Contents
NTP Commands on Cisco IOS XR Software
This chapter describes the Cisco IOS XR Network Time Protocol (NTP) commands used to perform basic network time management tasks, including synchronizing time settings and coordinating time distribution over the network.
When an NTP server or client is configured, NTP features are available on all router interfaces. NTP features can be disabled for any specified interface, local or remote, to the route processor (RP).
For detailed information about NTP concepts, configuration tasks, and examples, see the Implementing NTP on Cisco IOS XR Software configuration module in Cisco IOS XR System Management Configuration Guide for the Cisco XR 12000 Series Router.
- access-group (NTP)
- authenticate (NTP)
- authentication-key (NTP)
- broadcast
- broadcast client
- broadcastdelay
- interface (NTP)
- master
- max-associations
- multicast client
- multicast destination
- ntp
- ntp clear
- ntp reset drift
- peer (NTP)
- server (NTP)
- show calendar
- show ntp associations
- show ntp status
- source (NTP)
- trusted-key
- update-calendar
access-group (NTP)
To control access to Network Time Protocol (NTP) services for an IPv4 or IPv6 access list, use the access-group command in one of the NTP configuration modes. To remove the access-group command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
access-group [ vrf vrf-name ] [ ipv4 | ipv6 ] { peer | query-only | serve | serve-only } access-list-name
no access-group [ vrf vrf-name ] [ ipv4 | ipv6 ] { peer | query-only | serve | serve-only }
Syntax Description
vrf vrf-name (Optional) Applies the access control configuration to a specified nondefault VRF. If not specified, the configuration is applied to the default VRF.
ipv4 (Optional) Specifies an IPv4 access list (default).
ipv6 (Optional) Specifies an IPv6 access list.
peer Allows time requests and NTP control queries and allows a networking device to synchronize to the remote system.
query-only Allows only NTP control queries. Cisco IOS XR software uses NTP Version 4, but the RFC for Version 3 (RFC 1305: Network Time Protocol (Version 3)—Specification, Implementation and Analysis) still applies.
serve Allows time requests and NTP control queries, but does not allow the networking device to synchronize to the remote system.
serve-only Allows only time requests.
access-list-name Name of an IPv4 or IPv6 access list.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
The access group options are scanned in the following order from least restrictive to most restrictive:
peer—Allows time requests and NTP control queries and allows the router to synchronize itself to a system whose address passes the access list criteria.
serve—Allows time requests and NTP control queries, but does not allow the router to synchronize itself to a system whose address passes the access list criteria.
serve-only—Allows only time requests from a system whose address passes the access list criteria.
query-only—Allows only NTP control queries from a system whose address passes the access list criteria.
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.
If you use the access-group command in a VRF-specific NTP configuration mode, the command is applied to the specific VRF. If you are not in a VRF-specific NTP configuration mode, the command is applied to the default VRF unless you use the vrf vrf-name keyword and argument to specify a VRF.
Task ID
Examples
The following example shows how to configure the router to allow itself to be synchronized by a peer from an IPv4 access list named access1 and to restrict access to allow only time requests from an IPv4 access list named access2:
RP/0/0/CPU0:router(config-ntp)# access-group peer access1 RP/0/0/CPU0:router(config-ntp)# access-group serve-only access2The following example shows how to configure the router to allow itself to be synchronized by peers from the IPv6 access list named access20 that route through the vrf10 VRF:
RP/0/0/CPU0:router(config-ntp)# access-group vrf vrf10 ipv6 peer access20authenticate (NTP)
To enable Network Time Protocol (NTP) authentication, use the authenticate command in NTP configuration mode. To restore the system to its default condition, use the no form of this command.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the authenticate command to enable NTP authentication. When NTP authentication is enabled, the system does not synchronize to a time source unless it carries one of the authentication keys specified by the trusted-key command. Packets failing the authentication check are dropped.
Task ID
Examples
The following example shows how to configure the system to synchronize only to a system that provides an authentication key 42 in its NTP packets:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# authenticate RP/0/0/CPU0:router(config-ntp)# authentication-key 42 md5 clear key1 RP/0/0/CPU0:router(config-ntp)# trusted-key 42authentication-key (NTP)
To define an authentication key for a trusted Network Time Protocol (NTP) time source, use the authentication-key command in NTP configuration mode. To restore the system to its default condition, use the no form of this command.
