Cisco IOS IPv6 Command Reference

snmp-server user

To configure a new user to a Simple Network Management Protocol (SNMP) group, use the snmp-server user command in global configuration mode. To remove a user from an SNMP group, use the no form of this command.

snmp-server user username group-name [remote host [udp-port port] [vrf vrf-name]] {v1 | v2c | v3 [encrypted] [auth {md5 | sha} auth-password]} [access [ipv6 nacl] [priv {des | 3des | aes {128 | 192 |256}} privpassword] {acl-number | acl-name}]

no snmp-server user username group-name [remote host [udp-port port] [vrf vrf-name]] {v1 | v2c | v3 [encrypted] [auth {md5 | sha} auth-password]} [access [ipv6 nacl] [priv {des | 3des | aes {128 | 192 |256}} privpassword] {acl-number | acl-name}]

Syntax Description

Command Default

See Table 327 in the "Usage Guidelines" section for default behaviors for encryption, passwords, and access lists.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

To configure a remote user, specify the IP address or port number for the remote SNMP agent of the device where the user resides. Also, before you configure remote users for a particular agent, configure the SNMP engine ID, using the snmp-server engineID command with the remote keyword. The remote agent's SNMP engine ID is needed when computing the authentication and privacy digests from the password. If the remote engine ID is not configured first, the configuration command will fail.

For the privpassword and auth-password arguments, the minimum length is one character; the recommended length is at least eight characters, and should include both letters and numbers.

Table 327 describes the default user characteristics for encryption, passwords, and access lists.

SNMP passwords are localized using the SNMP engine ID of the authoritative SNMP engine. For informs, the authoritative SNMP agent is the remote agent. You need to configure the remote agent's SNMP engine ID in the SNMP database before you can send proxy requests or informs to it.

Note Changing the engine ID after configuring the SNMP user, does not allow to remove the user. To remove the user, you need to first reconfigure the SNMP user.

Working with Passwords and Digests

No default values exist for authentication or privacy algorithms when you configure the command. Also, no default passwords exist. The minimum length for a password is one character, although Cisco recommends using at least eight characters for security. If you forget a password, you cannot recover it and will need to reconfigure the user. You can specify either a plain-text password or a localized MD5 digest.

If you have the localized MD5 or Secure Hash Algorithm (SHA) digest, you can specify that string instead of the plain-text password. The digest should be formatted as aa:bb:cc:dd where aa, bb, and cc are hexadecimal values. Also, the digest should be exactly 16 octets long.

Examples

The following example shows how to add the user abcd to the SNMP server group named public. In this example, no access list is specified for the user, so the standard named access list applied to the group applies to the user.

Router(config)# snmp-server user abcd public v2c 

The following example shows how to add the user abcd to the SNMP server group named public. In this example, access rules from the standard named access list qrst apply to the user.

Router(config)# snmp-server user abcd public v2c access qrst 

In the following example, the plain-text password cisco123 is configured for the user abcd in the SNMP server group named public:

Router(config)# snmp-server user abcd public v3 auth md5 cisco123 

When you enter a show running-config command, a line for this user will be displayed. To learn if this user has been added to the configuration, use the show snmp user command.

Note The show running-config command does not display any of the active SNMP users created in authPriv or authNoPriv mode, though it does display the users created in noAuthNoPriv mode. To display any active SNMPv3 users created in authPriv, authNoPrv, or noAuthNoPriv mode, use the show snmp user command.

If you have the localized MD5 or SHA digest, you can specify that string instead of the plain-text password. The digest should be formatted as aa:bb:cc:dd where aa, bb, and cc are hexadecimal values. Also, the digest should be exactly 16 octets long.

In the following example, the MD5 digest string is used instead of the plain-text password:

Router(config)# snmp-server user abcd public v3 encrypted auth md5 
00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF

In the following example, the user abcd is removed from the SNMP server group named public:

Router(config)# no snmp-server user abcd public v2c 

In the following example, the user abcd from the SNMP server group named public specifies the use of the 168-bit 3DES algorithm for privacy encryption with secure3des as the password.

Router(config)# snmp-server user abcd public priv v2c 3des secure3des

Related Commands

snmp trap link-status

To enable Simple Network Management Protocol (SNMP) link trap generation, use the snmp trap link-status command in either interface configuration mode or service instance configuration mode. To disable SNMP link traps, use the no form of this command.

snmp trap link-status [permit duplicates]

no snmp trap link-status [permit duplicates]

Syntax Description

.

Command Default

SNMP link traps are sent when an interface goes up or down.

Command Modes

Interface configuration (config-if)
Service instance configuration (config-if-srv)

Command History

Usage Guidelines

By default, SNMP link traps are sent when an interface goes up or down. For interfaces expected to go up and down during normal usage, such as ISDN interfaces, the output generated by these traps may not be useful. The no form of this command disables these traps.

The permit and duplicates keywords are used together and cannot be used individually. Use the permit duplicates keyword pair when an interface is not generating SNMP linkup traps, linkdown traps, or both. When the snmp trap link-status permit duplicates command is configured, more than one trap may be sent for the same linkup or linkdown transition.

The permit duplicates keyword pair does not guarantee that SNMP link traps will be generated nor should configuring these keywords be required to receive traps.

By default, in service instance configuration mode SNMP link traps are not sent. Also, the permit duplicates keyword pair is not available in service instance configuration mode.

Cisco 10000 Series Router Usage Guidelines

In Cisco IOS Release 12.2(33)SB, the virtual-template snmp command has a new default configuration. Instead of being enabled by default, no virtual-template snmp is the default configuration. This setting enhances scaling and prevents large numbers of entries in the MIB ifTable, thereby avoiding CPU Hog messages as SNMP uses the interfaces MIB and other related MIBs.

If you configure the no virtual-template snmp command, the router no longer accepts the snmp trap link-status command under a virtual-template interface. Instead, the router displays a configuration error message such as the following:

Router(config)# interface virtual-template 1

Router(config-if)# snmp trap link-status

%Unable set link-status enable/disable for interface

If your configuration already has the snmp trap link-status command configured under a virtual-template interface and you upgrade to Cisco IOS Release 12.2(33)SB, the configuration error occurs when the router reloads even though the virtual template interface is already registered in the interfaces MIB.

Examples

The following example shows how to disable SNMP link traps related to the ISDN BRI 0 interface:

Router(config)# interface bri 0

Router(config-if)# no snmp trap link-status

The following example shows how to enable SNMP link traps for service instance 50 on Ethernet interface 0/1:

Router(config)# interface ethernet 0/1

Router(config-if)# service instance 50 ethernet

Router(config-if-srv)# snmp trap link-status

Router(config-if-srv)# exit

Related Commands

sntp address

To specify the IPv6 Simple Network Time Protocol (SNTP) server address list to be sent to the client, use the sntp address command in DHCP for IPv6 pool configuration mode. To remove the SNTP server address list, use the no form of the command.

sntp address ipv6-address

no sntp address ipv6-address

Syntax Description

Command Default

No SNTP server address is specified.

Command Modes

IPv6 DHCP pool configuration

Command History

Usage Guidelines

The Dynamic Host Configuration Protocol (DHCP) for IPv6 for stateless configuration allows a DHCP for IPv6 client to export configuration parameters (that is, DHCP for IPv6 options) to a local DHCP for IPv6 server pool. The local DHCP for IPv6 server can then provide the imported configuration parameters to other DHCP for IPv6 clients.

