granted for the first match that is found. If no access groups are specified, all access is granted to all sources. If any access groups are specified, only the specified access is granted. This facility provides minimal security for the time services of the system. However, it can be circumvented by a determined programmer. If tighter security is desired, use the NTP authentication facility.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp access-group command and you now want to remove not only the access group, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure a system to allow itself to be synchronized by a peer from access list 99. However, the system restricts access to allow only time requests from access list 42.

Router(config)# ntp access-group peer 99
Router(config)# ntp access-group serve-only 42

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

access-list

Configures the access list mechanism for filtering frames by protocol type or vendor code.


ntp authenticate

To enable Network Time Protocol (NTP) authentication, use the ntp authenticate command in global configuration mode. To disable the function, use the no form of this command.

ntp authenticate

no ntp

Syntax Description

This command has no arguments or keywords.

Defaults

No authentication

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command if you want authentication. If this command is specified, the system will not synchronize to a system unless it carries one of the authentication keys specified in the ntp trusted-key global configuration command.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp authenticate command and you now want to disable not only the authentication, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure the system to synchronize only to systems that provide authentication key 42 in their NTP packets:

Router(config)# ntp authenticate
Router(config)# ntp authentication-key 42 md5 aNiceKey
Router(config)# ntp trusted-key 42

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp authentication-key

Defines an authentication key for NTP.

ntp trusted-key

Authenticates the identity of a system to which NTP will synchronize.


ntp authentication-key

To define an authentication key for Network Time Protocol (NTP), use the ntp authentication-key command in global configuration mode. To remove the authentication key for NTP, use the no form of this command.

ntp authentication-key number md5 value

no ntp

Syntax Description

number

Key number (from 1 to 4294967295).

md5

Authentication key. Message authentication support is provided using the message digest algorithm 5 (MD5) algorithm. The key type md5 is currently the only key type supported.

value

Key value (an arbitrary string of up to eight characters).


Defaults

No authentication key is defined for NTP.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command to define authentication keys for use with other NTP commands in order to provide a higher degree of security.


Note When this command is written to NVRAM, the key is encrypted so that it is not displayed when the configuration is viewed.


When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp authentication-key command and you now want to remove not only the authentication key, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure the system to synchronize only to systems providing authentication key 42 in their NTP packets:

Router(config)# ntp authenticate
Router(config)# ntp authentication-key 42 md5 aNiceKey
Router(config)# ntp trusted-key 42

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp authenticate

Enables NTP authentication.

ntp peer

Configures the software clock to synchronize a peer or to be synchronized by a peer.

ntp server

Allows the software clock to be synchronized by a time server.

ntp trusted-key

Authenticates the identity of a system to which NTP will synchronize.


ntp broadcast client

To configure the system to receive Network Time Protocol (NTP) broadcast packets on a specified interface, use the ntp broadcast client command in interface configuration mode. To disable this capability, use the no form of this command.

ntp broadcast client

no ntp

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Interface configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command to allow the system to listen to broadcast packets on an interface-by-interface basis.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp broadcast client command and you now want to remove not only the broadcast client capability, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

In the following example, the system is configured to receive (listen to) NTP broadcasts on Ethernet interface 1:

Router(config)# interface ethernet 1
Router(config-if)# ntp broadcast client

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp broadcast

Configures the specified interface to send NTP broadcast packets.

ntp broadcastdelay

Sets the estimated round-trip delay between the system and an NTP broadcast server.


ntp broadcast

To configure the system to send Network Time Protocol (NTP) broadcast packets on a specified interface, use the ntp broadcast command in interface configuration mode. To disable this capability, use the no form of this command.

ntp broadcast [version number]

no ntp

Syntax Description

version

(Optional) Indicates that a version is specified.

number

(Optional) Number from 1 to 3 indicating the NTP version.


Defaults

Disabled

Command Modes

Interface configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp broadcast command and you now want to remove not only the broadcast capability, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configures Ethernet interface 0 to send NTP version 2 broadcasts:

Router(config)# interface ethernet 0
Router(config-if)# ntp broadcast version 2

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp broadcast client

Allows the system to receive NTP broadcast packets on an interface.

ntp broadcastdelay

Sets the estimated round-trip delay between the Cisco IOS software and an NTP broadcast server.


ntp broadcastdelay

To set the estimated round-trip delay between the Cisco IOS software and a Network Time Protocol (NTP) broadcast server, use the ntp broadcastdelay command in global configuration mode. To revert to the default value, use the no form of this command.

ntp broadcastdelay microseconds

no ntp

Syntax Description

microseconds

Estimated round-trip time (in microseconds) for NTP broadcasts. The range is from 1 to 999999.


Defaults

3000 microseconds

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command when the router is configured as a broadcast client and the round-trip delay on the network is other than 3000 microseconds.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp broadcastdelay command and you now want to remove not only the delay setting, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to set the estimated round-trip delay between a router and the broadcast client to 5000 microseconds:

Router(config)# ntp broadcastdelay 5000

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp broadcast

Configures the specified interface to send NTP broadcast packets.

ntp broadcast client

Configures the specified interface to receive NTP broadcast packets.


ntp clock-period


Caution Do not enter this command; it is documented for informational purposes only. The system automatically generates this command as Network Time Protocol (NTP) determines the clock error and compensates.

As NTP compensates for the error in the software clock, it keeps track of the correction factor for this error. The system automatically saves this value into the system configuration when the ntp clock-period command is issued in global configuration mode. To revert to the default, use the no form of this command.

ntp clock-period value

no ntp

Syntax Description

value

Amount of time to add to the software clock for each clock hardware tick (this value is multiplied by 2-32).


Defaults

17179869 2-32 seconds (4 milliseconds)

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Do not manually set a value for the NTP clock-period.

If a copy running-config startup-config command is entered to save the configuration to NVRAM, the ntp clock-period command will automatically be added to the startup configuration. We recommend saving the running configuration to the startup configuration after NTP has been running for a week or so specifically for the purpose of capturing the current setting for the clock-period; performing this task will help NTP synchronize more quickly if the system is restarted.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you want to remove not only the clock period, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows a typical difference between the values of the NTP clock-period setting in the running configuration and in the startup configuration:

Router# show startup-config | include clock-period

ntp clock-period 17180239

Router# show running-config | include clock-period

ntp clock-period 17180255

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

ntp disable

To prevent an interface from receiving Network Time Protocol (NTP) packets, use the ntp disable command in interface configuration mode. To enable receipt of NTP packets on an interface, use the no form of this command.

ntp disable

no ntp

Syntax Description

This command has no arguments or keywords.

Defaults

Enabled

Command Modes

Interface configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

This command provides a simple method of access control.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp disable command and you now want to remove not only this restriction, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to prevent Ethernet interface 0 from receiving NTP packets:

Router(config)# interface ethernet 0
Router(config-if)# ntp disable

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

ntp master

To configure the Cisco IOS software as a Network Time Protocol (NTP) master clock to which peers synchronize themselves when an external NTP source is not available, use the ntp master command in global configuration mode. To disable the master clock function, use the no form of this command.

ntp master [stratum]

no ntp


Caution Use this command with caution. It is very easy to override valid time sources using this command, especially if a low stratum number is configured. Configuring multiple devices in the same network with the ntp master command can cause instability in keeping time if the devices do not agree on the time.

Syntax Description

stratum

(Optional) Number from 1 to 15. Indicates the NTP stratum number that the system will claim.


Defaults

By default, the master clock function is disabled. When enabled, the default stratum is 8.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Because the Cisco implementation of NTP does not support directly attached radio or atomic clocks, the router is normally synchronized, directly or indirectly, to an external system that has such a clock. In a network without Internet connectivity, such a time source may not be available. The ntp master command is used in such cases.