Syntax Description
key-number Authentication key. A number in the range from 1 to 65535.
md5 Provides message authentication support using the Message Digest 5 (MD5) algorithm.
clear (Optional) Specifies that the key value entered after this keyword is unencrypted.
encrypted (Optional) Specifies that the key value entered after this keyword is encrypted.
key-name Key value. The maximum length is 32 characters.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the authentication-key command to define authentication keys for use with trusted NTP time sources.
Note
When this command is written to NVRAM, the key is encrypted so that it is not displayed when the configuration is displayed.
Task ID
Examples
The following example shows how to configure the system to synchronize only to systems providing authentication key 42 in their NTP packets:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# authenticate RP/0/0/CPU0:router(config-ntp)# authentication-key 42 md5 clear key1 RP/0/0/CPU0:router(config-ntp)# trusted-key 42broadcast
To create a Network Time Protocol (NTP) broadcast server on a specified NTP interface, use the broadcast command in NTP interface configuration mode. To remove the command from the configuration file and restore the system to its default condition, use the no form of this command.
broadcast [ destination ip-address ] [ key key-id ] [ version number ]
no broadcast [ destination ip-address ] [ key key-id ] [ version number ]
Syntax Description
destination ip-address (Optional) Specifies the host IPv4 address.
key key-id (Optional) Defines the authentication key, where key-id is the authentication key to use when sending packets to this peer. The key identified by the key-id value is also used for packets received from the peer.
version number (Optional) Specifies a number from 1 to 4, indicating the NTP version.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the broadcast command to create an NTP broadcast server on an NTP interface to send NTP broadcast packets.
Use the broadcast client command to set a specific interface to receive NTP broadcast packets.
Task ID
Examples
The following example shows how to configure Packet-over-SONET/SDH (POS) interface 0/0/0/1 to send NTP packets to destination host IP address 10.0.0.0:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# interface POS 0/0/0/1 RP/0/0/CPU0:router(config-ntp-int)# broadcast destination 10.0.0.0broadcast client
To allow a networking device to receive Network Time Protocol (NTP) broadcast packets on an interface, use the broadcast client command in NTP interface configuration mode. To remove the configuration and restore the system to its default condition, use the no form of this command.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the broadcast client command to configure and create an NTP broadcast client and to associate the client with an interface to receive and handle NTP broadcast packets. If no NTP client has been created for an interface, the received NTP broadcast packets are dropped. Use this command to allow the system to listen to broadcast packets on an interface-by-interface basis.
Task ID
Examples
The following example shows how to configure Packet-over-SONET/SDH (POS) interface 0/0/0/1 to send NTP packets:
RP/0/0/CPU0:router(config)# ntp interface POS 0/0/0/1 RP/0/0/CPU0:router(config-ntp-int)# broadcast clientbroadcastdelay
To set the estimated round-trip delay between a Network Time Protocol (NTP) client and an NTP broadcast server, use the broadcastdelay command in NTP configuration mode. To restore the system to its default condition, use the no form of this command.
Syntax Description
microseconds Estimated round-trip time for NTP broadcasts, in microseconds. The range is from 1 to 999999. The default is 3000.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the broadcastdelay command to change the default round-trip delay time on a networking device that is configured as a broadcast client.
Task ID
interface (NTP)
To enter a Network Time Protocol (NTP) interface mode and run NTP interface configuration commands, use the interface command in one of the NTP configuration modes. To remove an NTP interface configuration, use the no form of this command.
interface type interface-path-id [ vrf vrf-name ] [disable]
no interface type interface-path-id [disable]
Syntax Description
type Interface type. For more information, use the question mark (?) online help function.
interface-path-id Physical interface or virtual interface.
Note Use the show interfaces command to see a list of all interfaces currently configured on the router.
For more information about the syntax for the router, use the question mark (?) online help function.
vrf vrf-name (Optional) Applies the interface configuration to a specific nondefault VRF.
disable (Optional) Disables NTP on the specified interface.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
Support was added for the vrf keyword and the vrf-name argument.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the interface command to place the router in NTP interface configuration mode, from which NTP broadcast and multicast servers and clients can be configured. By default, after the NTP process is started, NTP features become available for all interfaces. To exit NTP interface configuration mode, use the exit command.