The SNTP server address list option provides a list of one or more IPv6 addresses of SNTP servers available to the client for synchronization. The clients use these SNTP servers to synchronize their system time to that of the standard time servers.

Clients must treat the list of SNTP servers as an ordered list, and the server may list the SNTP servers in decreasing order of preference. The option defined in this document can be used only to configure information about SNTP servers that can be reached using IPv6.

The SNTP server option code is 31. For more information on DHCP options and suboptions, see the "DHCP Options" appendix in the Network Registrar User's Guide, Release 6.2.

Examples

The following example shows how to specify the SNTP server address:

sntp address 300::1

Related Commands

spd extended-headroom

To configure Selective Packet Discard (SPD) extended headroom, use the spd extended-headroom command in global configuration mode. To return to the default value, use the no form of this command.

spd extended-headroom size

no spd extended-headroom

Syntax Description

Command Default

The SPD extended headroom default is 10 packets.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

Because Interior Gateway Protocols (IGPs) and link stability are tenuous and crucial, such packets are given the highest priority and are given extended SPD headroom with a default of 10 packets. These packets are not dropped if the size of the input hold queue is lower than 185 (input queue default size + SPD headroom size + SPD extended headroom).

Examples

The following example shows how to configure SPD extended headroom to be 11 packets:

Router(config)# spd extended-headroom 11

Related Commands

spd headroom

To configure Selective Packet Discard (SPD) headroom, use the spd headroom command in global configuration mode. To return to the default value, use the no form of this command.

spd headroom size

no spd headroom

Syntax Description

Command Default

The SPD headroom default is 100 packets.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

SPD prioritizes IPv6 packets with a precedence of 7 by allowing the software to queue them into the process level input queue above the normal input queue limit. The number of packets allowed in excess of the normal limit is called the SPD headroom, the default being 100, which means that a high precedence packet is not dropped if the size of the input hold queue is lower than 175 (input queue default size + SPD headroom size).

Examples

The following example shows how to configure SPD headroom to be 95 packets:

Router(config)# spd headroom 95

Related Commands

spf-interval (IPv6)

To configure how often Cisco IOS software performs the shortest path first (SPF) calculation, use the spf-interval command in address family configuration mode. To restore the default interval, use the no form of this command.

spf-interval [level-1 | level-2] seconds [initial-wait] [secondary-wait]

no spf-interval seconds

Syntax Description

Command Default

The default is 5 seconds.

Command Modes

Address family configuration

Command History

Usage Guidelines

SPF calculations are performed only when the topology changes. They are not performed when external routes change.

The spf-interval (IPv6) command controls how often Cisco IOS software can perform the SPF calculation. The SPF calculation is processor-intensive. Therefore, it may be useful to limit how often the SPF calculation is performed, especially when the area is large and the topology changes often. Increasing the SPF interval reduces the processor load of the router, but it could slow down the rate of convergence.

If IPv6 and IPv4 are configured on the same interface, they must be running the same Intermediate System-to-Intermediate System (IS-IS) level.

You can use the spf-interval (IPv6) command only when using the IS-IS multitopology support for IPv6 feature.

Examples

The following example sets the SPF calculation interval to 30 seconds:

Router(config)# router isis

Router(config-router)# address-family ipv6

Router(config-router-af)# spf-interval 30

Related Commands

split-horizon (IPv6 RIP)

To configure split horizon processing of IPv6 Routing Information Protocol (RIP) router updates, use the split-horizon command in router configuration mode. To disable the split horizon processing of IPv6 RIP updates, use the no form of this command.

split-horizon

no split-horizon

Syntax Description

This command has no arguments or keywords.

Command Default

Split horizon is configured and active by default. However, for ATM interfaces and subinterfaces split-horizon is disabled by default.

Command Modes

Router configuration

Command History

Usage Guidelines

The split-horizon (IPv6 RIP) command is similar to the ip split-horizon command, except that it is IPv6-specific.

This command configures split horizon processing of IPv6 RIP router updates. When split horizon is configured, the advertisement of networks out the interfaces from which the networks are learned is suppressed.

If both split horizon and poison reverse are configured, then split horizon behavior is replaced by poison reverse behavior (routes learned via RIP are advertised out the interface over which they were learned, but with an unreachable metric).

Note In general, changing the state of the default for the split-horizon command is not recommended, unless you are certain that your application requires a change in order to properly advertise routes. If split horizon is disabled on a serial interface (and that interface is attached to a packet-switched network), you must disable split horizon for all routers and access servers in any relevant multicast groups on that network.

Examples

The following example configures split horizon processing for the IPv6 RIP routing process named cisco:

Router(config)# ipv6 router rip cisco

Router(config-rtr)# split-horizon

Related Commands

ssh

To start an encrypted session with a remote networking device, use the ssh command in privileged EXEC or user EXEC mode.

ssh [-v {1 | 2}] [-c {3des | aes128-cbc | aes192-cbc | aes256-cbc}] [-l userid | -l userid:vrfname number ip-address | -l userid:rotarynumber ip-address] [-m {hmac-md5 | hmac-md5-96 | hmac-sha1 | hmac-sha1-96}] [-o numberofpasswordprompts n] [-p port-num] {ip-addr | hostname} [command] [-vrf]

Syntax Description

Command Default

No encrypted session exists if the command is not used.

Command Modes

User EXEC (>)
Privileged EXEC (#)

Command History

Usage Guidelines

The ssh command enables a Cisco router to make a secure, encrypted connection to another Cisco router or device running an SSH Version 1 or Version 2 server. This connection provides functionality that is similar to that of an outbound Telnet connection except that the connection is encrypted. With authentication and encryption, the SSH client allows for a secure communication over an insecure network.

Note•SSH Version 1 is supported on DES (56-bit) and 3DES (168-bit) data encryption software images only. In DES software images, DES is the only encryption algorithm available. In 3DES software images, both DES and 3DES encryption algorithms are available.

•SSH Version 2 supports only the following crypto algorithms: aes128-cbc, aes192-cbc, and aes256-cbc. SSH Version 2 is supported only in 3DES images.

•SSH Version 1 does not support HMAC algorithms.

The following example illustrates the initiation of a secure session between the local router and the remote host HQhost to run the show users command. The result of the show users command is a list of valid users who are logged in to HQhost. The remote host will prompt for the adminHQ password to authenticate the user adminHQ. If the authentication step is successful, the remote host will return the result of the show users command to the local router and will then close the session.

ssh -l adminHQ HQhost "show users"

The following example illustrates the initiation of a secure session between the local router and the edge router HQedge to run the show ip route command. In this example, the edge router prompts for the adminHQ password to authenticate the user. If the authentication step is successful, the edge router will return the result of the show ip route command to the local router.

ssh -l adminHQ HQedge "show ip route" 

The following example shows the SSH client using 3DES to initiate a secure remote command connection with the HQedge router. The SSH server running on HQedge authenticates the session for the admin7 user on the HQedge router using standard authentication methods. The HQedge router must have SSH enabled for authentication to work.

ssh -l admin7 -c 3des -o numberofpasswordprompts 5 HQedge

The following example shows a secure session between the local router and a remote IPv6 router with the address 3ffe:1111:2222:1044::72 to run the show running-config command. In this example, the remote IPv6 router prompts for the adminHQ password to authenticate the user. If the authentication step is successful, the remote IPv6 router will return the result of the show running-config command to the local router and will then close the session.

ssh -l adminHQ 3ffe:1111:2222:1044::72 "show running-config"

Note A hostname that maps to the IPv6 address 3ffe:1111:2222:1044::72 could have been used in the last example.

