Table Of Contents
erase
errdisable detect cause
errdisable flap-setting cause
errdisable recovery
fabric lcd-banner
fabric required
fabric switching-mode allow
file verify auto
flowcontrol
format
fsck
hold-queue
hw-module reset
instance
interface
interface port-channel
interface range
interface vlan
ip access-list hardware permit fragments
ip auth-proxy max-login-attempts
ip auth-proxy watch-list
ip cef table consistency-check
ip flow-aggregation cache
ip flow-cache entries
ip flow-export destination
ip flow-export source
ip flow-export version
ip igmp snooping
ip igmp snooping fast-leave
ip igmp snooping l2-entry-limit
ip igmp snooping last-member-query-interval
ip igmp snooping mrouter
ip igmp snooping querier
ip igmp snooping static
ip local-proxy-arp
ip multicast rpf backoff
ip multicast rpf interval
ip pim autorp listener
ip rgmp
ip route-cache flow
ip sticky-arp
ip verify unicast reverse-path
ip verify unicast source reachable-via
ip wccp group-listen
ip wccp redirect exclude in
ip wccp web-cache accelerated
l2protocol-tunnel
l2protocol-tunnel cos
l2protocol-tunnel drop-threshold
l2protocol-tunnel shutdown-threshold
lacp port-priority
lacp system-priority
link debounce
logging event link-status (global configuration)
logging event link-status (interface configuration)
logging event subif-link-status
mac access-list extended
mac-address-table aging-time
mac-address-table static
mac-address-table unicast-flood
match
maxconns (real server configuration submode)
maximum-paths
mdix auto
mkdir disk0:
mls aclmerge algorithm
mls aging fast
mls aging long
mls aging normal
22
erase
To erase a file system, use the erase command.
erase {const_nvram: | nvram: | startup-config:}
Syntax Description
const_nvram:
|
Erases all files under the const_nvram: partition.
|
nvram:
|
Erases NVRAM.
|
startup-config:
|
Erases the contents of the configuration memory.
|
Defaults
This command has no default settings.
Command Modes
EXEC
Command History
Release
|
Modification
|
12.0(7)XE
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
Usage Guidelines
Caution 
When you use the
erase command to erase a file system, you cannot recover the files in the file system.
The erase nvram: command replaces the write erase command and the erase startup-config command.
You can use the erase command on both Class B and Class C Flash file systems only. To reclaim space on Flash file systems after deleting files using the delete command, you must use the erase command. The erase command erases all of the files in the Flash file system.
Class A Flash file systems cannot be erased. You can delete individual files using the delete command and then reclaim the space using the squeeze command. You can also use the format command to format the Flash file system.
On Class C Flash file systems, space is dynamically reclaimed when you use the delete command. You can also use either the format or erase command to reinitialize a Class C Flash file system.
The erase nvram: command erases NVRAM. On Class A file system platforms, if the CONFIG_FILE argument specifies a file in Flash memory, the specified file is marked "deleted."
You can enter the erase const_nvram command to erase the VLAN database configuration file.
Examples
This example shows how to erase the NVRAM and the startup configuration in the NVRAM:
Related Commands
boot config
delete (refer to the Cisco IOS Release 12.1 Command Reference)
more nvram:startup-config: (refer to the Cisco IOS Release 12.1 Command Reference)
show bootvar
undelete (refer to the Cisco IOS Release 12.1 Command Reference)
errdisable detect cause
To enable error-disable detection, use the errdisable detect cause command. Use the no form of this command to disable error-disable detection.
errdisable detect cause {all | dtp-flap | l2ptguard | link-flap | pagp-flap | udld}
no errdisable detect cause {all | dtp-flap | l2ptguard | link-flap | pagp-flap | udld}
errdisable detect cause <udld|bpduguard|rootguard| pagp-flap|dtp-flap|link-flap
Syntax Description
arp-inspection
|
|
bpduguard
|
Specifies detection for the BPDU guard flap error-disable cause.
|
dhcp-rate-limit
|
|
dtp-flap
|
Specifies detection for the DTP flap error-disable cause.
|
gbic-invalid
|
|
l2ptguard
|
Specifies detection for the Layer 2 protocol-tunnel error-disable cause.
|
link-flap
|
Specifies detection for the link flap error-disable cause.
|
pagp-flap
|
Specifies detection for the PAgP flap error-disable cause.