If you use the interface command in a VRF-specific NTP configuration mode, the command is applied to the specific VRF. If you are not in a VRF-specific NTP configuration mode, the command is applied to the default VRF unless you use the vrf vrf-name keyword and argument to specify a VRF.
By default, NTP is enabled on every interface. To disable NTP on a specific interface, use the interface command with the disable keyword. To reenable NTP on an interface, use the no form of the interface command with the disable keyword.
Task ID
Examples
The following example shows how to enter NTP configuration mode, specify an NTP interface to be configured, and enter NTP interface configuration mode:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# interface POS 0/1/0/0 RP/0/0/CPU0:router(config-ntp-int)#The following example shows how to enter a VRF-specific NTP interface configuration mode:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# interface TenGiGE 0/1/1/0 vrf vrf_10 RP/0/0/CPU0:router(config-ntp-int)#The following example shows a different way to enter a VRF-specific NTP interface configuration mode:
RP/0/0/CPU0:router(config)# ntp vrf vrf_10 RP/0/0/CPU0:router(config-ntp-vrf)# interface TenGigE 0/1/1/0 RP/0/0/CPU0:router(config-ntp-int)#master
To configure the router to use its own Network Time Protocol (NTP) master clock to synchronize with peers when an external NTP source becomes unavailable, use the master command in NTP configuration mode. To restore the system to its default condition, use the no form of this command.
Syntax Description
stratum (Optional) NTP stratum number that the system claims. Range is from 1 to 15. The default is 8.
Command Default
By default, the master clock function is disabled. When the function is enabled, the default stratum is 8.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
NTP uses the concept of a “stratum” to describe how many NTP “hops” away a machine is from an authoritative time source. A stratum 1 time server has a radio or atomic clock attached directly. A stratum 2 time server receives its time through NTP from a stratum 1 time server, a stratum 3 from a stratum 2, and so on.
Caution
Use the master command with extreme caution. It is easy to override other valid time sources using this command, especially if a low-stratum number is configured. Configuring multiple machines in the same network with the master command can lead to instability in time-keeping if the machines do not agree on the time.
The networking device is normally synchronized, directly or indirectly, with an external system that has a clock. Cisco IOS XR software does not support directly attached radio or atomic clocks. The master command should be used only when there is a temporary disruption in a reliable time service. It should not be employed as an alternative source by itself in the absence of a real-time service.
If the system has the master command configured and it cannot reach any clock that has a lower stratum number, the system claims to be synchronized at the configured stratum number. Other systems synchronize with it through NTP.
Note
The system clock must have been manually set from some source before the master command has an effect. This precaution protects against the distribution of erroneous time after the system is restarted.
Task ID
max-associations
To set the maximum number of Network Time Protocol (NTP) associations, use the max-associations command in NTP configuration mode. To restore the default setting, use the no form of this command.
Syntax Description
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the max-associations command to specify the maximum number of associations for an NTP server.
Task ID
multicast client
To configure an NTP interface as an NTP multicast client, use the multicast client command in NTP interface configuration mode. To remove the NTP multicast client configuration from an interface, use the no form of this command.
Syntax Description
ip-address IPv4 or IPv6 IP address of the multicast group to join. The default is the IPv4 address 224.0.1.1.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the multicast client command to configure an NTP interface to receive multicast packets that are sent to an IPv4 or IPv6 multicast group IP address. If you do not specify an IP address, the interface is configured to receive multicast packets sent to the IPv4 multicast group address 224.0.1.1. You can configure multiple multicast groups on the same interface.
Task ID
Examples
The following example shows how to configure the router to receive NTP multicast packets to the multicast group address of 224.0.1.1 through 10-Gigabit Ethernet interface 0/1/1/0:
RP/0/0/CPU0:router(config)# ntp interface TenGigE 0/1/1/0 RP/0/0/CPU0:router(config-ntp-int)# multicast clientmulticast destination
To configure an NTP interface as an NTP multicast server, use the multicast destination command in NTP interface configuration mode. To remove the NTP multicast server configuration from an interface, use the no form of this command.
multicast destination ip-address [ key key-id ] [ ttl ttl ] [ version number ]
no multicast destination ip-address [ key key-id ] [ ttl ttl ] [ version number ]
Syntax Description
ip-address The IPv4 or IPv6 multicast group IP address to which to send NTP multicast packets.
key key-id (Optional) Specifies an authentication key, where the value of the key-id argument is the authentication key to use when sending multicast packets to the specified multicast group.
ttl ttl (Optional) Specifies the time to live (TTL) of a multicast packet.
version number (Optional) Specifies the NTP version number.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Task ID
Examples
The following example shows how to configure the router to send NTP multicast packets to the multicast group address of 224.0.1.1 through 10-Gigabit Ethernet interface 0/1/1/0:
RP/0/0/CPU0:router(config)# ntp interface TenGigE 0/1/1/0 RP/0/0/CPU0:router(config-ntp-int)# multicast destination 224.0.1.1ntp
To enter Network Time Protocol (NTP) configuration mode and run NTP configuration commands, use the ntp command in global configuration mode.