The following example shows a SSH Version 2 session using the crypto algorithm aes256-cbc and an HMAC of hmac-sha1-96. The user ID is user2, and the IP address is 10.76.82.24.

ssh -v 2 -c aes256-cbc -m hmac-sha1-96 -1 user2 10.76.82.24

The following example shows that reverse SSH has been configured on the SSH client:

ssh -l lab:1 router.example.com

The following command shows that Reverse SSH will connect to the first free line in the rotary group:

ssh -l lab:rotary1 router.example.com

Related Commands

standby ipv6

To activate the Hot Standby Router Protocol (HSRP) in IPv6, use the standby ipv6 command in interface configuration mode. To disable HSRP, use the no form of this command.

standby [group-number] ipv6 {ipv6-global-address | ipv6-address/prefix-length | ipv6-prefix/prefix-length | link-local-address | autoconfig}

no standby [group-number] ipv6 {ipv6-global-address | ipv6-address/prefix-length | ipv6-prefix/prefix-length | link-local-address | autoconfig}

Syntax Description

Command Default

The default group number is 0.
HSRP is disabled by default.

Command Modes

Interface configuration

Command History

Usage Guidelines

An Ethernet or FDDI type interface must be used for HSRP for IPv6. HSRP version 2 must be enabled on an interface before HSRP IPv6 can be configured.

The standby ipv6 command enables an HSRP group for IPv6 operation. If the autoconfig keyword is used, then a link-local address will be generated from the link-local prefix and a modified EUI-64 format interface identifier, where the EUI-64 interface identifier is created from the relevant HSRP virtual MAC address.

If an IPv6 global address is used, it must include an IPv6 prefix length. If a link-local address is used, it does not have a prefix.

Examples

The following example enables an HSRP group for IPv6 operation:

Router(config)# standby version 2

Router(config)# interface ethernet 0

Router(config-if)# standby ipv6 autoconfig

The following example shows three HSRP global IPv6 addresses with an explicitly configured link-local address:

interface Ethernet0/0

 no ip address

 ipv6 address 2001::0DB8:1/64

 standby version 2

 standby 1 ipv6 FE80::1:CAFÉ 

 standby 1 ipv6 2001::0DB8:2/64

 standby 1 ipv6 2001:0DB8::3/64

 standby 1 ipv6 2001:0DB8::4/64 

Related Commands

standby preempt

To configure Hot Standby Router Protocol (HSRP) preemption and preemption delay, use the standby preempt command in interface configuration mode. To restore the default values, use the no form of this command.

standby [group-number] preempt [delay {minimum seconds | reload seconds | sync seconds}]

no standby [group-number] preempt [delay {minimum seconds | reload seconds | sync seconds}]

Syntax Description

Command Default

The default group number is 0.
The default delay is 0 seconds; if the router wants to preempt, it will do so immediately.
By default, the router that comes up later becomes the standby.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Note Cisco IOS 12.2SX software releases earlier than Cisco IOS Release 12.2(33)SXH use the syntax from Cisco IOS Release 12.1, which supports preempt as a keyword for the standby priority command. Cisco IOS Release 12.2(33)SXH and later releases use Cisco IOS Release 12.2 syntax, which requires standby preempt and standby priority to be entered as separate commands.

When the standby preempt command is configured, the router is configured to preempt, which means that when the local router has a Hot Standby priority higher than the current active router, the local router should attempt to assume control as the active router. If preemption is not configured, the local router assumes control as the active router only if it receives information indicating no router is in the active state (acting as the designated router).

This command is separate from the standby delay minimum reload interface configuration command, which delays HSRP groups from initializing for the specified time after the interface comes up.

When a router first comes up, it does not have a complete routing table. If it is configured to preempt, it will become the active router, yet it is unable to provide adequate routing services. Solve this problem by configuring a delay before the preempting router actually preempts the currently active router.

When group number 0 is used, no group number is written to NVRAM, providing backward compatibility.

IP redundancy clients can prevent preemption from taking place. The standby preempt delay sync seconds command specifies a maximum number of seconds to allow IP redundancy clients to prevent preemption. When this expires, then preemption takes place regardless of the state of the IP redundancy clients.

The standby preempt delay reload seconds command allows preemption to occur only after a router reloads. This provides stabilization of the router at startup. After this initial delay at startup, the operation returns to the default behavior.

The no standby preempt delay command will disable the preemption delay but preemption will remain enabled. The no standby preempt delay minimum seconds command will disable the minimum delay but leave any synchronization delay if it was configured.

When the standby follow command is used to configure an HSRP group to become an IP redundancy client of another HSRP group, the client group takes its state from the master group it is following. Therefore, the client group does not use its timer, priority, or preemption settings. A warning is displayed if these settings are configured on a client group:

Router(config-if)# standby 1 preempt delay minimum 300

    % Warning: This setting has no effect while following another group.

Examples

In the following example, the router will wait for 300 seconds (5 minutes) before attempting to become the active router:

Router(config)# interface ethernet 0

Router(config-if)# standby ip 172.19.108.254

Router(config-if)# standby preempt delay minimum 300 

standby priority

To configure Hot Standby Router Protocol (HSRP) priority, use the standby priority command in interface configuration mode. To restore the default values, use the no form of this command.

standby [group-number] priority priority

no standby [group-number] priority priority

Syntax Description

Command Default

The default group number is 0.
The default priority is 100.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Note Cisco IOS 12.2SX software releases earlier than Cisco IOS Release 12.2(33)SXH use the syntax from Cisco IOS Release 12.1, which supports preempt as a keyword for the standby priority command. Cisco IOS Release 12.2(33)SXH and later releases use Cisco IOS Release 12.2 syntax, which requires standby preempt and standby priority to be entered as separate commands.

When group number 0 is used, the number 0 is written to NVRAM, providing backward compatibility.

The assigned priority is used to help select the active and standby routers. Assuming that preemption is enabled, the router with the highest priority becomes the designated active router. In case of ties, the primary IP addresses are compared, and the higher IP address has priority.

Note that the priority of the device can change dynamically if an interface is configured with the standby track command and another interface on the router or a tracked object goes down.

When the standby follow command is used to configure an HSRP group to become an IP redundancy client of another HSRP group, the client group takes its state from the master group it is following. Therefore, the client group does not use its timer, priority, or preemption settings. A warning is displayed if these settings are configured on a client group:

Router(config-if)# standby 1 priority 110

%Warning: This setting has no effect while following another group.

Examples

In the following example, the router has a priority of 120 (higher than the default value):

Router(config)# interface ethernet 0

Router(config-if)# standby ip 172.19.108.254

Router(config-if)# standby priority 120 

Router(config-if)# standby preempt delay 300

Related Commands

standby version

To change the version of the Hot Standby Router Protocol (HSRP), use the standby version command in interface configuration mode. To change to the default version, use the no form of this command.

standby version {1 | 2}

no standby version

Syntax Description

Command Default

HSRP version 1 is the default HSRP version.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

HSRP version 2 addresses limitations of HSRP version 1 by providing an expanded group number range of 0 to 4095.