|
rootguard
|
Specifies detection for the rootguard flap error-disable cause.
|
udld
|
Specifies detection for the UDLD error-disable cause.
|
Defaults
Enabled for all causes
Command Modes
Global configuration
Command History
Release
|
Modification
|
12.1(3a)E3
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
12.1(11b)EX
|
This command was changed to support Layer 2 protocol tunneling.
|
Usage Guidelines
A cause (bpduguard, dtp-flap, link-flap, pagp-flap, root-guard, udld) is defined as the reason why the error-disabled state occurred. When a cause is detected on an interface, the interface is placed in an error-disabled state (an operational state that is similiar to the link down state).
You must enter the shutdown and then the no shutdown commands to recover an interface manually from errdisable.
Examples
This example shows how to enable error-disable detection for the Layer 2 protocol-tunnel guard error-disable cause:
Router(config)# errdisable detect cause l2ptguard
Related Commands
show errdisable detect
show interfaces status
errdisable flap-setting cause
To configure the maximum number of flaps that are allowed to occur before setting to error disable, use the errdisable flap-setting cause command. Use the no form of this command to return to the default settings.
errdisable flap-setting cause {link-flap | pagp-flap | dtp-flap} {max-flaps flap-count} {time
seconds}
Syntax Description
link-flap
|
Specifies the flap-setting values for the link flap error-disable cause.
|
pagp-flap
|
Specifies the flap-setting values for the PAgP flap error-disable cause.
|
dtp-flap
|
Specifies the flap-setting values for the DTP flap error-disable cause.
|
max-flaps flap-count
|
Specifies the maximum number of flaps that are allowed to occur before setting to error disable; valid values are from 1 to 100.
|
time seconds
|
Specifies the time period that flaps are counted; valid values are from 1 to 120 seconds.
|
Defaults
The defaults are as follows:
•
Enabled for all causes
•
flap-count—
•
seconds—300 seconds
Command Modes
Global configuration
Command History
Release
|
Modification
|
12.1(22)E2
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
Usage Guidelines
You must enter the shutdown and then the no shutdown commands to recover an interface manually from errdisable.
Examples
This example shows how to enable error-disable detection for the Layer 2 protocol-tunnel guard error-disable cause:
Router(config)# errdisable detect cause l2ptguard
Related Commands
show errdisable flap-values
errdisable recovery
To configure the recovery mechanism, use the errdisable recovery command. Use the no form of this command to return to the default settings.
errdisable recovery cause {all | bpduguard | channel-misconfig | dhcp-rate-limit | dtp-flap |
gbic-invalid | l2ptguard | link-flap | pagp-flap | pesecure-violation | security-violation | udld
| unicast-flood}
errdisable recovery {interval interval}
no errdisable recovery cause {all | bpduguard | channel-misconfig | dhcp-rate-limit | dtp-flap |
gbic-invalid | l2ptguard | link-flap | pagp-flap | pesecure-violation | security-violation | udld
| unicast-flood}
no errdisable recovery {interval interval}
Syntax Description
cause
|
Enables error-disable recovery to recover from a specific cause.
|
all
|
Enables the recovery timers for all error-disable causes.
|
bpduguard
|
Enables the recovery timer for the BPDU guard error-disable cause.
|
channel-misconfig
|
Enables the recovery timer for the channel-misconfig error-disable cause.
|
dhcp-rate-limit
|
Enables the recovery timer for the DHCP rate limit error-disable cause.
|
dtp-flap
|
Enables the recovery timer for the DTP flap error-disable cause.
|
gbic-invalid
|
Enables the recovery timer for the GBIC invalid error-disable cause.
|
l2ptguard
|
Enables the recovery timer for the Layer 2 protocol-tunnel error-disable cause.
|
link-flap
|
Enables the recovery timer for the link-flap error-disable cause.
|
pagp-flap
|
Enables the recovery timer for the PAgP-flap error-disable cause.
|
pesecure-violation
|
Enables the recovery timer for the pesecure violation error-disable cause.
|
security-violation
|
Enables automatic recovery of ports disabled due to 802.1x security violations.
|
udld
|
Enables the recovery timer for the UDLD error-disable cause.
|
unicast-flood
|
Enables the recovery timer for the unicast flood error-disable cause.
|
interval interval
|
Specifies the time to recover from a specified error-disable cause; valid values are from 30 to 86400 seconds.
|
Defaults
The defaults are as follows:
•
Disabled for all causes.