Syntax Description
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
Support was added for the vrf vrf-name ip-address keyword and arguments.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
NTP configuration commands can also be run from global configuration mode by preceding the command string with the keyword. From NTP configuration mode, the following NTP configuration commands are available:
RP/0/0/CPU0:router(config-ntp)# ? access-group Control NTP access authenticate Authenticate time sources authentication-key Authentication key for trusted time sources broadcastdelay Estimated round-trip delay commit Commit the configuration changes to running default Set a command to its defaults describe Describe a command without taking real actions do Run an exec command exit Exit from this submode interface Configure NTP on an interface master Act as NTP master clock max-associations Set maximum number of associations no Negate a command or set its defaults peer Configure NTP peer port Enable NTP port server Configure NTP server show Show contents of configuration source Configure interface for source address trusted-key Key numbers for trusted time sources update-calendar Periodically update calendar with NTP timeUse the command with the vrf vrf-name keyword and argument to enter an NTP configuration mode specific to the specified VRF.
Task ID
Examples
The following example shows how to enter NTP configuration mode:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)#The following example shows how to enter an NTP configuration mode for a VRF called VRF1:
RP/0/0/CPU0:router(config)# ntp vrf vrf1 RP/0/0/CPU0:router(config-ntp-vrf)#ntp clear
To clear all Network Time Protocol (NTP) peers or a specific NTP peer, use the ntp clear command in EXEC mode.
Syntax Description
peer IPv4 address or hostname of the NTP peer to be cleared.
all Clears all NTP peers.
vrf vrf-name Clears a peer on the specified nondefault VRF.
ip-address IPv4 or IPv6 IP address of the peer.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
The * keyword was replaced by the all keyword.
Support was added for the vrf vrf-name ip-address keyword and arguments.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Task ID
ntp reset drift
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the ntp reset drift command to set the loopfilter state to NSET (never set) and reset the drift. Resetting the loopfilter state and drift enables the router to relearn the frequency of the NTP server clock. This is necessary if there is a synchronization error caused by a large frequency error. This can arise, for example, if the router switches from synchronizing with one NTP server to synchronizing with another NTP server with a different frequency.
Task ID
Examples
The following example shows how to reset the NTP drift and loopfilter state:
RP/0/0/CPU0:router# ntp reset drift Thu Nov 13 11:21:04.381 JSTThe following example shows NTP status before and after resetting NTP drift and loopfilter state:
RP/0/0/CPU0:router# show ntp status Thu Nov 13 11:20:53.122 JST Clock is synchronized, stratum 3, reference is 192.168.128.5 nominal freq is 1000.0000 Hz, actual freq is 1000.2787 Hz, precision is 2**24 reference time is CCC60CBE.9F836478 (11:17:34.623 JST Thu Nov 13 2008) clock offset is -3.172 msec, root delay is 189.289 msec root dispersion is 70.03 msec, peer dispersion is 0.11 msec loopfilter state is 'CTRL' (Normal Controlled Loop), drift is -0.0002785891 s/s system poll interval is 128, last update was 199 sec ago RP/0/0/CPU0:router# ntp reset drift Thu Nov 13 11:21:04.381 JST RP/0/0/CPU0:router# show ntp status Thu Nov 13 11:21:10.595 JST Clock is unsynchronized, stratum 16, no reference clock nominal freq is 1000.0000 Hz, actual freq is 1000.0000 Hz, precision is 2**24 reference time is CCC60CBE.9F836478 (11:17:34.623 JST Thu Nov 13 2008) clock offset is -3.172 msec, root delay is 0.000 msec root dispersion is 0.09 msec, peer dispersion is 0.00 msec loopfilter state is 'NSET' (Never set), drift is 0.0000000000 s/s system poll interval is 64, last update was 216 sec agopeer (NTP)
To configure the system clock to synchronize a peer or to be synchronized by a peer, use the peer command in one of the NTP configuration modes. To remove the peer command from the configuration file and restore the system to its default condition with respect to the command, use the no form of this command.