HSRP version 2 does not interoperate with HSRP version 1. An interface cannot operate both version 1 and version 2 because both versions are mutually exclusive. However, the different versions can be run on different physical interfaces of the same router. The group number range is from 0 to 255 for HSRP version 1 and from 0 to 4095 for HSRP version 2. You cannot change from version 2 to version 1 if you have configured groups above 255. Use the no standby version command to set the HSRP version to the default version, version 1.

If an HSRP version is changed, each group will reinitialize because it now has a new virtual MAC address.

Examples

The following example shows how to configure HSRP version 2 on an interface with a group number of 500:

Router(config)# interface vlan500

Router(config-if)# standby version 2

Router(config-if)# standby 500 ip 172.20.100.10 

Router(config-if)# standby 500 priority 110 

Router(config-if)# standby 500 preempt 

Router(config-if)# standby 500 timers 5 15

Related Commands

stub

Note Effective with Cisco IOS Release 15.0(1)M and 12.2(33)SRE, the stub command was replaced by the eigrp stub command. See the eigrp stub command for more information.

To configure a router as a stub using Enhanced Interior Gateway Routing Protocol (EIGRP), use the stub command in router configuration mode. To disable the EIGRP stub routing feature, use the no form of this command.

stub [receive-only | connected | static | summary | redistributed]

no stub [receive-only | connected | static | summary | redistributed]

Syntax Description

Command Default

Stub routing is not enabled.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

Use the stub command to configure a router as a stub where the router directs all IPv6 traffic to a distribution router.

The stub command can be modified with keywords, and more than one keyword can be used in the same syntax. These options can be used in any combination, except for the receive-only keyword. The receive-only keyword will restrict the router from sharing any of its routes with any other router in that EIGRP autonomous system, and the receive-only keyword will not permit any other option to be specified because it prevents any type of route from being sent. The connected, static, summary, and redistributed keywords can be used in any combination but cannot be used with the receive-only keyword.

If any of these four keywords is used with the stub command, only the route types specified by the particular keywords will be sent. Route types specified by the nonused keywords will not be sent.

The connected keyword permits the EIGRP stub routing feature to send connected routes. If the connected routes are not covered by a network statement, it may be necessary to redistribute connected routes with the redistribute connected command under the EIGRP process. This option is enabled by default.

The static keyword permits the EIGRP stub routing feature to send static routes. Without the configuration of this option, EIGRP will not send any static routes, including internal static routes that normally would be automatically redistributed. It will still be necessary to redistribute static routes with the redistribute static command.

The summary keyword permits the EIGRP stub routing feature to send summary routes. Summary routes can be created manually with the ipv6 summary address eigrp command or automatically at a major network border router with the auto-summary command enabled. This option is enabled by default.

The redistributed keyword permits the EIGRP stub routing feature to send other routing protocols and autonomous systems. Without the configuration of this option, EIGRP will not advertise redistributed routes.

Note Multiaccess interfaces such as ATM, Ethernet, Frame Relay, ISDN PRI, and X.25 are supported by the EIGRP stub routing feature only when all routers on that interface, except the hub, are configured as stub routers.

Examples

In the following example, the stub command is used to configure the router as a stub that advertises connected and summary routes:

ipv6 router eigrp 1

 network 3FEE:12E1:2AC1:EA32::/64

 stub

In the following example, the stub command is issued with the connected and static keywords to configure the router as a stub that advertises connected and static routes (sending summary routes will not be permitted):

ipv6 router eigrp 1

 network 3FEE:12E1:2AC1:EA32::/64

 stub connected static

In the following example, the stub command is issued with the receive-only keyword to configure the router as a receive-only neighbor (connected, summary, and static routes will not be sent):

ipv6 router eigrp 1

 network 3FEE:12E1:2AC1:EA32::/64 eigrp 

 stub receive-only

In the following example, the stub command is issued with the redistributed keyword to configure the router to advertise other protocols and autonomous systems:

ipv6 router eigrp 1

 network 3FEE:12E1:2AC1:EA32::/64 eigrp 

 stub redistributed

Related Commands

subject-name

To specify the subject name in the certificate request, use the subject-name command in ca-trustpoint configuration mode. To clear any subject name from the configuration, use the no form of this command.

subject-name [x.500-name]

no subject-name [x.500-name]

Syntax Description

Defaults

If the x-500-name argument is not specified, the fully qualified domain name (FQDN), which is the default subject name, will be used.

Command Modes

Ca-trustpoint configuration

Command History

Usage Guidelines

Before you can issue the subject-name command, you must enable the crypto ca trustpoint command, which declares the certification authority (CA) that your router should use and enters ca-trustpoint configuration mode.

The subject-name command is an attribute that can be set for autoenrollment; thus, issuing this command prevents you from being prompted for a subject name during enrollment.

Examples

The following example shows how to specify the subject name for the "frog" certificate:

crypto ca trustpoint frog

 enrollment url http://frog.phoobin.com/  

 subject-name OU=Spiral Dept., O=tiedye.com

 ip-address ethernet-0

 auto-enroll regenerate

 password revokme

Related Commands

summary-prefix (IPv6 IS-IS)

To create aggregate IPv6 prefixes for Intermediate System-to-Intermediate System (IS-IS), use the summary-prefix command in address family configuration mode. To restore the default, use the no form of this command.

summary-prefix ipv6-prefix/prefix-length {level-1 | level-1-2 | level-2}

no summary-prefix ipv6-prefix/prefix-length {level-1 | level-1-2 | level-2}

Syntax Description

Command Default

All redistributed routes are advertised individually.

Command Modes

Address family configuration

Command History

Usage Guidelines

Multiple groups of prefixes can be summarized for a given level. Routes learned from other routing protocols can also be summarized. The metric used to advertise the summary is the smallest metric of all the more specific routes. This command helps reduce the size of the routing updates generated by the router, resulting in smaller routing tables on neighbor routers.

This command also reduces the size of the link-state packets (LSPs) and thus the link-state database (LSDB). It also helps ensure stability because a summary advertisement is depending on many more specific routes. If one more specific route flaps, in most cases this flapping does not cause a flap of the summary advertisement.

The drawback of summary prefixes is that other routes might have less information with which to calculate the most optimal routing table for all individual destinations.

Note When IS-IS advertises a summary prefix, it automatically inserts the summary prefix into the IPv6 routing table but labels it as a "discard" route entry. Any packet that matches the entry will be discarded to prevent routing loops. When IS-IS stops advertising the summary prefix, the routing table entry is removed.

Examples

The following example redistributes Routing Information Protocol (RIP) routes into IS-IS. In
the RIP routing table, there are IPv6 routes for 3FFE:F000:0001:0000::/64, 3FFE:F000:0002:0000::/64, 3FFE:F000:0003:0000::/64, and so on. This example advertises only 3FFE:F000::/24 into IPv6
IS-IS Level 1.

Router(config)# router isis area01

Router(config-router)# address-family ipv6

Router(config-router-af)# redistribute rip level-1 metric 40

Router(config-router-af)# summary-prefix 3FFE:F000::/24 level-1

summary-prefix (OSPFv3)

To configure an IPv6 summary prefix in Open Shortest Path First version 3 (OSPFv3), use the summary-prefix command in OSPFv3 router configuration mode, IPv6 address family configuration mode, or IPv4 address family configuration mode. To restore the default, use the no form of this command.

summary-prefix prefix [not-advertise | tag tag-value]

no summary-prefix prefix [not-advertise | tag tag-value]

Syntax Description

Command Default

No IPv6 summary prefix is defined.