•
If enabled, the interval is 300 seconds.
Command Modes
Global configuration
Command History
Release
|
Modification
|
12.0(7)XE
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
12.1(2)
|
The information display for the command was updated.
|
12.1(8a)E
|
Support for this command on the Catalyst 6500 series switches was extended to the 12.1 E release.
|
12.1(11b)EX
|
This command was changed to support Layer 2 protocol tunneling.
|
Usage Guidelines
A cause (bpduguard, dhcp-rate-limit, dtp-flap, l2ptguard, link-flap, pagp-flap, security-violation, channel-misconfig, psecure-violation, udld, or unicast-flood) is defined as the reason why the error-disabled state occurred. When a cause is detected on an interface, the interface is placed in an error-disabled state (an operational state that is similiar to the link down state). If you do not enable errdisable recovery for the cause, the interface stays in the error-disabled state until a shutdown and no shutdown occurs. If you enable recovery for a cause, the interface is brought out of the error-disabled state and allowed to retry operation again once all the causes have timed out.
You must enter the shutdown and then the no shutdown commands to recover an interface manually from errdisable.
Examples
This example shows how to enable the recovery timer for the BPDU guard error-disable cause:
Router(config)# errdisable recovery cause bpduguard
This example shows how to set the timer to 300 seconds:
Router(config)# errdisable recovery interval 300
Related Commands
show errdisable detect
show interfaces status
fabric lcd-banner
Use the fabric lcd-banner command to specify the message-of-the-day (MOTD) banner for display on the Switch Fabric Module. Use the no form of this command to delete the MOTD banner.
fabric lcd-banner d message d
no fabric lcd-banner
Syntax Description
d
|
Delimiting character; see the "Usage Guidelines" section for additional guidelines.
|
message
|
Message text; see the "Usage Guidelines" section for additional guidelines.
|
Defaults
The default is that no MOTD banner is specified.
Command Modes
Global configuration mode
Command History
Release
|
Modification
|
12.1(8a)EX
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
Usage Guidelines
You cannot use the delimiting character in the banner message. The delimiter is a character of your choice—a pound sign (#), for example.
You can replace tokens with the corresponding configuration argument.
Follow this command with one or more blank spaces and a delimiting character of your choice. Then enter one or more lines of text, terminating the message with the second occurrence of the delimiting character.
This MOTD banner is useful for displaying messages that affect all users (such as impending system shutdowns).
When you connect to the router, the MOTD banner appears before the login prompt. After you successfully log in to the router, the EXEC banner or incoming banner is displayed, depending on the type of connection. For a reverse Telnet login, the incoming banner is displayed. For all other connections, the router displays the EXEC banner.
To customize the banner, use tokens in the form $(token) in the message text. Tokens display current Cisco IOS configuration arguments, such as the router's host name and IP address.
Table 2-8 describes the command tokens.
Table 2-8 Command Tokens
Token
|
Information Displayed in the Banner
|
$(hostname)
|
Displays the router's host name.
|
$(domain)
|
Displays the router's domain name.
|
$(line)
|
Displays the VTY or TTY (async) line number.
|
$(line-desc)
|
Displays the description attached to the line.
|
Examples
This example shows how to set a MOTD banner for display on the Switch Fabric Module LCD display; the pound sign (#) is used as a delimiting character:
Router (config)# fabric lcd-banner#
Building power will be off from 7:00 AM until 9:00 AM this coming Tuesday.
This example shows how to set a MOTD banner; the percent sign (%) is used as a delimiting character:
Router (config)# fabric lcd-banner%
Enter TEXT message. End with the character '%'.
You have entered $(hostname).$(domain) on line $(line) ($(line-desc)) %
When the MOTD banner is executed, you see the following. Notice that the $(token) syntax is replaced by the corresponding configuration argument:
You have entered darkstar.ourdomain.com on line 5 (Dialin Modem)
Related Commands
banner exec (refer to the Cisco IOS Release 12.1 Command Reference)
banner incoming (refer to the Cisco IOS Release 12.1 Command Reference)
banner login (refer to the Cisco IOS Release 12.1 Command Reference)
banner slip-ppp (refer to the Cisco IOS Release 12.1 Command Reference)
exec-banner (refer to the Cisco IOS Release 12.1 Command Reference)
motd-banner (refer to the Cisco IOS Release 12.1 Command Reference)
fabric required
To prevent the switch from coming online without a Switch Fabric Module, use the fabric required command. Use the no form of this command to allow the switch to come up without a Switch Fabric Module.
fabric required
no fabric required
Syntax Description
This command has no arguments or keywords.