peer [ vrf vrf-name ] [ ipv4 | ipv6 ] ip-address [ version number ] [ key key-id ] [ minpoll interval ] [ maxpoll interval ] [ source type interface-path-id ] [prefer] [burst] [iburst]
no peer [ vrf vrf-name ] [ ipv4 | ipv6 ] ip-address
Syntax Description
vrf vrf-name (Optional) Applies the peer configuration to the specified nondefault VRF.
ipv4 (Optional) Specifies an IPv4 IP address.
ipv6 (Optional) Specifies an IPv6 IP address.
ip-address IPv4 or IPv6 address of the peer providing or being provided with the clock synchronization.
version number (Optional) Defines the Network Time Protocol (NTP) version number, where the number argument is a value from 1 to 4. The default is 4.
key key-id (Optional) Defines the authentication key, where the key-id argument is the authentication key to use when packets are sent to this peer. The authentication key is also used for packets received from the peer. By default, no authentication key is used.
minpoll interval (Optional) Defines the shortest polling interval, where the interval argument is specified in powers of two seconds. Range is from 4 to 17. The default value is 6.
maxpoll interval (Optional) Defines the longest polling interval, where the interval argument is specified in powers of two seconds. Range is from 4 to 17. The default value is 10.
source (Optional) IP source address. The default is the outgoing interface.
type (Optional) Interface type. For more information, use the question mark (?) online help function.
interface-path-id (Optional) Physical interface or virtual interface.
Note Use the show interfaces command to see a list of all interfaces currently configured on the router.
For more information about the syntax for the router, use the question mark (?) online help function.
prefer (Optional) Makes this peer the preferred peer that provides synchronization.
burst (Optional) Sends a series of packets instead of a single packet within each synchronization interval to achieve faster synchronization.
iburst (Optional) Sends a series of packets instead of a single packet within the initial synchronization interval to achieve faster initial synchronization.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the peer command to allow this machine to synchronize with the peer, or conversely.
Caution
Although using the prefer keyword can help reduce the switching among peers, you should avoid using the keyword because it interferes with the source selection mechanism of NTP and can result in a degradation in performance.
The value for the minpoll keyword must be less than or equal to the value for the maxpoll keyword. If this is not the case, the system issues an error message.
To provide peer-level service (as opposed to client/server-level service), it may be necessary to explicitly specify the NTP version for the peer if it is not version 4.
If you use the peer command in a VRF-specific NTP configuration mode, the command is applied to the specific VRF. If you are not in a VRF-specific NTP configuration mode, the command is applied to the default VRF unless you use the vrf vrf-name keyword and argument to specify a VRF.
Note
To change the configuration of a specific IP address from peer to server or from server to peer, use the no form of the peer or server command to remove the current configuration before you perform the new configuration. If you do not remove the old configuration before performing the new configuration, the new configuration does not overwrite the old configuration.
Task ID
Examples
The following example shows how to configure a networking device to allow its system clock to be synchronized with the clock of the peer (or conversely) at IP address 10.0.0.0 using NTP. The source IP address is the address of Packet-over-SONET/SDH (POS) interface 0/0/0/1.
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# peer 10.0.0.0 minpoll 8 maxpoll 12 source POS 0/0/0/1server (NTP)
To allow the system clock to be synchronized by a time server, use the server command in one of the NTP configuration modes. To remove the server command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
server [ vrf vrf-name ] [ ipv4 | ipv6 ] ip-address [ version number ] [ key key-id ] [ minpoll interval ] [ maxpoll interval ] [ source type interface-path-id ] [prefer] [burst] [iburst]
no server [ vrf vrf-name ] [ ipv4 | ipv6 ] ip-address
Syntax Description
vrf vrf-name (Optional) Applies the server configuration to the specified nondefault VRF.
ipv4 (Optional) Specifies an IPv4 IP address.
ipv6 (Optional) Specifies an IPv6 IP address.
ip-address IPv4 or IPv6 address of the time server providing the clock synchronization.
version number (Optional) Defines the Network Time Protocol (NTP) version number, where the number argument is a value from 1 to 4. The default is 4.