Command Modes

OSPFv3 router configuration mode (config-router)
IPv6 address family configuration (config-router-af)
IPv4 address family configuration (config-router-af)

Command History

Usage Guidelines

This command can be used to summarize routers redistributed from other routing protocols. Multiple groups of addresses can be summarized. The metric used to advertise the summary is the smallest metric of all the more specific routes. This command helps reduce the size of the routing table.

Examples

In the following example, tthe summary prefix FEC0::/24 includes addresses FEC0::/1 through FEC0::/24. Only the address FEC0::/24 is advertised in an external link-state advertisement.

summary-prefix FEC0::/24

Related Commands

switchport

Cisco 3550, 4000, and 4500 Series Switches

To put an interface that is in Layer 3 mode into Layer 2 mode for Layer 2 configuration, use the switchport command in interface configuration mode. To put an interface into Layer 3 mode, use the no form of this command.

switchport

no switchport

Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers

To modify the switching characteristics of the Layer 2-switched interface, use the switchport command (without keywords). Use the no form of this command (without keywords) to return the interface to the routed-interface status and cause all further Layer 2 configuration to be erased. Use the switchport commands (with keywords) to configure the switching characteristics.

switchport

switchport {host | nonegotiate}

no switchport

no switchport nonegotiate

Syntax Description

Cisco 3550, 4000, and 4500 Series Switches

This command has no arguments or keywords.

Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers

Defaults

Cisco 3550, 4000, and 4500 Series Switches

All interfaces are in Layer 2 mode.

Catalyst 6500/6000 Series Switches and 7600 Series Routers

The default access VLAN and trunk-interface native VLAN are default VLANs that correspond to the platform or interface hardware.

Command Modes

Interface configuration

Command History

Usage Guidelines

Cisco 3550, 4000, and 4500 Series Switches

Use the no switchport command to put the interface into the routed-interface status and to erase all Layer 2 configurations. You must use this command before assigning an IP address to a routed port. Entering the no switchport command shuts down the port and then reenables it, which might generate messages on the device to which the port is connected.

You can verify the switchport status of an interface by entering the show running-config privileged EXEC command.

Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers

You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 interface before you can enter additional switchport commands with keywords. This action is required only if you have not entered the switchport command for the interface.

Entering the no switchport command shuts down the port and then reenables it. This action may generate messages on the device to which the port is connected.

To optimize the port configuration, entering the switchport host command sets the switch port mode to access, enables spanning tree PortFast, and disables channel grouping. Only an end station can accept this configuration.

Because spanning-tree PortFast is enabled, you should enter the switchport host command only on ports that are connected to a single host. Connecting other Cisco 7600 series routers, hubs, concentrators, switches, and bridges to a fast-start port can cause temporary spanning-tree loops.

Enable the switchport host command to decrease the time that it takes to start up packet forwarding.

The no form of the switchport nonegotiate command removes nonegotiate status.

When using the nonegotiate keyword, Dynamic Inter-Switch Link Protocol and Dynamic Trunking Protocol (DISL/DTP)-negotiation packets are not sent on the interface. The device trunks or does not trunk according to the mode parameter given: access or trunk. This command returns an error if you attempt to execute it in dynamic (auto or desirable) mode.

You must force a port to trunk before you can configure it as a SPAN-destination port. Use the switchport nonegotiate command to force the port to trunk.

Examples

Cisco 3550, 4000, and 4500 Series Switches

The following example shows how to cause an interface to cease operating as a Layer 2 port and become a Cisco-routed (Layer 3) port:

Router(config-if)# no switchport

Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers

The following example shows how to cause the port interface to stop operating as a Cisco-routed port and convert to a Layer 2-switched interface:

Router(config-if)# switchport

Router(config-if)#

Note The switchport command is not used on platforms that do not support Cisco-routed ports. All physical ports on such platforms are assumed to be Layer 2-switched interfaces.

The following example shows how to optimize the port configuration for a host connection:

Router(config-if)# switchport host

switchport mode will be set to access

spanning-tree portfast will be enabled

channel group will be disabled

Router(config-if)#

This example shows how to cause a port interface that has already been configured as a switched interface to refrain from negotiating trunking mode and act as a trunk or access port (depending on the mode set):

Router(config-if)# switchport nonegotiate

Router(config-if)#

The following example shows how to cause an interface to cease operating as a Cisco-routed port and to convert it into a Layer 2 switched interface:

Router(config-if)# switchport

Note The switchport command is not used on platforms that do not support Cisco-routed (Layer 3)
ports. All physical ports on such platforms are assumed to be Layer 2 switched interfaces.

Related Commands

switchport access vlan

To set the VLAN when the interface is in access mode, use the switchport access vlan command in interface configuration mode. To reset the access-mode VLAN to the appropriate default VLAN for the device, use the no form of this command.

switchport access vlan vlan-id

no switchport access vlan

Syntax Description

Defaults

The defaults are as follows:

•Access VLAN and trunk-interface native VLAN are default VLANs that correspond to the platform or interface hardware.

•All VLAN lists include all VLANs.

Command Modes

Interface configuration

Command History

Usage Guidelines

You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 interface before you can enter the switchport access vlan command. This action is required only if you have not entered the switchport command for the interface.

Entering the no switchport command shuts down the port and then reenables it. This action may generate messages on the device to which the port is connected.

The no form of the switchport access vlan command resets the access-mode VLAN to the appropriate default VLAN for the device.

Examples

This example shows how to cause the port interface to stop operating as a Cisco-routed port and convert to a Layer 2 switched interface:

Router(config-if)# switchport

Note The switchport command is not used on platforms that do not support Cisco-routed ports. All physical ports on such platforms are assumed to be Layer 2-switched interfaces.

This example shows how to cause a port interface that has already been configured as a switched interface to operate in VLAN 2 instead of the platform's default VLAN in the interface-configuration mode:

Router(config-if)# switchport access vlan 2

Related Commands

switchport mode

To set the interface type, use the switchport mode command in interface configuration mode. Use the appropriate no form of this command to reset the mode to the appropriate default mode for the device.

Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers

switchport mode {access | trunk}

no switchport mode

Cisco Catalyst 6500/6000 Series Switches

switchport mode {access | dot1q-tunnel | dynamic {auto | desirable} | trunk}

no switchport mode

Cisco 7600 Series Routers

switchport mode {access | dot1q-tunnel | dynamic {auto | desirable} | private-vlan | trunk}

no switchport mode

switchport mode private-vlan {host | promiscuous}

no switchport mode private-vlan

Syntax Description

Defaults

Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers

The default is access mode.

Cisco Catalyst 6500/6000 Switches

The default mode is dependent on the platform; it should be either dynamic auto for platforms that are intended as wiring closets or dynamic desirable for platforms that are intended as backbone switches. The default for PVLAN ports is that no mode is set.

Cisco 7600 Series Routers

The defaults are as follows:

•The mode is dependent on the platform; it should either be dynamic auto for platforms that are intended for wiring closets or dynamic desirable for platforms that are intended as backbone switches.

•No mode is set for PVLAN ports.

Command Modes

Interface configuration

Command History

Usage Guidelines

Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers

If you enter a forced mode, the interface does not negotiate the link to the neighboring interface. Ensure that the interface ends match.

The no form of the command is not supported on the Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series routers.

Cisco Catalyst 6500/6000 Switches and Cisco 7600 Series Routers

If you enter access mode, the interface goes into permanent nontrunking mode and negotiates to convert the link into a nontrunk link even if the neighboring interface does not agree to the change.