Defaults
The switch does not require a Switch Fabric Module.
Command Modes
Global configuration
Command History
Release
|
Modification
|
12.1(11b)E
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
Usage Guidelines
This command is not supported on systems configured with a Supervisor Engine 1.
If you enter the fabric required command when the last Switch Fabric Module is removed or powered down, all modules, except the supervisor engine, will power down. When you insert or power on the first Switch Fabric Module, the modules that were previously powered down will power up if the Switch Fabric Module configuration is not in conflict with other configurations.
If you enter the no fabric required command, modules will also power on if a Switch Fabric Module is not present and the configuration allows for it.
Examples
This example shows how to allow the switch coming online with (or without) a Switch Fabric Module:
Router (config)# fabric required
Related Commands
show fabric
fabric switching-mode allow
To enable truncated mode in the presence of two or more fabric-enabled switching modules, use the fabric switching-mode allow command. Use the no form of this command to disable truncated mode.
fabric switching-mode allow {bus-mode | {truncated [{threshold [mod]}]}}
no fabric switching-mode allow {bus-mode | {truncated [threshold]}}
Syntax Description
bus-mode
|
Specifies bus-only mode.
|
truncated
|
Specifies truncated mode.
|
threshold mod
|
(Optional) Number of Switch Fabric Module-capable modules that are needed for truncated switching; see the "Usage Guidelines" section for additional information.
|
Defaults
The truncated mode is disabled.
Command Modes
Global configuration
Command History
Release
|
Modification
|
12.1(11b)E
|
Support for this command was introduced on the Supervisor Engine 2.
|
Usage Guidelines
Bus mode—The switch uses this mode for traffic between nonfabric-enabled modules and for traffic between a nonfabric-enabled module and a fabric-enabled module. In this mode, all traffic passes between the local bus and the supervisor engine bus.
Truncated mode—The switch uses this mode for traffic between fabric-enabled modules when there are both fabric-enabled and nonfabric-enabled modules installed. In this mode, the switch sends a truncated version of the traffic (the first 64 bytes of the frame) over the switch fabric channel.
Compact mode—The switch uses this mode for all traffic when only fabric-enabled modules are installed. In this mode, a compact version of the DBus header is forwarded over the switch fabric channel, which provides the best possible performance.
To prevent use of nonfabric-enabled modules or to prevent fabric-enabled modules from using bus mode, enter the no fabric switching-mode allow bus-mode command.
Caution 
Entering the
no fabric switching-mode allow bus-mode command removes power from any nonfabric-enabled modules installed in the switch.
The fabric switching-mode allow command affects switches configured with a minimum of two fabric-enabled modules.
You can enter the fabric switching-mode allow truncated command to unconditionally allow truncated mode.
You can enter the no fabric switching-mode allow truncated command to allow truncated mode if the threshold is met.
You can enter the no fabric switching-mode allow bus-mode command to prevent any module from running in bus-mode.
To return to the default truncated-mode threshold, enter the no fabric switching-mode allow truncated threshold command.
The valid value for mod is the threshold value.
Examples
This example shows how to specify truncated mode:
Router (config)# fabric switching-mode allow truncated
Related Commands
show fabric
file verify auto
To verify the compressed Cisco IOS image checksum, use the file verify auto command. Use the no form of this command to turn off automatic verification after a copy operation.
file verify auto
no file verify auto
Syntax Description
This command has no arguments or keywords.
Defaults
Verification is done automatically after completion of a copy operation.
Command Modes
Global configuration
Command History
Release
|
Modification
|
12.1(19)E
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
Usage Guidelines
Enter the copy /noverify command to override the default behavior for a single copy operation.