key key-id (Optional) Defines the authentication key, where the key-id argument is the authentication key to use when packets are sent to this peer. By default, no authentication key is used.
minpoll interval (Optional) Defines the shortest polling interval, where the interval argument is specified in powers of two seconds. Range is from 4 to 17. The default value is 6.
maxpoll interval (Optional) Defines the longest polling interval, where the interval argument is specified in powers of two seconds. Range is from 4 to 17. The default value is 10.
source (Optional) Specifies the IP source address. The default is the outgoing interface.
type (Optional) Interface type. For more information, use the question mark ( ? ) online help function.
interface-path-id (Optional) Physical interface or virtual interface.
Note Use the show interfaces command to see a list of all interfaces currently configured on the router.
For more information about the syntax for the router, use the question mark (?) online help function.
prefer (Optional) Makes this peer the preferred server that provides synchronization.
burst (Optional) Sends a series of packets instead of a single packet within each synchronization interval to achieve faster synchronization.
iburst (Optional) Sends a series of packets instead of a single packet within the initial synchronization interval to achieve faster initial synchronization.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
The value for the minpoll keyword must be less than or equal to the value for the maxpoll keyword. If this is not the case, the system issues an error message.
Using the prefer keyword reduces switching back and forth among servers.
If you use the server command in a VRF-specific NTP configuration mode, the command is applied to the specific VRF. If you are not in a VRF-specific NTP configuration mode, the command is applied to the default VRF unless you use the vrf vrf-name keyword and argument to specify a VRF.
Note
To change the configuration of a specific IP address from peer to server or from server to peer, use the no form of the peer or server command to remove the current configuration before you perform the new configuration. If you do not remove the old configuration before performing the new configuration, the new configuration does not overwrite the old configuration.
Task ID
Examples
The following example shows how to configure a router to allow its system clock to be synchronized with the clock of the peer at IP address 209.165.201.1 using NTP:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# server 209.165.201.1 minpoll 8 maxpoll 12show calendar
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the command to display the time and date in Coordinated Universal Time (UTC) format.
Task ID
show ntp associations
To display the status of Network Time Protocol (NTP) associations, use the show ntp associations command in privileged EXEC mode.
Syntax Description
detail (Optional) Displays detailed information about each NTP association.
location node-id (Optional) Displays the status of NTP associations from the designated node. The node-id argument is entered in the rack/slot/module notation.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
The output was modified to display nondefault VRF instances and to accommodate IPv6 addresses.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Output for the command is displayed only if NTP is configured on the router.
Task ID
Examples
The following example shows sample output from the command:
RP/0/0/CPU0:router# show ntp associations Wed Jul 30 04:03:13.471 PST DST address ref clock st when poll reach delay offset disp ~172.19.69.1 172.24.114.33 3 25 64 3 2.89 57550122 39377 ~2001:db8::feed .INIT. 16 - 64 0 0.00 0.000 15937 ~2001:db8::beef vrf vrf_1 .INIT. 16 - 64 0 0.00 0.000 16000 * sys_peer, # selected, + candidate, - outlayer, x falseticker, ~ configureddescribes the significant fields shown in the display.
Table 1 show ntp associations Field Descriptions Field
Description
*
Peer has been declared the system peer and lends its variables to the system variables.
# Peer is a survivor, but not among the first six peers sorted by synchronization distance. If the association is ephemeral, it may be demobilized to conserve resources.
+
Peer is a survivor and a candidate for the combining algorithm.
-
Peer is discarded by the clustering algorithm as an outlier.
x
Peer is discarded by the intersection algorithm as a falseticker.
~
Indicates peer is statically configured.
address
IPv4 or IPv6 address of the peer. If a nondefault VRF is configured for the peer, the VRF follows the address.
ref clock
Reference clock type or address for the peer.
st
Stratum setting for the peer.
when
Time since last NTP packet was received from peer, in milliseconds.
poll
Polling interval, in seconds.
reach
Peer reachability (bit string, in octal).
delay
Round-trip delay to peer, in milliseconds.
offset
Relative time difference between a peer clock and a local clock, in milliseconds.
disp
Dispersion.