If you enter trunk mode, the interface goes into permanent trunking mode and negotiates to convert the link into a trunk link even if the neighboring interface does not agree to the change.

If you enter dynamic auto mode, the interface converts the link to a trunk link if the neighboring interface is set to trunk or desirable mode.

If you enter dynamic desirable mode, the interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode.

If you configure a port as a promiscuous or host-PVLAN port and one of the following applies, the port becomes inactive:

•The port does not have a valid PVLAN association or mapping configured.

•The port is a SPAN destination.

If you delete a private-port PVLAN association or mapping, or if you configure a private port as a SPAN destination, the deleted private-port PVLAN association or mapping or the private port that is configured as a SPAN destination becomes inactive.

If you enter dot1q-tunnel mode, PortFast Bridge Protocol Data Unit (BPDU) filtering is enabled and Cisco Discovery Protocol (CDP) is disabled on protocol-tunneled interfaces.

Examples

Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers

The following example shows how to set the interface to access desirable mode:

Router(config-if)# switchport mode access

The following example shows how to set the interface to trunk mode:

Router(config-if)# switchport mode trunk

Cisco Catalyst 6500/6000 Switches and Cisco 7600 Series Routers

The following example shows how to set the interface to dynamic desirable mode:

Router(config-if)# switchport mode dynamic desirable

Router(config-if)#

The following example shows how to set a port to PVLAN-host mode:

Router(config-if)# switchport mode private-vlan host

Router(config-if)# 

The following example shows how to set a port to PVLAN-promiscuous mode:

Router(config-if)# switchport mode private-vlan promiscuous

Router(config-if)# 

Related Commands

synchronization (IPv6)

To enable the synchronization between IPv6 Border Gateway Protocol (BGP) and your Interior Gateway Protocol (IGP) system, use the synchronization command in address family configuration mode. To enable the Cisco IOS software to advertise a network route without waiting for IGP, use the no form of this command.

synchronization

no synchronization

Syntax Description

This command has no arguments or keywords.

Command Default

BGP advertises network routes without waiting for IGP.

Command Modes

Address family configuration

Command History

Usage Guidelines

Unlike the IPv4 version of the synchronization command, the IPv6 version is disabled by default.

By default, an IPv6 BGP speaker advertises an IPv6 network route without waiting for the IGP. Use the synchronization command in address family configuration mode to synchronize routing advertisements between BGP and your IGP. This feature allows routers and access servers within an autonomous system to have the route before BGP makes it available to other autonomous systems. When synchronization is enabled, IPv6 BGP does not advertise a route to an external neighbor unless that route is local or exists in the IGP.

Use the synchronization command if routers in the autonomous system do not speak BGP.

Examples

The following example enables a router to advertise an IPv6 network route without waiting for an IGP:

router bgp 65000

address-family ipv6

 synchronization

tacacs server

To configure the TACACS+ server for IPv6 or IPv4 and enter TACACS+ server configuration mode, use the tacacs server command in global configuration mode. To remove the configuration, use the no form of this command.

tacacs server name

no tacacs server

Syntax Description

Command Default

No TACACS+ server is configured.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

The tacacs server command configures the TACACS server using the name argument and enters TACACS+ server configuration mode. The configuration is applied once you have finished configuration and exited TACACS+ server configuration mode.

Examples

The following example shows how to configure the TACACS server using the name server1 and enter TACACS+ server configuration mode to perform further configuration:

Router(config)# tacacs server server1

Router(config-server-tacacs)#

Related Commands

telnet

To log in to a host that supports Telnet, use the telnet command in user EXEC or privileged EXEC mode.

telnet host [port] [keyword]

Syntax Description

Command Modes

User EXEC
Privileged EXEC

Command History

Usage Guidelines

Table 328 lists the optional telnet command keywords.

With the Cisco IOS implementation of TCP/IP, you are not required to enter the connect or telnet command to establish a terminal connection. You can enter only the learned hostname—as long as the following conditions are met:

•The hostname is different from a command word for the router.

•The preferred transport protocol is set to telnet.

To display a list of the available hosts, use the show hosts command. To display the status of all TCP connections, use the show tcp command.

The Cisco IOS software assigns a logical name to each connection, and several commands use these names to identify connections. The logical name is the same as the hostname, unless that name is already in use, or you change the connection name with the name-connection EXEC command. If the name is already in use, the Cisco IOS software assigns a null name to the connection.

The Telnet software supports special Telnet commands in the form of Telnet sequences that map generic terminal control functions to operating system-specific functions. To issue a special Telnet command, enter the escape sequence and then a command character. The default escape sequence is Ctrl-^ (press and hold the Ctrl and Shift keys and the 6 key). You can enter the command character as you hold down Ctrl or with Ctrl released; you can use either uppercase or lowercase letters. Table 329 lists the special Telnet escape sequences.

At any time during an active Telnet session, you can list the Telnet commands by pressing the escape sequence keys followed by a question mark at the system prompt:

Ctrl-^ ?

A sample of this list follows. In this sample output, the first caret (^) symbol represents the Ctrl key, and the second caret represents Shift-6 on your keyboard:

router> ^^?

[Special telnet escape help]

^^B  sends telnet BREAK

^^C  sends telnet IP

^^H  sends telnet EC

^^O  sends telnet AO

^^T  sends telnet AYT

^^U  sends telnet EL 

You can have several concurrent Telnet sessions open and switch among them. To open a subsequent session, first suspend the current connection by pressing the escape sequence (Ctrl-Shift-6 then x [Ctrl^x] by default) to return to the system command prompt. Then open a new connection with the telnet command.

To terminate an active Telnet session, enter any of the following commands at the prompt of the device to which you are connecting:

•close

•disconnect

•exit

•logout

•quit

Examples

The following example establishes an encrypted Telnet session from a router to a remote host named host1:

router> telnet host1 /encrypt kerberos

The following example routes packets from the source system host1 to example.com, then to 10.1.0.11, and finally back to host1:

router> telnet host1 /route:example.com 10.1.0.11 host1 

The following example connects to a host with the logical name host1:

router> host1

The following example suppresses all onscreen messages from the Cisco IOS software during login and logout:

router> telnet host2 /quiet

The following example shows the limited messages displayed when connection is made using the optional /quiet keyword:

login:User2

Password:

         Welcome to OpenVMS VAX version V6.1 on node CRAW

     Last interactive login on Tuesday, 15-DEC-1998 11:01

     Last non-interactive login on Sunday,  3-JAN-1999 22:32

Server3)logout

    User2        logged out at  16-FEB-2000 09:38:27.85

Related Commands

timeout (TACACS+)

To configure the time to wait for a reply from the specified TACACS server, use the timeout command in TACACS+ server configuration mode. To return to the command default, use the no form of this command.

timeout seconds

no timeout seconds

Syntax Description

Command Default

Time to wait is 5 seconds.

Command Modes

TACACS+ server configuration (config-server-tacacs)

Command History

Usage Guidelines

Use the timeout command to set the time, in seconds, to wait for a reply from the TACACS server. If the timeout command is configured, the specified number of seconds overrides the default time of 5 seconds.