If the system has ntp master configured, and it cannot reach any clock with a lower stratum number, the system will claim to be synchronized at the configured stratum number, and other systems will be willing to synchronize to it via NTP.


Note The software clock must have been set from some source, including manually, before the ntp master command will have any effect. This protects against distributing erroneous time after the system is restarted.


When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp master command and you now want to remove not only the master clock function, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure a router as an NTP master clock to which peers may synchronize:

Router(config)# ntp master 10

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

clock calendar-valid

Configures the system hardware clock an authoritative time source for the network.


ntp max-associations

To configure the maximum number of Network Time Protocol (NTP) peers and clients for the routing device, use the ntp max-associations command in global configuration mode. To return the maximum associations value to the default, use the no form of this command.

ntp max-associations number

no ntp

Syntax Description

number

Specifies the number of NTP associations. The range is 0 to 4294967295. The default is 100.


Defaults

100 maximum associations.

Command Modes

Global configuration

Command History

Release
Modification

12.0

This command was introduced.


Usage Guidelines

The router can be configured to define the maximum number of NTP peer and client associations that the router will serve. The ntp max-associations command is used to set this limit.

This command is useful for ensuring that that the router is not overwhelmed by huge numbers of NTP synchronization requests or, for an NTP master server, to allow large numbers of devices to sync to the router.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp max-associations command and you now want to remove not only that maximum value, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

In the following example, the router is configured to act as an NTP server to 200 clients:

Router(config)# ntp max-associations 200 

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

show ntp associations

Shows all current NTP associations for the device.


ntp multicast client

To configure the system to receive Network Time Protocol (NTP) multicast packets on a specified interface, use the ntp multicast client interface configuration command. To disable this capability, use the no form of this command.

ntp multicast client [ip-address]

no ntp

Syntax Description

ip-address

(Optional) IP address of the multicast group. Default address is 224.0.1.1.


Defaults

Disabled

Command Modes

Interface configuration

Command History

Release
Modification

12.1

This command was introduced.


Usage Guidelines

Use this command to allow the system to listen to multicast packets on an interface-by-interface basis.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp multicast client command and you now want to remove not only the multicast client capability, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

In the following example, the system is configured to receive (listen to) NTP multicast packets on Ethernet interface 1:

Router(config)# interface ethernet 1
Router(config-if)# ntp multicast client

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp multicast

Configures the specified interface to send NTP multicast packets.


ntp multicast

To configure a system to send Network Time Protocol (NTP) multicast packets on a specified interface, use the ntp multicast interface configuration command. To disable this capability, use the no form of this command.

ntp multicast [ip-address] [key key-id] [ttl value] [version number]

no ntp

Syntax Description

ip-address

(Optional) IP address of the multicast group. Default address is 224.0.1.1.

key

(Optional) Defines a multicast authentication key.

key-id

(Optional) Authentication key number in the range from 1 to 4294967295.

ttl

(Optional) Defines the time-to-live (TTL) value of a multicast NTP packet.

value

(Optional) TTL value in the range from 1 to 255. Default TTL value is 16.

version

(Optional) Defines the NTP version number.

number

(Optional) NTP version number in the range from 1 to 3. Default version number is 3.


Defaults

Disabled

Command Modes

Interface configuration

Command History

Release
Modification

12.1

This command was introduced.


Usage Guidelines

The TTL value is used to limit the scope of an audience for multicast routing.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp multicast command and you now want to remove not only the multicast capability, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure Ethernet interface 0 to send NTP version 2 broadcasts:

Router(config)# interface ethernet 0
Router(config-if)# ntp multicast version 2

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp authentication-key

Defines an authentication key for NTP.

ntp multicast client

Allows the system to receive NTP multicast packets on an interface.


ntp peer

To configure the software clock to synchronize a peer or to be synchronized by a peer, use the ntp peer command in global configuration mode. To disable this capability, use the no form of this command.

ntp peer ip-address [normal-sync] [version number] [key key-id] [source interface] [prefer]

no ntp

Syntax Description

ip-address

IP address of the peer providing, or being provided, the clock synchronization.

normal-sync

(Optional) Disables the rapid synchronization at startup.

version

(Optional) Defines the Network Time Protocol (NTP) version number.

number

(Optional) NTP version number (1 to 3).

key

(Optional) Defines the authentication key.

keyid

(Optional) Authentication key to use when sending packets to this peer.

source

(Optional) Names the interface.

interface

(Optional) Name of the interface from which to pick the IP source address.

prefer

(Optional) Makes this peer the preferred peer that provides synchronization.


Command Default

No peers are configured.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.

12.3(14)T

The normal-sync keyword was added.


Usage Guidelines

When a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.

Use this command to allow a device to synchronize with a peer, or vice versa. Using the prefer keyword reduces switching between peers.


Tip If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version 2 (NTPv2).


When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp peer command and you now want to remove not only the peer, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure a router to allow its software clock to be synchronized with the clock of the peer (or vice versa) at IP address 192.168.22.33 using NTP version 2. The source IP address is the address of Ethernet 0.

Router(config)# ntp peer 192.168.22.33 version 2 source ethernet 0

The following example shows how to disable rapid synchronization at startup:

Router(config)# ntp peer 192.168.22.33 normal-sync

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp authentication-key

Defines an authentication key for NTP.

ntp server

Allows the software clock to be synchronized by a time server.

ntp source

Uses a particular source address in NTP packets.


ntp refclock

To configure an external clock source for use with Network Time Protocol (NTP) services, use the ntp refclock command in line configuration mode. To disable support of the external time source, use the no form of this command.

ntp refclock {trimble | telecom-solutions} pps {cts | ri | none} [inverted] [pps-offset number] [stratum number] [timestamp-offset number]

no ntp

Syntax Description

trimble

Enables the reference clock driver for the Trimble Palisade NTP Synchronization Kit (Cisco 7200 series routers only).

telecom-solutions

Enables the reference clock driver for a Telecom Solutions GPS device.

pps

Pulse per second (PPS) signal line. Indicate PPS pulse reference clock support. Choices are cts, ri, or none.

cts

Pulse per second on CTS.

ri

Pulse per second on RI.

none

No PPS signal available.

inverted

(Optional) PPS signal is inverted.

pps-offset number

(Optional) Offset of PPS pulse. The number is the offset (in milliseconds).

stratum number

(Optional) Number from 0 to 14. Indicates the NTP stratum number that the system will claim.

timestamp-offset number

(Optional) Offset of time stamp. The number is the offset (in milliseconds).


Defaults

This command is disabled by default.

Command Modes

Line configuration

Command History

Release
Modification

12.1

The trimble keyword was added to provide driver activation for a Trimble GPS time source on the Cisco 7200 series router.


Usage Guidelines

To configure a PPS signal as the source for NTP synchronization, use the following form of the ntp refclock command:

ntp refclock pps {cts | ri} [inverted] [pps-offset number] [stratum number] [timestamp-offset number]

To configure a Trimble Palisade NTP Synchronization Kit as the GPS clock source connected to the auxiliary port of a Cisco 7200 router, use the following form of the ntp refclock command:

ntp refclock trimble pps none [stratum number]

To configure a Telecom Solutions product as the GPS clock source, use the ntp refclock telecom-solutions form of the command:

ntp refclock telecom-solutions pps cts [stratum number]

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp refclock command and you now want to remove not only the external clock source, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows configuration of a Trimble Palisade GPS time source on a Cisco 7200 router:

Router(config)# ntp master
Router(config)# ntp update-calendar
Router(config)# line aux 0
Router(config-line)# ntp refclock trimble pps none

The following example shows configuration of a Telecom Solutions GPS time source on a Catalyst switch platform:

Router(config)# ntp master
Router(config)# ntp update-calendar
Router(config)# line aux 0
Router(config-line)# ntp refclock telecom-solutions pps cts stratum 1

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

show ntp associations

Displays the status of NTP associations configured for your system.


ntp server

To allow the software clock to be synchronized by a Network Time Protocol (NTP) time server, use the ntp server command in global configuration mode. To disable this capability, use the no form of this command.

ntp server ip-address | hostname [version number] [key key-id] [source interface] [prefer]

no ntp

Syntax Description

ip-address

IP address of the time server providing the clock synchronization.

hostname

Name of the time server providing the clock synchronization.

version

(Optional) Defines the NTP version number.

number

(Optional) NTP version number (1 to 3).

key

(Optional) Defines the authentication key.

key-id

(Optional) Authentication key to use when sending packets to this peer.

source

(Optional) Identifies the interface from which to pick the IP source address.

interface

(Optional) Name of the interface from which to pick the IP source address.

prefer

(Optional) Specifies that the server referenced in this command is preferred over other configured NTP servers.