The following example shows sample output from the command with the detail keyword:
RP/0/0/CPU0:router# show ntp associations detail 172.19.69.1 configured, our_master, sane, valid, stratum 2 ref ID 171.68.10.150, time C4143AAE.00FCF396 (18:27:58.003 UTC Tue Mar 30 2004) our mode client, peer mode server, our poll intvl 64, peer poll intvl 64 root delay 5.23 msec, root disp 4.07, reach 3, sync dist 0.0077 delay 1.9829 msec, offset -3.7899 msec, dispersion 0.0358 precision 2**18, version 4 org time C4143B8D.7EBD5FEF (18:31:41.495 UTC Tue Mar 30 2004) rcv time C4143B8D.801DFA44 (18:31:41.500 UTC Tue Mar 30 2004) xmt time C4143B8D.7F595E44 (18:31:41.497 UTC Tue Mar 30 2004) filtdelay = 2.99 1.98 1.98 1.99 1.99 1.99 2.98 1.98 filtoffset = -3.89 -3.74 -3.78 -3.81 -3.76 -3.73 -4.08 -3.64 filterror = 0.00 0.02 0.03 0.05 0.06 0.08 0.09 0.32 2001:0DB8::FEED vrf xxx configured, candidate, sane, valid, stratum 2 ref ID 64.103.34.14, time CB0C8C66.38285D84 (14:00:22.219 JST Fri Dec 14 2007) our mode client, peer mode server, our poll intvl 64, peer poll intvl 64 root delay 181.17 msec, root disp 3.19, reach 377, sync dist 0.1463 delay 104.9158 msec, offset -15.4552 msec, dispersion 0.0439 precision 2**16, version 4 org time CB0C8D0A.70282853 (14:03:06.438 JST Fri Dec 14 2007) rcv time CB0C8D0A.81CA0E2B (14:03:06.506 JST Fri Dec 14 2007) xmt time CB0C8D0A.66AAB677 (14:03:06.401 JST Fri Dec 14 2007) filtdelay = 105.90 104.92 104.91 104.91 105.90 105.85 105.90 104.91 filtoffset = -15.92 -15.67 -15.54 -15.59 -15.58 -15.54 -15.41 -14.36 filterror = 0.02 0.03 0.05 0.06 0.08 0.09 0.11 1.05 2001:0DB8::BEEF vrf yyy configured, our_master, sane, valid, stratum 2 ref ID 64.104.193.12, time CB0C8CC1.2C14CED1 (14:01:53.172 JST Fri Dec 14 2007) our mode client, peer mode server, our poll intvl 64, peer poll intvl 64 root delay 160.83 msec, root disp 4.35, reach 377, sync dist 0.1372 delay 104.9302 msec, offset -14.6327 msec, dispersion 0.0183 precision 2**18, version 4 org time CB0C8CCB.684619D8 (14:02:03.407 JST Fri Dec 14 2007) rcv time CB0C8CCB.79782B09 (14:02:03.474 JST Fri Dec 14 2007) xmt time CB0C8CCB.5E9A5429 (14:02:03.369 JST Fri Dec 14 2007) filtdelay = 104.93 104.93 104.93 104.93 104.93 104.93 104.93 104.93 filtoffset = -14.71 -14.53 -14.78 -14.73 -14.70 -14.52 -14.59 -14.50 filterror = 0.00 0.02 0.03 0.05 0.06 0.08 0.09 0.11describes the significant fields shown in the display.
Table 2 show ntp associations detail Field Descriptions Field
Descriptions
vrf
Nondefault VRF, if specified for this peer.
configured
Statically configured peer.
dynamic
Dynamically discovered peer.
our_master
Synchronization of the local machine to this peer.
sane
Passing of basic sanity checks by this peer.
ref ID
Address of machine to which the peer is synchronized.
time
Last time stamp that the peer received from its master.
our mode
Mode relative to peer (active/passive/client/server/bdcast/bdcast client).
peer mode
Mode of peer relative.
our poll intvl
Poll interval to peer.
peer poll intvl
Poll interval of interval.
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 this clock.
dispersion
Dispersion of peer clock.
precision
Precision of peer clock in (Hertz) Hz.
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 of each sample, in milliseconds.
filtoffset
Clock offset of each sample, in milliseconds.
filterror
Approximate error of each sample.
show ntp status
Syntax Description
location node-id (Optional) Displays the status of NTP from the designated node. The node-id argument is entered in the rack/slot/module notation.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
The output was modified to display nondefault VRF instances and IPv6 addresses.