Examples

The following example shows how to configure the wait time to 10 seconds:

Router(config)# tacacs server server1

Router(config-server-tacacs)# timeout 10

Related Commands

timers (IPv6 RIP)

To configure update, timeout, hold-down, and garbage-collection timers for an IPv6 RIP routing process, use the timers command in router configuration mode. To return the timers to their default values, use the no form of this command.

timers update timeout holddown garbage-collection

no timers

Syntax Description

Command Default

Update timer: 30 seconds
Timeout timer: 180 seconds
Hold-down timer: 0 seconds
Garbage-collection timer: 120 seconds

Command Modes

Router configuration

Command History

Usage Guidelines

The timers (IPv6 RIP) command is similar to the timers basic (RIP) command, except that it is IPv6-specific.

Use the update argument to set the time interval between RIP routing updates. If no route update is received for the time interval specified by the timeout argument, the route is considered unreachable. Use the holddown argument to set a time delay between the route becoming unreachable and the route being considered invalid in the routing table. The use of a hold-down interval is not recommended for RIP because it can introduce long delays in convergence. Use the garbage-collection argument to specify the time interval between a route being considered invalid and the route being purged from the routing table.

The basic timing parameters for IPv6 RIP are adjustable. Because IPv6 RIP is executing a distributed, asynchronous routing algorithm, it is important that these timers be the same for all routers and access servers in the network.

Note The current and default timer values are displayed in the output of the show ipv6 rip EXEC command. The relationships of the various timers should be preserved, as described previously.

Examples

The following example sets updates to be broadcast every 5 seconds. If a route is not heard from in 15 seconds, the route is declared unusable. Further information is suppressed for an additional 10 seconds. Assuming no updates, the route is flushed from the routing table 20 seconds after the end of the hold-down period.

Router(config)# ipv6 router rip cisco

Router(config-rtr)# timers 5 15 10 30

Caution By setting a short update period, you run the risk of congesting slow-speed serial lines. Also, if you have many routes in your updates, you can cause the routers to spend an excessive amount of time processing updates.

Related Commands

timers active-time

To adjust Enhanced Interior Gateway Routing Protocol (EIGRP) routing wait time, use the timers active-time command in router configuration mode or address-family topology configuration mode. To disable this function, use the no form of the command.

timers active-time [time-limit | disabled]

no timers active-time

Syntax Description

Command Default

This command is disabled by default.

Command Modes

Router configuration (config-router)
Address-family topology configuration (config-router-af-topology)

Command History

Usage Guidelines

In EIGRP, there are timers that control the time that the router waits (after sending a query) before declaring the route to be in the stuck in active (SIA) state.

Examples

In the following example, the routing wait time is 200 minutes on the specified route:

Router(config)# router eigrp 5

Router(config-router)# timers active-time 200

In the following example, the routing wait time is 200 minutes on the specified address-family route:

Router(config)# router eigrp virtual-name

Router(config-router)# address-family ipv4 autonomous-system 4453

Router(config-router-af)# network 10.0.0.0

Router(config-router-af)# topology base

Router(config-router-af-topology)# timers active-time 200

In the following example, the routing wait time is indefinite if a route becomes active:

Router(config)# router eigrp 5

Router(config-router)# timers active-time disabled

In the following example, the routing wait time is indefinite on the specified address-family route:

Router(config)# router eigrp virtual-name

Router(config-router)# address-family ipv4 autonomous-system 4453

Router(config-router-af)# network 10.0.0.0

Router(config-router-af)# topology base

Router(config-router-af-topology)# timers active-time disabled

In the following example, the routing wait time is 100 minutes on the specified route:

Router(config)# ipv6 router eigrp 1

Router(config-router)# timers active-time 100

In the following example, the routing wait time is 100 minutes on the specified address-family route:

Router(config)# router eigrp virtual-name

Router(config-router)# address-family ipv6 autonomous-system 4453

Router(config-router-af)# topology base

Router(config-router-af-topology)# timers active-time disabled

Related Commands

timers lsa arrival

To set the minimum interval at which the software accepts the same link-state advertisement (LSA) from Open Shortest Path First version 3 (OSPFv3) neighbors, use the timers lsa arrival command in OSPFv3 router configuration mode. To restore the default value, use the no form of this command.

timers lsa arrival milliseconds

no timers lsa arrival

Syntax Description

Defaults

1000 milliseconds

Command Modes

OSPFv3 router configuration (config-router)

Command History

Usage Guidelines

The timers lsa arrival command controls the minimum interval for accepting the same LSA. The "same LSA" is defined as an LSA instance that contains the same LSA ID number, LSA type, and advertising router ID. If an instance of the same LSA arrives sooner than the interval that is set, the LSA is dropped.

We suggest you keep the milliseconds value of the timers lsa arrival command less than or equal to the neighbors' hold-interval value of the timers throttle lsa all command.

Examples

The following example sets the minimum interval for accepting the same LSA at 2000 milliseconds:

router ospfv3 1

 log-adjacency-changes

 timers throttle lsa all 200 10000 45000

 timers lsa arrival 2000

 network 10.10.4.0 0.0.0.255 area 24

 network 10.10.24.0 0.0.0.255 area 24

Related Commands

timers pacing flood (OSPFv3)

To configure link-state advertisement (LSA) flood packet pacing, use the timers pacing flood command in Open Shortest Path First version 3 (OSPFv3) router configuration mode. To restore the default flood packet pacing value, use the no form of this command.

timers pacing flood milliseconds

no timers pacing flood

Syntax Description

Command Default

The default is 33 milliseconds.

Command Modes

OSPFv3 router configuration (config-router)

Command History

Usage Guidelines

Configuring Open Shortest Path First version 3 (OSPF) flood pacing timers allows you to control interpacket spacing between consecutive link-state update packets in the OSPFv3 transmission queue. This command allows you to control the rate at which LSA updates occur to reduce the high CPU or buffer utilization that can occur when an area is flooded with a very large number of LSAs.

The default settings for OSPFv3 packet pacing timers are suitable for the majority of OSPFv3 deployments. Do not change the packet pacing timers unless all other options to meet OSPFv3 packet flooding requirements have been exhausted. Specifically, network operators should prefer summarization, stub area usage, queue tuning, and buffer tuning before changing the default flood timers. Furthermore, there are no guidelines for changing timer values; each OSPFv3 deployment is unique and should be considered on a case-by-case basis.

Note The network operator assumes risks associated with changing the default flood timer values.

Examples

The following example configures LSA flood packet-pacing updates to occur in 20-millisecond intervals for OSPFv3 routing process 1:

Router(config)# router ospfv3 1

Router(config-router)# timers pacing flood 20

Related Commands

timers pacing lsa-group (OSPFv3)

To change the interval at which Open Shortest Path First version 3 (OSPFv3) link-state advertisements (LSAs) are collected into a group and refreshed, checksummed, or aged, use the timers pacing lsa-group command in router configuration mode. To restore the default value, use the no form of this command.

timers pacing lsa-group seconds

no timers pacing lsa-group

Syntax Description

Command Default

The default interval for this command is 240 seconds. OSPFv3 LSA group pacing is enabled by default.

Command Modes

OSPFv3 router configuration (config-router)

Command History

Usage Guidelines

This command allows you to control the rate at which LSA updates occur to reduce the high CPU or buffer utilization that can occur when an area is flooded with a very large number of LSAs. The default settings for OSPFv3 packet pacing timers are suitable for the majority of OSPFv3 deployments. Do not change the packet pacing timers unless all other options to meet OSPFv3 packet flooding requirements have been exhausted. Specifically, network operators should prefer summarization, stub area usage, queue tuning, and buffer tuning before changing the default flooding timers. Furthermore, there are no guidelines for changing timer values; each OSPFv3 deployment is unique and should be considered on a case-by-case basis.