Examples
This example shows how to verify the compressed Cisco IOS image checksum:
Router(config)# file verify auto
Related Commands
copy /noverify
verify
flowcontrol
To configure a port to send or receive pause frames, use the flowcontrol command.
flowcontrol {send | receive} {desired | off | on}
Syntax Description
send
|
Specifies that a port sends pause frames.
|
receive
|
Specifies that a port processes pause frames.
|
desired
|
Obtains predictable results regardless of whether a remote port is set to on, off, or desired.
|
off
|
Prevents a local port from receiving and processing pause frames from remote ports or from sending pause frames to remote ports.
|
on
|
Enables a local port to receive and process pause frames from remote ports or send pause frames to remote ports.
|
Defaults
Flow-control defaults depend upon port speed. The defaults are as follows:
•
Gigabit Ethernet ports default to off for receive and desired for send.
•
Fast Ethernet ports default to off for receive and on for send.
•
On the 24-port 100BASE-FX and 48-port 10/100 BASE-TX RJ-45 modules, the default is off for receive and off for send.
•
10-Gigabit Ethernet ports are permanently configured to respond to pause frames and the default for send is off.
Command Modes
Interface configuration
Command History
Release
|
Modification
|
12.1(8b)EX2
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
12.1(13)E
|
Support for this command on the Catalyst 6500 series switches was extended to the 12.1 E release.
|
Usage Guidelines
The send and desired keywords are supported on Gigabit Ethernet ports only.
Pause frames are special packets that signal a source to stop sending frames for a specific period of time because the buffers are full.
Gigabit Ethernet ports on the Catalyst 6500 series switches use flow control to inhibit the transmission of packets to the port for a period of time; other Ethernet ports use flow control to respond to flow-control requests.
If a Gigabit Ethernet port receive buffer becomes full, the port transmits a "pause" packet that tells remote ports to delay sending more packets for a specified period of time. All Ethernet ports (1000 Mbps, 100 Mbps, and 10 Mbps) can receive and act upon "pause" packets from other devices.
You can configure non-Gigabit Ethernet ports to ignore received pause frames (disable) or to react to them (enable).
When used with receive, the on and desired keywords have the same result.
All Catalyst 6500 series switch Gigabit Ethernet ports can receive and process pause frames from remote devices.
To obtain predictable results, follow these guidelines:
•
Use send on only when remote ports are set to receive on or receive desired.
•
Use send off only when remote ports are set to receive off or receive desired.
•
Use receive on only when remote ports are set to send on or send desired.
•
Use send off only when remote ports are set to receive off or receive desired.
Examples
These examples show how to configure the local port to not support any level of flow control by the remote port:
Router(config-if)# flowcontrol receive off
Router(config-if)# flowcontrol send off
Related Commands
show interfaces flowcontrol
format
To format a Class A or Class C Flash file system, use the format command.
Class A Flash file system:
format bootflash: [spare spare-number] filesystem1: [[filesystem2:][monlib-filename]]
Class C Flash file system:
format filesystem1:
Caution 
Reserve a certain number of memory sectors as spares, so that if some sectors fail, most of the Flash PC card can still be used. Otherwise, you must reformat the Flash PC card when some of the sectors fail.
Syntax Description
spare spare-number
|
(Optional) Number of the spare sectors to reserve on formatted Flash memory; valid values are from 0 to 16.
|
filesystem1:
|
File system to format; valid values are disk0:, bootflash:, slot0:, and sup-bootflash:; see the "Usage Guidelines" section for additional information.
|
filesystem2:
|
(Optional) File system containing the monlib file to use for formatting filesystem1 followed by a colon.
|
monlib-filename
|
(Optional) Name of the ROM monitor library file (monlib file) to use for formatting the filesystem1 argument.
When used with HSA and you do not specify the monlib-filename argument, the system takes the ROM monitor library file from the slave image bundle. If you specify the monlib-filename argument, the system assumes that the files reside on the slave devices.
|
Defaults
The defaults are as follows:
•
monlib-filename is the one bundled with the system software.
•
spare-number is zero (0).
Command Modes
EXEC
Command History
Release
|
Modification
|
12.0(7)XE
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
12.1(1)E
|
Support for this command on the Catalyst 6500 series switches was extended to the 12.1 E release.
|
12.1(8a)EX
|
This command was changed to support the disk0: keyword.
|
Usage Guidelines
Use this command to format Class A or C Flash memory file systems.
disk0: is a Class C file system.
bootflash:, slot0:, and sup-bootflash: are Class A file systems.
In some cases, you might need to insert a new Flash PC card and load images or back up configuration files onto it. Before you can use a new Flash PC card, you must format it.