The loopfilter state, drift, system poll interval, and last update display fields were added to the output.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Task ID
Examples
The following example shows sample output from the command:
RP/0/0/CPU0:router# show ntp status Clock is synchronized, stratum 3, reference is 192.168.128.5 nominal freq is 1000.0000 Hz, actual freq is 1000.0021 Hz, precision is 2**24 reference time is CC38EC6A.8FCCA1C4 (10:10:02.561 JST Tue Jul 29 2008) clock offset is -124.051 msec, root delay is 174.060 msec root dispersion is 172.37 msec, peer dispersion is 0.10 msec loopfilter state is 'CTRL' (Normal Controlled Loop), drift is -0.0000021106 s/s system poll interval is 32, last update was 19 sec agodescribes the significant fields shown in the display.
Table 3 show ntp status Field Descriptions Field
Description
synchronized
Synchronized system to an NTP peer.
stratum
NTP stratum of this system.
reference
IPv4 address or first 32 bits of the MD5 hash of the IPv6 address of the peer to which clock is synchronized.
vrf
VRF through which the peer routes.
nominal freq
Nominal frequency in Hertz (Hz) of the system hardware clock.
actual freq
Measured frequency in Hz of the system hardware clock.
precision
Precision of the clock of this system in Hz.
reference time
Reference time stamp.
clock offset
Offset of clock to synchronized peer, in milliseconds.
root delay
Total delay along path to root clock, in milliseconds.
root dispersion
Dispersion of root path.
peer dispersion
Dispersion of synchronized peer.
loopfilter state
The state of the clock state machine transition function.
drift
Drift of the hardware clock.
system poll interval
Poll interval of the peer.
last update
Time the router last updated its NTP information.
source (NTP)
To use a particular source address in Network Time Protocol (NTP) packets, use the source command in one of the NTP configuration modes. To remove the command from the configuration file and restore the system to its default condition, use the no form of this command.
Syntax Description
vrf vrf-name (Optional) Applies the source address configuration to the specified nondefault VRF.
type (Optional) Interface type. For more information, use the question mark (?) online help function.
interface-path-id (Optional) Physical interface or virtual interface.
Note Use the show interfaces command to see a list of all interfaces currently configured on the router.
For more information about the syntax for the router, use the question mark ( ? ) online help function.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
Support was added for the vrf vrf-name keyword and argument.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the command 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 has been configured with the server (NTP) or peer (NTP) command, that value overrides the global value.
Use the command in a VRF-specific NTP configuration mode or use the vrf vrf-name keyword and argument to configure the source address for a specific nondefault VRF. Otherwise, the configuration is applied to the default VRF.
Task ID
Examples
The following example shows how to configure the router to use the IP address of Packet-over-SONET/SDH (POS) interface 0/0/0/1 as the source address of all outgoing NTP packets:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# source POS 0/0/0/1trusted-key
To designate a Network Time Protocol (NTP) trusted key, use the trusted-key command in NTP configuration mode. To remove the command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
Syntax Description
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
If authentication is enabled, use the command to define one or more key numbers (corresponding to the keys defined with the authentication-key [NTP] command) that a NTP system must provide in its NTP packets for this system to synchronize to it. Because the other system must know the correct authentication key, this precaution provides protection against accidentally synchronizing the system to a system that is not trusted.
Task ID
Examples
The following example shows how to configure the system to synchronize only to systems providing authentication key 42 in its NTP packets:
RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# authenticate RP/0/0/CPU0:router(config-ntp)# authentication-key 42 md5 clear key1 RP/0/0/CPU0:router(config-ntp)# trusted-key 42update-calendar
To update the calendar periodically from Network Time Protocol (NTP), use the update-calendar command in NTP configuration mode. To remove the command from the configuration file and restore the system to its default condition with respect to the command, use the no form of this command.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.3.0
No modification.
Release 3.4.0
No modification.
Release 3.5.0
No modification.
Release 3.6.0
No modification.
Release 3.7.0
No modification.
Release 3.8.0
No modification.
Release 3.9.0
No modification.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Your router has a calendar that is separate from the software clock. This calendar runs continuously, even if the router is powered off or rebooted.
If a router is synchronized to an outside time source through NTP, it is a good idea to update the router’s calendar with the time learned from NTP. Otherwise, the calendar may gradually lose or gain time.
After you configure the command, NTP updates the calendar with the software clock every hour.
Task ID