Note The network operator assumes the risks associated with changing the default timer values.

Cisco IOS software groups the periodic refresh of LSAs to improve the LSA packing density for the refreshes in large topologies. The group timer controls the interval used for group refreshment of LSAs; however, this timer does not change the frequency that individual LSAs are refreshed (the default refresh rate is every 30 minutes).

The duration of the LSA group pacing is inversely proportional to the number of LSAs the router is handling. For example, if you have about 10,000 LSAs, decreasing the pacing interval would benefit you. If you have a very small database (40 to 100 LSAs), increasing the pacing interval to 10 to 20 minutes might benefit you slightly.

Examples

The following example configures OSPFv3 group packet-pacing updates between LSA groups to occur in 300-second intervals for OSPFv3 routing process 1:

Router(config)# router ospfv3 1

Router(config-router)# timers pacing lsa-group 300 

Related Commands

timers pacing retransmission (OSPFv3)

To configure link-state advertisement (LSA) retransmission packet pacing in IPv4 Open Shortest Path First version 3 (OSPFv3), use the timers pacing retransmission command in OSPFv3 router configuration mode. To restore the default retransmission packet pacing value, use the no form of this command.

timers pacing retransmission milliseconds

no timers pacing retransmission

Syntax Description

Command Default

The default is 66 milliseconds.

Command Modes

OSPFv3 router configuration (config-router)

Command History

Usage Guidelines

Configuring OSPFv3 retransmission pacing timers allow you to control interpacket spacing between consecutive link-state update packets in the OSPFv3 retransmission queue. This command allows you to control the rate at which LSA updates occur to reduce high CPU or buffer utilization that can occur when an area is flooded with a very large number of LSAs. The default settings for OSPFv3 packet retransmission pacing timers are suitable for the majority of OSPFv3 deployments. Do not change the packet retransmission pacing timers unless all other options to meet OSPFv3 packet flooding requirements have been exhausted. Specifically, network operators should prefer summarization, stub area usage, queue tuning, and buffer tuning before changing the default flooding timers. Furthermore, there are no guidelines for changing timer values; each OSPFv3 deployment is unique and should be considered on a case-by-case basis.

Note The network operator assumes risks associated with changing the default packet retransmission pacing timer values.

Examples

The following example configures LSA flood pacing updates to occur in 100-millisecond intervals for OSPFv3 routing process 1:

Router(config)# router ospfv3 1

Router(config-router)# timers pacing retransmission 100

Related Commands

timers register

To set how long the Session Initiation Protocol (SIP) user agent (UA) waits before sending register requests, use the timers register command in SIP user-agent configuration mode. To reset this value to the default, use the no form of this command.

timers register milliseconds

no timers register

Syntax Description

Defaults

500 milliseconds

Command Modes

SIP user-agent configuration

Command History

Examples

The following example sends register requests every 500 milliseconds:

sip-ua 

 retry invite 9

 retry register 9

 timers register 500

Related Commands

timers spf (IPv6)

To turn on Open Shortest Path First (OSPF) for IPv6 shortest path first (SPF) throttling, use the timers spf command in router configuration mode. To turn off SPF throttling, use the no form of this command.

timers spf delay holdtime

no timers spf

Syntax Description

Command Default

OSPF for IPv6 throttling is always enabled.

Command Modes

Router configuration

Command History

Usage Guidelines

The first wait interval between SPF calculations is the amount of time in milliseconds specified by the delay argument. Each consecutive wait interval is two times the current hold level in milliseconds until the wait time reaches the maximum time in milliseconds as specified by the holdtime argument. Subsequent wait times remain at the maximum until the values are reset or a link-state advertisement (LSA) is received between SPF calculations.

Examples

The following example shows a router configured with the delay and hold-time interval values for the timers spf command set at 40 and 50 milliseconds, respectively.

Router(config)# ipv6 router ospf 1

Router(config-router)# timers spf 40 50

Related Commands

timers throttle lsa

To set rate-limiting values for Open Shortest Path First (OSPF) for IPv6 link-state advertisement (LSA) generation, use the timers throttle lsa command in router configuration mode. To restore the default values, use the no form of this command.

timers throttle lsa start-interval hold-interval max-interval

no timers throttle lsa

Syntax Description

Defaults

start-interval: 0 milliseconds
hold-interval: 5000 milliseconds
max-interval: 5000 milliseconds

Command Modes

OSPF for IPv6 router configuration (config-rtr)
Router configuration (config-router)

Command History

Usage Guidelines

The "same LSA" is defined as an LSA instance that contains the same LSA ID number, LSA type, and advertising router ID. We suggest you keep the milliseconds value of the timers lsa arrival command less than or equal to the hold-interval value of the timers throttle lsa command.

Examples

This example customizes OSPF LSA throttling so that the start interval is 200 milliseconds, the hold interval is 10,000 milliseconds, and the maximum interval is 45,000 milliseconds. The minimum interval between instances of receiving the same LSA is 2000 milliseconds.

router ospf 1

 log-adjacency-changes

 timers throttle lsa 200 10000 45000

 timers lsa arrival 2000

 network 10.10.4.0 0.0.0.255 area 24

 network 10.10.24.0 0.0.0.255 area 24

This example customizes IPv6 OSPF LSA throttling so that the start interval is 500 milliseconds, the hold interval is 1,000 milliseconds, and the maximum interval is 10,000 milliseconds.

ipv6 router ospf 1 

 log-adjacency-changes

 timers throttle lsa 500 1000 10000 

Related Commands

timers throttle spf

To turn on Open Shortest Path First (OSPF) shortest path first (SPF) throttling, use the timers throttle spf command in the appropriate configuration mode. To turn off OSPF SPF throttling, use the no form of this command.

timers throttle spf spf-start spf-hold spf-max-wait

no timers throttle spf spf-start spf-hold spf-max-wait

Syntax Description

Command Default

SPF throttling is not set.

Command Modes

Address family configuration (config-router-af)
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)
OSPF for IPv6 router configuration (config-rtr)

Command History

Usage Guidelines

The first wait interval between SPF calculations is the amount of time in milliseconds specified by the spf-start argument. Each consecutive wait interval is two times the current hold level in milliseconds until the wait time reaches the maximum time in milliseconds as specified by the spf-max-wait argument. Subsequent wait times remain at the maximum until the values are reset or a link-state advertisement (LSA) is received between SPF calculations.

Release 12.2(33)SRB

If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the timers throttle spf command in router address family topology configuration mode in order to make this OSPF router configuration command become topology-aware.

Examples

The following example shows how to configure a router with the delay, hold, and maximum interval values for the timers throttle spf command set at 5, 1000, and 90,000 milliseconds, respectively.

router ospf 1

 router-id 10.10.10.2

 log-adjacency-changes

 timers throttle spf 5 1000 90000 

 redistribute static subnets

 network 10.21.21.0 0.0.0.255 area 0

 network 10.22.22.0 0.0.0.255 area 00

The following example shows how to configure a router using IPv6 with the delay, hold, and maximum interval values for the timers throttle spf command set at 500, 1000, and 10,000 milliseconds, respectively.

ipv6 router ospf 1 

 event-log size 10000 one-shot

 log-adjacency-changes  

 timers throttle spf 500 1000 10000