Defaults

No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command if you want to allow the system to synchronize with the specified server. The server will not synchronize to this machine.

When you use the hostname option, the router does a domain name server (DNS) lookup on that name, and stores the IP address in the configuration. For example, if you enter the command ntp server host1 and then check the running configuration, the output shows "ntp server 172.16.0.4," assuming that the router is correctly configured as a DNS client.

Use the prefer keyword if you use this command multiple times, and you want to set a preferred server. Using the prefer keyword reduces switching between servers.

If you are using the default version of 3 and NTP synchronization does not occur, try NTP version 2. Some NTP servers on the Internet run version 2.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp server command and you now want to remove not only the server synchronization capability, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure a router to allow its software clock to be synchronized with the clock by the device at IP address 172.16.22.44 using NTP version 2:

Router(config)# ntp server 172.16.22.44 version 2

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp authentication-key

Defines an authentication key for NTP.

ntp peer

Configures the software clock to synchronize a peer or to be synchronized by a peer.

ntp source

Uses a particular source address in NTP packets.


ntp source

To use a particular source address in Network Time Protocol (NTP) packets, use the ntp source command in global configuration mode. To remove the specified source address, use the no form of this command.

ntp source type number

no ntp

Syntax Description

type

Type of interface.

number

Number of the interface.


Defaults

Source address is determined by the outgoing interface.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Use this command when you want to use a particular source IP address for all NTP packets. The address is taken from the named interface. This command is useful if the address on an interface cannot be used as the destination for reply packets. If the source keyword is present on an ntp server or ntp peer global configuration command, that value overrides the global value set by this command.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp source command and you now want to remove not only the configured source address, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure a router to use the IP address of Ethernet 0 as the source address of all outgoing NTP packets:

Router(config)# ntp source ethernet 0

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp peer

Configures the software clock to synchronize a peer or to be synchronized by a peer.

ntp server

Allows the software clock to be synchronized by a time server.


ntp trusted-key

To authenticate the identity of a system to which Network Time Protocol (NTP) will synchronize, use the ntp trusted-key command in global configuration mode. To disable authentication of the identity of the system, use the no form of this command.

ntp trusted-key key-number

no ntp

Syntax Description

key-number

Key number of authentication key to be trusted.


Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

If authentication is enabled, use this command to define one or more key numbers (corresponding to the keys defined with the ntp authentication-key command) that a peer NTP system must provide in its NTP packets, in order for this system to synchronize to it. This function provides protection against accidentally synchronizing the system to a system that is not trusted, because the other system must know the correct authentication key.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp trusted-key command and you now want to remove not only the authentication, but all NTP functions from the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure the system to synchronize only to systems providing authentication key 42 in its NTP packets:

Router(config)# ntp authenticate
Router(config)# ntp authentication-key 42 md5 aNiceKey
Router(config)# ntp trusted-key 42

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

ntp authenticate

Enables NTP authentication.

ntp authentication-key

Defines an authentication key for NTP.


ntp update-calendar

To periodically update the hardware clock (calendar) from a Network Time Protocol (NTP) time source, use the ntp update-calendar command in global configuration mode. To disable the periodic updates, use the no form of this command.

ntp update-calendar

no ntp

Syntax Description

This command has no arguments or keywords.

Defaults

The hardware clock (calendar) is not updated.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Some platforms have a battery-powered hardware clock, referred to in the command-line interface (CLI) as the "calendar," in addition to the software based system clock. The hardware clock runs continuously, even if the router is powered off or rebooted.

If the software clock is synchronized to an outside time source via NTP, it is a good practice to periodically update the hardware clock with the time learned from NTP. Otherwise, the hardware clock will tend to gradually lose or gain time (drift), and the software clock and hardware clock may become out of synchronization with each other. The ntp update-calendar command will enable the hardware clock to be periodically updated with the time specified by the NTP source. The hardware clock will be updated only if NTP has synchronized to an authoritative time server.

Many lower-end routers (for example, the Cisco 2500 series or the Cisco 2600 series) do not have hardware clocks, so this command is not available on those platforms.

To force a single update of the hardware clock from the software clock, use the clock update-calendar EXEC command.

When you configure NTP, you must include at least one of the available keywords; the NTP service is activated and the keyword takes effect.

In the no form of ntp commands, all the keywords are optional. When you enter the no ntp command followed by one or more of its keywords, only the functions activated by those keywords are removed from the NTP service. The NTP service itself remains active, along with all functions you have not specified in the no ntp command.

To terminate NTP service on a device, you must enter the no ntp command without keywords.

For example, if you previously issued the ntp update-calendar command and you now want to disable not only the periodic updates, but all NTP functions running on the device, use the no ntp command without any keywords. This ensures that all NTP functions are removed and that the NTP service is also terminated.

Examples

The following example shows how to configure the system to periodically update the hardware clock from the NTP time source:

Router(config)# ntp update-calendar

The following example shows how to remove all the configured NTP options and disable the ntp server:

Router(config)# no ntp

Related Commands

Command
Description

clock read-calendar

Performs a one-time update of the software clock from the hardware clock (calendar).

clock update-calendar

Performs a one-time update of the hardware clock (calendar) from the software clock.



periodic

To specify a recurring (weekly) time range for functions that support the time-range feature, use the periodic time-range configuration command. To remove the time limitation, use the no form of this command.

periodic days-of-the-week hh:mm to [days-of-the-week] hh:mm

no periodic days-of-the-week hh:mm to [days-of-the-week] hh:mm

Syntax Description

days-of-the-week

The first occurrence of this argument is the starting day or day of the week that the associated time range is in effect. The second occurrence is the ending day or day of the week the associated statement is in effect.

This argument can be any single day or combinations of days: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. Other possible values are:

daily—Monday through Sunday

weekdays—Monday through Friday

weekend—Saturday and Sunday

If the ending days of the week are the same as the starting days of the week, they can be omitted.

hh:mm

The first occurrence of this argument is the starting hours:minutes that the associated time range is in effect. The second occurrence is the ending hours:minutes the associated statement is in effect.

The hours:minutes are expressed in a 24-hour clock. For example, 8:00 is 8:00 a.m. and 20:00 is 8:00 p.m.

to

Entry of the to keyword is required to complete the range "from start-time to end-time."


Defaults

No recurring time range is defined.

Command Modes

Time-range configuration

Command History

Release
Modification

12.0(1)T

This command was introduced.


Usage Guidelines

For Cisco IOS Release 12.2, IP and Internetwork Packet Exchange (IPX) extended access lists are the only functions that can use time ranges. For further information on using these functions, refer to the Release 12.2 Cisco IOS IP Configuration Guide and the Release 12.2 Cisco IOS AppleTalk and Novell IPX Configuration Guide.