Sectors in Flash PC cards can fail. Reserve certain Flash PC sectors as "spares" by using the optional spare argument on the format command to specify between 0 and 16 sectors as spares. If you reserve a small number of spare sectors for emergencies, you can still use most of the Flash PC card. If you specify 0 spare sectors and some sectors fail, you must reformat the Flash PC card, which erases all existing data.
The monlib file is the ROM monitor library. The ROM monitor uses this file to access files in the Flash file system. The Cisco IOS system software contains a monlib file.
In the command syntax, filesystem1: specifies the device to format, and filesystem2: specifies the optional device containing the monlib file, used to format filesystem1:. If you omit the optional filesystem2: and monlib-filename arguments, the system formats filesystem1:, using the monlib file already bundled with the system software. If you omit only the optional filesystem2: argument, the system formats filesystem1:, using the monlib file from the device that you specified with the cd command. If you omit only the optional monlib-filename argument, the system formats filesystem1: using filesystem2:'s monlib file. When you specify both arguments—filesystem2: and monlib-filename—the system formats filesystem1:, using the monlib file from the specified device. You can specify filesystem1:'s own monlib file in this argument. If the system cannot find a monlib file, it terminates its formatting.
The disk0: keyword is supported on systems configured with a Supervisor Engine 2 only.
Examples
This example shows how to format a Flash PC card inserted in slot 0:
Running config file on this device, proceed? [confirm]y
All sectors will be erased, proceed? [confirm]y
Enter volume id (up to 31 characters): <Return>
Formatting sector 1 (erasing)
Format device slot0 completed
When the console returns to the EXEC prompt, the new Flash PC card is successfully formatted and ready for use.
Related Commands
cd
copy (refer to the Cisco IOS Release 12.1 Command Reference)
delete (refer to the Cisco IOS Release 12.1 Command Reference)
show file system (refer to the Cisco IOS Release 12.1 Command Reference)
undelete (refer to the Cisco IOS Release 12.1 Command Reference)
fsck
To check a Flash file system for damage and to repair any problems, use the fsck command.
fsck [/automatic | disk0: | slavedisk0:]
Syntax Description
/automatic
|
(Optional) Specifies automatic mode; see the "Usage Guidelines" section for additional information.
|
disk0:
|
(Optional) Specifies the file system to check.
|
slavedisk0:
|
(Optional) Specifies the file system on the redundant supervisor engine to check.
|
Defaults
The current file system is checked if disk0: is not specified.
Command Modes
EXEC
Command History
Release
|
Modification
|
12.1(11b)E
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
Usage Guidelines
The disk0: or slavedisk0: file systems are the only file systems in the Catalyst 6500 series switches on which fsck can be run. The slavedisk0: option appears in redundant supervisor engine systems only.
This command is valid only on Class C Flash file systems and only on PCMCIA ATA Flash disks and CompactFlash disks.
The output for the fsck slavedisk0: command is similar to the fsck disk0: command output.
If you do not enter any arguments, the current file system is used. Use the pwd command to display the current file system.
If you enter the disk0: or slavedisk0: option, the fsck utility checks the selected file system for problems. If a problem is detected, a prompt is displayed asking if you want the problem fixed.
If you enter the /automatic keyword, you are prompted to confirm that you want the automatic mode. In automatic mode, problems are fixed automatically and you are not prompted to confirm.
Table 2-9 lists the checks and actions performed by the fsck utility.
Table 2-9 fsck Utility Checks and Actions
Checks
|
Actions
|
Checks the boot sector and the partition table and reports the errors.
|
No action.
|
Validates the media with the signature in the last 2 bytes of the first sector (0x55 and 0xaa, respectively).
|
No action.
|
Checks the os_id to find whether this is a FAT-12 or FAT-16 file system (valid values include 0, 1, 4, and 6).
|
No action.
|
Checks the number of FAT's field (correct values are 1 and 2).
|
No action.
|
Checks these values:
• n_fat_sectors cannot be less than 1.
• n_root_entries cannot be less than 16.
• n_root_sectors cannot be less than 2.