The periodic command is one way to specify when a time range is in effect. Another way is to specify an absolute time period with the absolute command. Use either of these commands after the time-range global configuration command, which specifies the name of the time range. Multiple periodic entries are allowed per time-range command.

If the end days-of-the-week value is the same as the start value, they can be omitted.

If a time-range command has both absolute and periodic values specified, then the periodic items are evaluated only after the absolute start time is reached, and are not further evaluated after the absolute end time is reached.


Note All time specifications are taken as local time. To ensure that the time range entries take effect at the desired times, you should synchronize the system software clock using Network Time Protocol (NTP).


Table 47 lists some typical settings for your convenience:

Table 47 Typical Examples of periodic Command Syntax

If you want:
Configure this:

Monday through Friday, 8:00 a.m. to 6:00 p.m. only

periodic weekday 8:00 to 18:00

Every day of the week, from 8:00 a.m. to 6:00 p.m. only

periodic daily 8:00 to 18:00

Every minute from Monday 8:00 a.m. to Friday 8:00 p.m.

periodic monday 8:00 to friday 20:00

All weekend, from Saturday morning through Sunday night

periodic weekend 00:00 to 23:59

Saturdays and Sundays, from noon to midnight

periodic weekend 12:00 to 23:59


Examples

The following example denies HTTP traffic on Monday through Friday from 8:00 a.m. to 6:00 p.m.:

time-range no-http
 periodic weekdays 8:00 to 18:00
!
ip access-list extended strict
 deny tcp any any eq http time-range no-http
!
interface ethernet 0
 ip access-group strict in

The following example permits Telnet traffic on Mondays, Tuesdays, and Fridays from 9:00 a.m. to
5:00 p.m.:

time-range testing
 periodic Monday Tuesday Friday 9:00 to 17:00
!
ip access-list extended legal
 permit tcp any any eq telnet time-range testing
!
interface ethernet 0
 ip access-group legal in

Related Commands

Command
Description

absolute

Specifies an absolute start and end time for a time range.

access-list (extended)

Defines an extended IP access list.

deny (IP)

Sets conditions under which a packet does not pass a named IP access list.

permit (IP)

Sets conditions under which a packet passes a named IP access list.

time-range

Enables time-range configuration mode and names a time range definition.


process-max-time

To configure the amount of time after which a process should voluntarily yield to another process, use the process-max-time command in global configuration mode. To reset this value to the system default, use the no form of this command.

process-max-time milliseconds

no process-max-time [milliseconds]

Syntax Description

milliseconds

Maximum duration (in milliseconds) that a process can run before suspension. The range is from 20-200 milliseconds.


Defaults

Default maximum process time is 200 milliseconds.

Command Modes

Global configuration

Command History

Release
Modification

12.1

This command was introduced.


Usage Guidelines

Lowering the maximum time a process can run is useful in some circumstances to ensure equitable division of CPU time among different tasks.

Only use this command if recommended to do so by the Cisco Technical Assistance Center (TAC).

Examples

The following example limits the time to 100 milliseconds that a process can run without suspending:

process-max-time 100

prompt

To customize the CLI prompt, use the prompt global configuration command. To revert to the default prompt, use the no form of this command.

prompt string

no prompt [string]

Syntax Description

string

Text that will be diplayed on screen as the CLI prompt, including any desired prompt variables.


Defaults

The default prompt is either Router or the name defined with the hostname global configuration command, followed by an angle bracket (>) for user EXEC mode or a pound sign (#) for privileged EXEC mode.

Command Modes

Global configuration

Command History

Release
Modification

10.3

This command was introduced.


Usage Guidelines

You can include customized variables when specifying the prompt. All prompt variables are preceded by a percent sign (%). Table 48 lists the availble prompt variables.

Table 48 Custom Prompt Variables

Prompt Variable
Interpretation

%h

Host name. This is either Router or the name defined with the hostname global configuration command.

%n

Physical terminal line (tty) number of the EXEC user.

%p

Prompt character itself. It is either an angle bracket (>) for user EXEC mode or a pound sign (#) for privileged EXEC mode.

%s

Space.

%t

Tab.

%%

Percent sign (%)


Issuing the prompt %h command has the same effect as issuing the no prompt command.

Examples

The following example changes the EXEC prompt to include the tty number, followed by the name and a space:

Router(config)# prompt TTY%n@%h%s%p

The following are examples of user and privileged EXEC prompts that result from the previous command:

TTY17@Router1 > enable
TTY17@Router1 #

Related Commands

Command
Description

hostname

Specifies or modifies the host name for the network server.


scheduler allocate

To guarantee CPU time for processes, use the scheduler allocate global configuration command on the Cisco 7200 series and Cisco 7500 series routers. To restore the default, use the no form of this command.

scheduler allocate interrupt-time process-time

no scheduler allocate

Syntax Description

interrupt-time

Integer (in microseconds) that limits the maximum number of microseconds to spend on fast switching within any one network interrupt context. The range is from 400 to 60000 microseconds. The default is 4000 microseconds.

process-time

Integer (in microseconds) that guarantees the minimum number of microseconds to spend at the process level when network interrupts are disabled. The range is from 100 to 4000 microseconds. The default is 200 microseconds.


Defaults

Approximately 5 percent of the CPU is available for process tasks.

Command Modes

Global configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

This command applies to the Cisco 7200 series and Cisco 7500 series routers.


Note Changing settings associated with CPU processes can negatively impact system performance.


Examples

The following example makes 20 percent of the CPU available for process tasks:

Router(config)# scheduler allocate 2000 500

Related Commands

Command
Description

scheduler interval

Controls the maximum amount of time that can elapse without running system processes.


scheduler interval

To control the maximum amount of time that can elapse without running system processes, use the scheduler interval global configuration command. To restore the default, use the no form of this command.

scheduler interval milliseconds

no scheduler interval

Syntax Description

milliseconds

Integer that specifies the interval (in milliseconds). The minimum interval that you can specify is 500 milliseconds; there is no maximum value.


Defaults

High-priority operations are allowed to use as much of the CPU as needed.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The normal operation of the network server allows the switching operations to use as much of the central processor as is required. If the network is running unusually heavy loads that do not allow the processor the time to handle the routing protocols, give priority to the system process scheduler. High-priority operations are allowed to use as much of the CPU as needed.


Note Changing settings associated with CPU processes can negatively impact system performance.


On the Cisco 7200 series and Cisco 7500 series, use the scheduler allocate global configuration command instead of the scheduler interval command.

Examples

The following example changes the low-priority process schedule to an interval of 750 milliseconds:

Router(config)# scheduler interval 750

Related Commands

Command
Description

scheduler allocate

Guarantees CPU time for processes.


service decimal-tty

To specify that line numbers be displayed and interpreted as decimal numbers rather than octal numbers, use the service decimal-tty global configuration command. To display octal numbers, use the no form of this command.

service decimal-tty

no service decimal-tty

Syntax Description

This command has no arguments or keywords.

Defaults

Decimal numbers are displayed.

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Examples

The following example displays decimal rather than octal line numbers:

Router(config)# service decimal-tty

service exec-wait

To delay the startup of the EXEC on noisy lines, use the service exec-wait global configuration command. To disable the delay function, use the no form of this command.

service exec-wait

no service exec-wait

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

This command delays startup of the EXEC until the line has been idle (no traffic seen) for 3 seconds. The default is to enable the line immediately on modem activation.

This command is useful on noisy modem lines or when a modem attached to the line is configured to ignore MNP/V.42 negotiations, and MNP/V.42 modems may be dialing in. In these cases, noise or MNP/V.42 packets may be interpreted as usernames and passwords, causing authentication failure before the user has a chance to type a username or password. The command is not useful on nonmodem lines or lines without some kind of login configured.

Examples

The following example delays the startup of the EXEC:

Router(config)# service exec-wait

service finger

The service finger command has been replaced by the ip finger command. However, the service finger and no service finger commands continue to function to maintain backward compatibility with older versions of Cisco IOS software. Support for this command may be removed in a future release. See the description of the ip finger command in this chapter for more information.

service hide-telnet-address

To hide addresses while trying to establish a Telnet session, use the service hide-telnet-address global configuration command. To remove this service, use the no form of this command.

service hide-telnet-address

no service hide-telnet-address

Syntax Description

This command has no arguments or keywords.

Defaults

Addresses are displayed.

Command Modes

Global configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

When you attempt to connect to a device, the router displays addresses and other messages (for example, "Trying router1 (171.69.1.154, 2008)...)." With the hide feature, the router suppresses the display of the address (for example, "Trying router1 address #1..."). The router continues to display all other messages that would normally be displayed during a connection attempt, such as detailed error messages if the connection was not successful.

The hide feature improves the functionality of the busy-message feature. When you configure only the busy-message command, the normal messages generated during a connection attempt are not displayed; only the busy-message is displayed. When you use the hide and busy features together you can customize the information displayed during Telnet connection attempts. When you configure the service hide-telnet-address command and the busy-message command, the router suppresses the address and displays the message specified with the busy-message command if the connection attempt is not successful.

Examples

The following example hides Telnet addresses:

Router(config)# service hide-telnet-address

Related Commands

Command
Description

busy-message

Creates a "host failed" message that is displayed when a connection fails.


service nagle

To enable the Nagle congestion control algorithm, use the service nagle global configuration command. To to disable the algorithm, use the no form of this command.

service nagle

no service nagle

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

When using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed. On larger networks, many small packets use up bandwidth and contribute to congestion.

The algorithm developed by John Nagle (RFC 896) helps alleviate the small-packet problem in TCP. In general, it works this way: The first character typed after connection establishment is sent in a single packet, but TCP holds any additional characters typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace them out to the network at a rate matching the round-trip time of the given connection. This method is usually effective for all TCP-based traffic. However, do not use the service nagle command if you have XRemote users on X Window system sessions.

Examples

The following example enables the Nagle algorithm:

Router(config)# service nagle

service prompt config

To display the configuration prompt (config), use the service prompt config global configuration command. To remove the configuration prompt, use the no form of this command.

service prompt config

no service prompt config

Syntax Description

This command has no arguments or keywords.

Defaults

The configuration prompts appear in all configuration modes.

Command Modes

Global configuration

Command History

Release
Modification

11.1

This command was introduced.


Examples

In the following example, the no service prompt config command prevents the configuration prompt from being displayed. The prompt is still displayed in EXEC mode. When the service prompt config command is entered, the configuration mode prompt reappears.

Router# configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# no service prompt config
hostname newname
end
newname# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
service prompt config
newname(config)# hostname Router
Router(config)# end
Router#

Related Commands

Command
Description

hostname

Specifies or modifies the host name for the network server.

prompt

Customizes the prompt.


service tcp-small-servers

To access minor TCP/IP services available from hosts on the network, use the service tcp-small-servers command in global configuration mode. To disable these services, use the no form of the command.

service tcp-small-servers

no service tcp-small-servers

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

11.1

This command was introduced.


Usage Guidelines

By default, the TCP servers for Echo, Discard, Chargen, and Daytime services are disabled.

When the minor TCP/IP servers are disabled, access to the Echo, Discard, Chargen, and Daytime ports cause the Cisco IOS software to send a TCP RESET packet to the sender and discard the original incoming packet.

Examples

The following example enables minor TCP/ IP services available from the network:

Router(config)# service tcp-small-servers 

service telnet-zero-idle

To set the TCP window to zero (0) when the Telnet connection is idle, use the service telnet-zero-idle global configuration command. To disable this service, use the no form of this command.

service telnet-zero-idle

no service telnet-zero-idle

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Normally, data sent to noncurrent Telnet connections is accepted and discarded. When the service telnet-zero-idle command is enabled, if a session is suspended (that is, some other connection is made active or the EXEC is sitting in command mode), the TCP window is set to zero. This action prevents the remote host from sending any more data until the connection is resumed. Use this command when it is important that all messages sent by the host be seen by the users and the users are likely to use multiple sessions.

Do not use this command if your host will eventually time out and log out a TCP user whose window is zero.

Examples

The following example sets the TCP window to zero when the Telnet connection is idle:

Router(config)# service telnet-zero-idle

Related Commands

Command
Description

resume

Switches to another open Telnet, rlogin, LAT, or PAD session.


service udp-small-servers

To access minor User Datagram Protocol (UDP) services available from hosts on the network, use the service udp-small-servers global configuration command. To disable these services, use the no form of this command.

service udp-small-servers

no service udp-small-servers

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

By default the UPD servers for Echo, Discard, and Chargen services are disabled.

When the servers are disabled, access to Echo, Discard, and Chargen ports causes the Cisco IOS software to send an "ICMP port unreachable" message to the sender and discard the original incoming packet.

Examples

In the following example minor UDP services are enabled on the router:

Router(config)# service udp-small-servers

show aliases

To display all alias commands, or the alias commands in a specified mode, use the show aliases EXEC command.

show aliases [mode]

Syntax Description

mode

(Optional) Command mode.


Command Modes

EXEC

Command History

Release
Modification

10.3

This command was introduced.


Usage Guidelines

When used without the mode argument, this command will display all aliases currently configured on the system. Use the mode argument to display only the aliases configured for the specified command mode.

To display a list of the command mode keywords available for your system, use the show aliases ? command. For a list of command modes, refer to the "Cisco IOS Command Modes" appendix in the Release 12.2 Cisco IOS Configuration Fundamentals Configuration Guide.

Examples

The following is sample output from the show aliases exec commands. The aliases configured for commands in EXEC mode are displayed.

Router> show aliases exec

Exec mode aliases:
  h                    help
  lo                   logout
  p                    ping
  r                    resume
  s                    show
  w                    where

Related Commands

Command
Description

alias

Creates a command alias.


show buffers

To display statistics for the buffer pools on the network server, use the show buffers EXEC command.

show buffers [address hex-addr |[all | assigned | failures | free | old [dump | header | packet]]
| input-interface interface-type identifier | pool pool-name]

Syntax Description

address

(Optional) Displays buffers at a specified address.

hex-addr

Address (in hexadecimal notation) of the buffer to display.

all

(Optional) Displays all buffers.

assigned

(Optional) Displays the buffers in use.

failures

(Optional) Displays buffer allocation failures.

free

(Optional) Displays the buffers available for use.

old

(Optional) Displays buffers older than one minute.

dump

(Optional) Displays the buffer header and all data in the display.

header

(Optional) Displays the buffer header only in the display.

packet

(Optional) Displays the buffer header and packet data in the display.

input-interface

(Optional) Displays interface pool information. If the specified interface-type argument has its own buffer pool, displays information for that pool.

interface-type

Value of interface-type can be ethernet, fastethernet, loopback, serial, or null.

identifier

Identifier of the interface specified in interface-type argument.

pool

(Optional) Displays buffers in a specified buffer pool.

pool-name

Specifies the name of a buffer pool to use.


Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The peak field in the output of the show buffers command shows the maximum number of buffers created (highest total) and the time when that peak occurred relative to when you issued the show buffers command. Formats include weeks, days, hours, minutes, and seconds. Not all systems report a peak value, which means this field may not display in output.