• base_fat_sector, n_sectors_per_cluster, n_heads, n_sectors_per_track is not 0.
|
No action.
|
Checks the files and FAT for these errors:
|
Checks the FAT for invalid cluster numbers.
|
If the cluster is a part of a file chain, the cluster is changed to end of file (EOF). If the cluster is not part of a file chain, it is added to the free list and unused cluster chain. Table 2-10 lists valid cluster numbers; numbers other than those listed in Table 2-10 are invalid numbers.
|
Checks the file's cluster chain for loops.
|
If the loop is broken, the file is truncated at the cluster where the looping occurred.
|
Checks the directories for nonzero size fields.
|
If directories are found with nonzero size fields, the size is reset to zero.
|
Checks for invalid start cluster file numbers.
|
If the start cluster number of a file is invalid, the file is deleted.
|
Checks files for bad or free clusters.
|
If the file contains bad or free clusters, the file is truncated at the last good cluster; for example, the cluster that points to this bad/free cluster.
|
Checks to see if the file's cluster chain is longer than indicated by the size fields.
|
If the file's cluster chain is longer than indicated by the size fields, the file size is recalculated and the directory entry is updated.
|
Checks to see if two or more files share the same cluster (crosslinked).
|
If two or more files are crosslinked, you are prompted to accept the repair, and one of the files is truncated.
|
Checks to see if the file's cluster chain is shorter than indicated by the size fields.
|
If the file's cluster chain is shorter than indicated by the size fields, the file size is recalculated and the directory entry is updated.
|
Checks to see if there are any unused cluster chains.
|
If unused cluster chains are found, new files are created and linked to that file with the name fsck-<start cluster>.
|
Table 2-10 Valid Cluster Numbers
Cluster
|
FAT-12
|
FAT-16
|
Next entry in the chain
|
2-FEF
|
2-FFEF
|
Last entry in chain
|
FF8-FFF
|
FFF8-FFFF
|
Available cluster
|
0
|
0
|
Bad Cluster
|
FF7
|
FFF7
|
Examples
This example shows how to run a check of the current file system:
Checking the boot sector and partition table...
Checking FAT, Files and Directories...
Press 1/2 to truncate or any other character to ignore[confirm] q
Ignoring this error and continuing with the rest of the check...
Press 1/2 to truncate or any other character to ignore[confirm] 1
File disk0:/FILE5 truncated.
Press 1/2 to truncate or any other character to ignore[confirm] 2
File disk0:/FILE6 truncated.
Size of File disk0:/FILE7 recalculated.
File disk0:/FILE8 has a invalid cluster, truncate ?[confirm] y
Press 1/2 to truncate or any other character to ignore[confirm] i
Ignoring this error and continuing with the rest of the check...
Reclaiming unused space...
Created file disk0:/fsck-11 for an unused cluster chain
Created file disk0:/fsck-20 for an unused cluster chain
Created file disk0:/fsck-30 for an unused cluster chain
Created file disk0:/fsck-35 for an unused cluster chain
Created file disk0:/fsck-40 for an unused cluster chain
Created file disk0:/fsck-46 for an unused cluster chain
Created file disk0:/fsck-55 for an unused cluster chain
Created file disk0:/fsck-62 for an unused cluster chain
Created file disk0:/fsck-90 for an unused cluster chain
hold-queue
To limit the size of the IP output queue on an interface, use the hold-queue command. Use the no form of this command to restore the default settings for an interface.
hold-queue length {in | out}
no hold-queue {in | out}
Syntax Description
length
|
Specifies the maximum number of packets in the queue; valid values are from 0 to 65535.
|
in
|
Specifies the input queue.
|
out
|
Specifies the output queue.
|
Defaults
The defaults are as follows:
•
The default input hold-queue limit is 75 packets.
•
The default output hold-queue limit is 40 packets.
•
The default input hold-queue and output hold-queue limits for asynchronous interfaces are 10 packets.
Command Modes
Interface configuration
Command History
Release
|
Modification
|
12.0(7)XE
|
This command was introduced.
|
12.1(1)E
|
Support for this command on the Catalyst 6500 series switches was extended to the 12.1 E release. This command was changed to include the no hold-queue option.
|
Usage Guidelines
This command is not supported on the OSM.
The default limits prevent a malfunctioning interface from consuming an excessive amount of memory. There is no fixed upper limit to a queue size.
The default of 10 packets allows the Cisco IOS software to queue a number of back-to-back routing updates. This is the default for asynchronous interfaces only; other media types have different defaults.
Hold Queues and Priority Queueing
The hold queue stores packets that are received from the network and are waiting to be sent to the client. We recommend that the queue size does not exceed ten packets on asynchronous interfaces. For most other interfaces, the queue length should not exceed 100 packets.