Examples

The following is sample output from the show buffers command with no arguments, showing all buffer pool information:

Router> show buffers

Buffer elements:
     398 in free list (500 max allowed)
     1266 hits, 0 misses, 0 created
 
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
     50 in free list (20 min, 150 max allowed)
     551 hits, 0 misses, 0 trims, 0 created
Middle buffers, 600 bytes (total 25, permanent 25):
     25 in free list (10 min, 150 max allowed)
     39 hits, 0 misses, 0 trims, 0 created
Big buffers, 1524 bytes (total 50, permanent 50):
     49 in free list (5 min, 150 max allowed)
     27 hits, 0 misses, 0 trims, 0 created
VeryBig buffers, 4520 bytes (total 10, permanent 10):
     10 in free list (0 min, 100 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Large buffers, 5024 bytes (total 0, permanent 0):
     0 in free list (0 min, 10 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Huge buffers, 18024 bytes (total 0, permanent 0):
     0 in free list (0 min, 4 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
          
Interface buffer pools:
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Ethernet1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing0 buffers, 4516 bytes (total 48, permanent 48):
     0 in free list (0 min, 48 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing1 buffers, 4516 bytes (total 32, permanent 32):
     32 in free list (0 min, 48 max allowed)
     16 hits, 0 fallbacks
     0 failures (0 no memory)

The following is sample output from the show buffers command with no arguments, showing onlybuffer pool information for Huge buffers. This output shows a highest total of five Huge buffers created five days and 18 hours before the command was issued.

Router> show buffers

Huge buffers, 18024 bytes (total 5, permanent 0, peak 5 @ 5d18h): 
     4 in free list (3 min, 104 max allowed) 
     0 hits, 1 misses, 101 trims, 106 created 
     0 failures (0 no memory)

The following is sample output from the show buffers command with no arguments, showing only buffer pool information for Huge buffers. This output shows a highest total of 184 Huge buffers created one hour, one minute, and 15 seconds before the command was issued.

Router> show buffers

Huge buffers, 65280 bytes (total 4, permanent 2, peak 184 @ 01:01:15):
     4 in free list (0 min, 4 max allowed)
     32521 hits, 143636 misses, 14668 trims, 14670 created
     143554 failures (0 no memory)

The following is sample output from the show buffers command with an interface type and interface number:

Router> show buffers Ethernet 0

Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks

16 max cache size, 16 in cache

Table 49 describes significant fields shown in the display.

Table 49 show buffers Field Descriptions 

Field
Description

Buffer elements

Small structures used as placeholders for buffers in internal operating system queues. Used when a buffer may need to be on more than one queue.

free list

Total number of the currently unallocated buffer elements.

max allowed

Maximum number of buffers that are available for allocation.

hits

Count of successful attempts to allocate a buffer when needed.

misses

Count of buffer allocation attempts that resulted in growing the buffer pool to allocate a buffer.

created

Count of new buffers created to satisfy buffer allocation attempts when the available buffers in the pool have already been allocated.

Public buffer pools:

 Small buffers

Buffers that are 104 bytes long.

  Middle buffers

Buffers that are 600 bytes long.

 Big buffers

Buffers that are 1524 bytes long.

 VeryBig buffers

Buffers that are 4520 bytes long.

 Large buffers

Buffers that are 5024 bytes long.

 Huge buffers

Buffers that are 18024 bytes long.

  total

Total number of this type of buffer.

  permanent

Number of these buffers that are permanent.

  peak

Maximum number of buffers created (highest total) and the time when that peak occurred. Formats include weeks, days, hours, minutes, and seconds. Not all systems report a peak value, which means this field may not display in output.

  free list

Number of available or unallocated buffers in that pool.

  min

Minimum number of free or unallocated buffers in the buffer pool.

  max allowed

Maximum number of free or unallocated buffers in the buffer pool.

  hits

Count of successful attempts to allocate a buffer when needed.

  misses

Count of buffer allocation attempts that resulted in growing the buffer pool in order to allocate a buffer.

  trims

Count of buffers released to the system because they were not being used. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static.

  created

Count of new buffers created in response to misses. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static.

Interface buffer pools:

  total

Total number of this type of buffer.

  permanent

Number of these buffers that are permanent.

  free list

Number of available or unallocated buffers in that pool.

  min

Minimum number of free or unallocated buffers in the buffer pool.

  max allowed

Maximum number of free or unallocated buffers in the buffer pool.

  hits

Count of successful attempts to allocate a buffer when needed.

  fallbacks

Count of buffer allocation attempts that resulted in falling back to the public buffer pool that is the smallest pool at least as big as the interface buffer pool.

  max cache size

Maximum number of buffers from the pool of that interface that can be in the buffer pool cache of that interface. Each interface buffer pool has its own cache. These are not additional to the permanent buffers; they come from the buffer pools of the interface. Some interfaces place all of their buffers from the interface pool into the cache. In this case, it is normal for the free list to display 0.

failures

Total number of times a buffer creation failed. The failure may have occurred because of a number of different reasons, such as low processor memory, low IOMEM, or no buffers in the pool when called from interrupt context.

no memory

Number of times there has been low memory during buffer creation. Low or no memory during buffer creation may not necessarily mean that buffer creation failed; memory can be obtained from an alternate resource such as a fallback pool.


show calendar

To display the current time and date setting for the hardware clock, use the show calendar EXEC command:

show calendar

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

Some platforms have a hardware clock (calendar) which is separate from the software clock. The hardware clock is battery operated, and runs continuously, even if the router is powered off or rebooted.

You can compare the time and date shown with this command with the time and date listed via the show clock EXEC command to verify that the hardware clock and software clock are synchronized with each other. The time displayed is relative to the configured time zone.

Examples

In the following sample display, the hardware clock indicates the time stamp of 12:13:44 p.m. on Friday, July 19, 1996:

Router> show calendar

12:13:44 PST Fri Jul 19 1996

Related Commands

Command
Description

show clock

Displays the time and date from the system software clock.


show clock

To display the time and date from the system software clock, use the show clock EXEC command.

show clock [detail]

Syntax Description

detail

(Optional) Indicates the clock source (NTP, VINES, hardware clock, and so on) and the current summer-time setting (if any).


Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The software clock keeps an "authoritative" flag that indicates whether the time is authoritative (believed to be accurate). If the software clock has been set by a timing source (for example, via NTP), the flag is set. If the time is not authoritative, it will be used only for display purposes. Until the clock is authoritative and the "authoritative" flag is set, the flag prevents peers from synchronizing to the software clock.

The symbol that precedes the show clock display indicates the following:

Symbol
Description

*

Time is not authoritative.

(blank)

Time is authoritative.

.

Time is authoritative, but NTP is not synchronized.



Note In general, NTP synchronization takes approximately 15 to 20 minutes.


Examples

The following sample output shows that the current clock is authoritative and that the time source is NTP:

Router> show clock detail

15:29:03.158 PST Mon Mar 3 1999
Time source is NTP

The following example shows the current clock is authoritative, but NTP is not yet synchronized:

Router> show clock

.16:42:35.597 UTC Wed Nov 1 1999

Related Commands

Command
Description

clock set

Manually sets the software clock.

show calendar

Displays the current time and date setting of the system hardware clock.


show idb

To display information about the status of interface descriptor blocks (IDBs), use the show idb command in privileged EXEC mode.

show idb

Syntax Description

This command has nor arguments or keywords.

Defaults

No default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.1

This command was introduced.

12.2(15)T

The output of this command was changed to show additional information.


Examples

The following is sample output from the show idb command:

Router# show idb

Maximum number of Software IDBs 8192.  In use 17.

                       HWIDBs     SWIDBs
Active                      5         14
Inactive                   10          3
Total IDBs                 15         17
Size each (bytes)        5784       2576
Total bytes             86760      43792

HWIDB#1   1   2   GigabitEthernet0/0 0 5, HW IFINDEX, Ether)
HWIDB#2   2   3   GigabitEthernet9/0 0 5, HW IFINDEX, Ether)
HWIDB#3   3   4   GigabitEthernet9/1 6 5, HW IFINDEX, Ether)
HWIDB#4   4   5   GigabitEthernet9/2 6 5, HW IFINDEX, Ether)
HWIDB#5   13  1   Ethernet0 4 5, HW IFINDEX, Ether)

Table 50 describes the significant fields shown in the display.

Table 50 show idb Field Descriptions

Field
Description

In use

Total number of software IDBs (SWIDBs) that have been allocated. This number never decreases. SWIDBs are never deallocated.

Active

Total number of hardware IDBs (HWIDBs) and SWIDBs that are allocated and in use.

Inactive

Total number of HWIDBs and SWIDBs that are allocated but not in use.

Total

Total number of HWIDBs and SWIDBs that are allocated.


show ntp associations

To show the status of Network Time Protocol (NTP) associations, use the show ntp associations EXEC command.

show ntp associations [detail]

Syntax Description

detail

(Optional) Displays detailed information about each NTP association.


Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Examples

Detailed descriptions of the information displayed by this command can be found in the NTP specification (RFC 1305).

The following is sample output from the show ntp associations command:

Router> show ntp associations

     address         ref clock     st  when  poll  reach  delay  offset    disp
 ~172.31.32.2      172.31.32.1       5    29  1024  377     4.2   -8.59     1.6
+~192.168.13.33    192.168.1.111     3    69   128  377     4.1    3.48     2.3
*~192.168.13.57    192.168.1.111     3    32   128  377     7.9   11.18     3.6
* master (synced), # master (unsynced), + selected, - candidate, ~ configured

Table 51 describes the significant fields shown in the display.

Table 51 show ntp associations Field Descriptions 

Field
Description

(leading characters in display lines)

The first characters in a display line can be one or more of the following characters:

* —Synchronized to this peer

# —Almost synchronized to this peer

+ —Peer selected for possible synchronization

- —Peer is a candidate for selection

~ —Peer is statically configured

address

Address of peer.

ref clock

Address of reference clock of peer.

st

Stratum of peer.

when

Time since last NTP packet was received from peer.

poll

Polling interval (in seconds).

reach

Peer reachability (bit string, in octal).

delay

Round-trip delay to peer (in milliseconds).

offset

Relative time of peer clock to local clock (in milliseconds).

disp

Dispersion


The following is sample output of the show ntp associations detail command:

Router> show ntp associations detail

172.31.32.2 configured, insane, invalid, stratum 5
ref ID 172.31.32.1, time AFE252C1.6DBDDFF2 (00:12:01.428 PDT Mon Jul 5 1993)
our mode active, peer mode active, our poll intvl 1024, peer poll intvl 64
root delay 137.77 msec, root disp 142.75, reach 376, sync dist 215.363
delay 4.23 msec, offset -8.587 msec, dispersion 1.62
precision 2**19, version 3
org time AFE252E2.3AC0E887 (00:12:34.229 PDT Mon Jul 5 1993)
rcv time AFE252E2.3D7E464D (00:12:34.240 PDT Mon Jul 5 1993)
xmt time AFE25301.6F83E753 (00:13:05.435 PDT Mon Jul 5 1993)
filtdelay =     4.23    4.14    2.41    5.95    2.37    2.33    4.26    4.33
filtoffset =   -8.59   -8.82   -9.91   -8.42  -10.51  -10.77  -10.13  -10.11
filterror =     0.50    1.48    2.46    3.43    4.41    5.39    6.36    7.34

192.168.13.33 configured, selected, sane, valid, stratum 3
ref ID 192.168.1.111, time AFE24F0E.14283000 (23:56:14.078 PDT Sun Jul 4 1993)
our mode client, peer mode server, our poll intvl 128, peer poll intvl 128
root delay 83.72 msec, root disp 217.77, reach 377, sync dist 264.633
delay 4.07 msec, offset 3.483 msec, dispersion 2.33
precision 2**6, version 3
org time AFE252B9.713E9000 (00:11:53.442 PDT Mon Jul 5 1993)
rcv time AFE252B9.7124E14A (00:11:53.441 PDT Mon Jul 5 1993)
xmt time AFE252B9.6F625195 (00:11:53.435 PDT Mon Jul 5 1993)
filtdelay =     6.47    4.07    3.94    3.86    7.31    7.20    9.52    8.71
filtoffset =    3.63    3.48    3.06    2.82    4.51    4.57    4.28    4.59
filterror =     0.00    1.95    3.91    4.88    5.84    6.82    7.80    8.77

192.168.13.57 configured, our_master, sane, valid, stratum 3
ref ID 192.168.1.111, time AFE252DC.1F2B3000 (00:12:28.121 PDT Mon Jul 5 1993)
our mode client, peer mode server, our poll intvl 128, peer poll intvl 128
root delay 125.50 msec, root disp 115.80, reach 377, sync dist 186.157
delay 7.86 msec, offset 11.176 msec, dispersion 3.62
precision 2**6, version 2
org time AFE252DE.77C29000 (00:12:30.467 PDT Mon Jul 5 1993)
rcv time AFE252DE.7B2AE40B (00:12:30.481 PDT Mon Jul 5 1993)
xmt time AFE252DE.6E6D12E4 (00:12:30.431 PDT Mon Jul 5 1993)
filtdelay =    49.21    7.86    8.18    8.80    4.30    4.24    7.58    6.42
filtoffset =   11.30   11.18   11.13   11.28    8.91    9.09    9.27    9.57
filterror =     0.00    1.95    3.91    4.88    5.78    6.76    7.74    8.71   

Table 52 describes the significant fields shown in the display.

Table 52 show ntp associations detail Field Descriptions 

Field
Descriptions

configured

Peer was statically configured.

dynamic

Peer was dynamically discovered.

our_master

Local machine is synchronized to this peer.

selected

Peer is selected for possible synchronization.

candidate

Peer is a candidate for selection.

sane

Peer passes basic sanity checks.

insane

Peer fails basic sanity checks.

valid

Peer time is believed to be valid.

invalid

Peer time is believed to be invalid.

leap_add

Peer is signalling that a leap second will be added.

leap-sub

Peer is signalling that a leap second will be subtracted.

unsynced

Peer is not synchronized to any other machine.

ref ID

Address of machine peer is synchronized to.

time

Last time stamp peer received from its master.

our mode

Our mode relative to peer (active/passive/client/server/bdcast/bdcast client).

peer mode

Peer's mode relative to us.

our poll intvl

Our poll interval to peer.

peer poll intvl

Peer's poll interval to us.

root delay

Delay along path to root (ultimate stratum 1 time source).

root disp

Dispersion of path to root.

reach

Peer reachability (bit string in octal).

sync dist

Peer synchronization distance.

delay

Round-trip delay to peer.

offset

Offset of peer clock relative to our clock.

dispersion

Dispersion of peer clock.

precision

Precision of peer clock in Hertz.

version

NTP version number that peer is using.

org time

Originate time stamp.

rcv time

Receive time stamp.

xmt time

Transmit time stamp.

filtdelay

Round-trip delay (in milliseconds) of each sample.

filtoffset

Clock offset (in milliseconds) of each sample.

filterror

Approximate error of each sample.


Related Commands

Command
Description

show ntp status

Displays the status of the NTP.


show ntp status

To show the status of the Network Time Protocol (NTP), use the show ntp status EXEC command.

show ntp status

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.


Examples

The following is sample output from the show ntp status command:

Router> show ntp status

Clock is synchronized, stratum 4, reference is 192.168.13.57
nominal freq is 250.0000 Hz, actual freq is 249.9990 Hz, precision is 2**19
reference time is AFE2525E.70597B34 (00:10:22.438 PDT Mon Jul 5 1993)
clock offset is 7.33 msec, root delay is 133.36 msec
root dispersion is 126.28 msec, peer dispersion is 5.98 msec

Table 53 describes the significant fields shown in the display.