The input hold queue prevents a single interface from flooding the network server with too many input packets. Further input packets are discarded if the interface has too many outstanding input packets in the system.
If you use priority output queueing, you can set the length of the four output queues using the priority-list global configuration command. However, you cannot use the hold-queue command to set an output hold-queue length in this situation.
For slow links, use a small output hold-queue limit. This approach prevents storing packets at a rate that exceeds the transmission capability of the link. For fast links, use a large output hold-queue limit. A fast link may be busy for a short time (and require the hold queue), but can empty the output hold queue quickly when capacity returns.
To display the current hold-queue setting and the number of packets that are discarded because of hold-queue overflows, use the show interfaces command in EXEC mode.
Caution 
Increasing the hold queue can cause negative effects to network routing and response times. If you use protocols that have seq/ack packets to determine round-trip times, do not increase the output queue. Instead, we recommend that you program the switch to drop packets and inform the hosts to slow down transmissions to match the available bandwidth. We do not recommend that you make duplicate copies of the same packet within the network (which can happen with large hold queues).
Examples
This example sets a small input queue on a slow serial line:
Router(config)# interface serial 0
Router(config-if)# hold-queue 30 i
Related Commands
priority-list (refer to the Cisco IOS Release 12.1 Command Reference)
show interfaces
hw-module reset
To reset a module by turning the power off and then on, use the hw-module reset command.
hw-module {module num} reset
Syntax Description
module num
|
Applies the command to a specific module; see the "Usage Guidelines" section for valid values.
|
Defaults
This command has no default settings.
Command Modes
Privileged EXEC
Command History
Release
|
Modification
|
12.1(5c)EX
|
Support for this command was introduced on the Supervisor Engine 2.
|
12.1(8a)E
|
Support for this command on the Supervisor Engine 2 was extended to the 12.1 E release.
|
Usage Guidelines
The num argument designates the module number. Valid values depend on the chassis used. For example, if you have a 13-slot chassis, valid values for the module number are from 1 to 13.
Examples
This example shows how to reload a specific module:
Router # hw-module module 3 reset
instance
To map a VLAN or a set of VLANs to an MST instance, use the instance command. Use the no form of this command to return the VLANs to the default instance (CIST).
instance instance-id {vlans vlan-range}
no instance instance-id
Syntax Description
instance-id
|
Instance to which the specified VLANs are mapped; valid values are from 0 to 15.
|
vlans vlan-range
|
Number of the VLANs to be mapped to the specified instance. The number is entered as a single value or a range; valid values are from 1 to 4094.
|
Defaults
No VLANs are mapped to any MST instance (all VLANs are mapped to the CIST instance).
Command Modes
MST configuration submode
Command History
Release
|
Modification
|
12.1(11b)EX
|
Support for this command was introduced on the Catalyst 6500 series switches.
|
12.1(13)E
|
Support for this command on the Catalyst 6500 series switches was extended to the 12.1 E release.
|
Usage Guidelines
The mapping is incremental, not absolute. When you enter a range of VLANs, this range is added or removed to the existing ones.
Any unmapped VLAN is mapped to the CIST instance.
If your system is configured with a Supervisor Engine 1, valid values for vlan-id are from 1 to 1005. If your system is configured with a Supervisor Engine 2, valid values for vlan-id are from 1 to 4094. Extended-range VLANs are not supported on systems configured with a Supervisor Engine 1.
Examples
This example shows how to map a range of VLANs to instance 2:
Router(config-mst)# instance 2 vlans 1-100
This example shows how to map a VLAN to instance 5:
Router(config-mst)# instance 5 vlans 1100
This example shows how to move a range of VLANs from instance 2 to the CIST instance:
Router(config-mst)# no instance 2 vlans 40-60
This example shows how to move all the VLANs mapped to instance 2 back to the CIST instance:
Router(config-mst)# no instance 2
Related Commands
name
revision
show
show spanning-tree mst
spanning-tree mst configuration
interface
To select an interface to configure and enter interface configuration mode, use the interface command.
interface type number
Syntax Description
type
|
Type of interface to be configured; see Table 2-11 for valid values.
|
number
|
Module and port number.
|
Defaults
No interface types are configured.
Command Modes
Global configuration
Command History