Table 53 show ntp status Field Descriptions 

Field
Description

synchronized

System is synchronized to an NTP peer.

unsynchronized

System is not synchronized to any NTP peer.

stratum

NTP stratum of this system.

reference

Address of peer the system is synchronized to.

nominal freq

Nominal frequency of system hardware clock.

actual freq

Measured frequency of system hardware clock.

precision

Precision of the clock of this system (in Hertz).

reference time

Reference time stamp.

clock offset

Offset of the system clock to synchronized peer.

root delay

Total delay along path to root clock.

root dispersion

Dispersion of root path.

peer dispersion

Dispersion of synchronized peer.


Related Commands

Command
Description

show ntp associations

Displays the status of the NTP associations.


show registry

To show the function registry information, use the show registry EXEC command.

show registry [registry-name [registry-num]] [brief | statistics]

Syntax Description

registry-name

(Optional) Name of the registry to examine.

registry-num

(Optional) Number of the registry to examine.

brief

(Optional) Displays limited functions and services information.

statistics

(Optional) Displays function registry statistics.


Defaults

brief

Command Modes

EXEC

Command History

Release
Modification

11.1

This command was introduced.


Examples

The following example is sample output of the show registry command using the brief argument:

Switch> show registry atm 3/0/0 brief

Registry objects: 1799  bytes: 213412

--
Registry 23: ATM Registry
  Service 23/0:
  Service 23/1:
  Service 23/2:
  Service 23/3:
  Service 23/4:
  Service 23/5:
  Service 23/6:
  Service 23/7:
  Service 23/8:
  Service 23/9:
  Service 23/10:
  Service 23/11:
  Service 23/12:
  Service 23/13:
  Service 23/14:

--
RegistrY 25: ATM routing Registry
  Service 25/0:

show sntp

To show information about the Simple Network Time Protocol (SNTP), use the show sntp EXEC command on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router.

show sntp

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release
Modification

11.2

This command was introduced.


Examples

The following is sample output from the show sntp command:

Router> show sntp

SNTP server     Stratum   Version    Last Receive
171.69.118.9       5         3        00:01:02 
172.21.28.34       4         3        00:00:36    Synced  Bcast

Broadcast client mode is enabled.

Table 54 describes the significant fields shown in the display.

Table 54 show sntp Field Descriptions 

Field
Description

SNTP server

Address of the configured or broadcast NTP server.

Stratum

NTP stratum of the server. The stratum indicates how far away from an authoritative time source the server is.

Version

NTP version of the server.

Last Receive

Time since the last NTP packet was received from the server.

Synced

Indicates the server chosen for synchronization.

Bcast

Indicates a broadcast server.


Related Commands

Command
Description

sntp broadcast client

Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use SNTP to accept NTP traffic from any broadcast server.

sntp server

Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use SNTP to request and accept NTP traffic from a time server.


sntp broadcast client

To use the Simple Network Time Protocol (SNTP) to accept Network Time Protocol (NTP) traffic from any broadcast server, use the sntp broadcast client global configuration command to configure a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router. To prevent the router from accepting broadcast traffic, use the no form of this command.

sntp broadcast client

no sntp broadcast client

Syntax Description

This command has no arguments or keywords.

Defaults

The router does not accept SNTP traffic from broadcast servers.

Command Modes

Global configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

SNTP is a compact, client-only version of the NTP. SNMP can only receive the time from NTP servers; it cannot be used to provide time services to other systems.

SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection.

You must configure the router with either this command or the sntp server global configuration command to enable SNTP.

Examples

The following example enables the router to accept broadcast NTP packets and shows sample show sntp command output:

Router(config)# sntp broadcast client
Router(config)# end
Router#
%SYS-5-CONFIG: Configured from console by console
Router# show sntp

SNTP server     Stratum   Version    Last Receive
172.21.28.34       4         3        00:00:36    Synced  Bcast

Broadcast client mode is enabled.

Related Commands

Command
Description

show sntp

Displays information about SNTP on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router.

sntp server

Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use SNTP to request and accept NTP traffic from a time server.


sntp server

To configure a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, Cisco 1750, or Cisco 800 router to use the Simple Network Time Protocol (SNTP) to request and accept Network Time Protocol (NTP) traffic from a stratum 1 time server, use the sntp server global configuration command. To remove a server from the list of NTP servers, use the no form of this command.

sntp server {address | hostname} [version number]

no sntp server {address | hostname}

Syntax Description

address

IP address of the time server.

hostname

Host name of the time server.

version number

(Optional) Version of NTP to use. The default is 1.


Defaults

The router does not accept SNTP traffic from a time server.

Command Modes

Global configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

SNTP is a compact, client-only version of the NTP. SNMP can only receive the time from NTP servers; it cannot be used to provide time services to other systems.

SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection.

Enter this command once for each NTP server.

You must configure the router with either this command or the sntp broadcast client global configuration command in order to enable SNTP.

SNTP time servers should operate only at the root (stratum 1) of the subnet, and then only in configurations where no other source of synchronization other than a reliable radio or modem time service is available. A stratum 2 server cannot be used as an SNTP time server. The use of SNTP rather than NTP in primary servers should be carefully considered.

Examples

The following example enables the router to request and accept NTP packets from the server at 172.21.118.9 and displays sample show sntp command output:

Router(config)# sntp server 172.21.118.9
Router(config)# end
Router# 
%SYS-5-CONFIG: Configured from console by console
Router# show sntp

SNTP server     Stratum   Version    Last Receive
172.21.118.9       5         3        00:01:02    Synced 

Related Commands

Command
Description

show sntp

Displays information about SNTP on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router.

sntp broadcast client

Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use SNTP to accept NTP traffic from any broadcast server.


time-range

To enable time-range configuration mode and define time ranges for functions (such as extended access lists), use the time-range global configuration command. To remove the time limitation, use the no form of this command.

time-range time-range-name

no time-range time-range-name

Syntax Description

time-range-name

Desired name for the time range. The name cannot contain a space or quotation mark, and must begin with a letter.


Defaults

None

Command Modes

Global configuration

Command History

Release
Modification

12.0(1)T

This command was introduced.


Usage Guidelines

The time-range entries are identified by a name, which is referred to by one or more other configuration commands. Multiple time ranges can occur in a single access list or other feature.


Note For Cisco IOS Release 12.2, IP and Internetwork Packet Exchange (IPX) extended access lists are the only functions that can use time-ranges. For further information on using these functions, see the Release 12.2 Cisco IOS IP Configuration Guide and the Release 12.2 Cisco IOS AppleTalk and Novell IPX Configuration Guide.


After the time-range command, use the periodic time-range configuration command, the absolute time-range configuration command, or some combination of them to define when the feature is in effect. Multiple periodic commands are allowed in a time range; only one absolute command is allowed.


Tip To avoid confusion, use different names for time ranges and named access lists.


Examples

The following example denies HTTP traffic on Monday through Friday from 8:00 a.m. to 6:00 p.m. The example allows UDP traffic on Saturday and Sunday from noon to midnight only.

time-range no-http
 periodic weekdays 8:00 to 18:00
!
time-range udp-yes
 periodic weekend 12:00 to 24:00
!
ip access-list extended strict
 deny tcp any any eq http time-range no-http
 permit udp any any time-range udp-yes
!
interface ethernet 0
 ip access-group strict in

Related Commands

Command
Description

absolute

Specifies an absolute start and end time for a time range.

ip access-list

Defines an IP access list by name.

periodic

Specifies a recurring (weekly) start and end time for a time range.

permit (IP)

Sets conditions under which a packet passes a named IP access list.