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max-metric router-lsa
Enables the stub router advertisement to advertise a maximum metric value during BGP convergence on router startup or reload.
Syntax: max-metric router-lsa [on-startup {timer timeoutVal | wait-for-bgp route-threshold thresholdVal}]
thresholdVal
Specifies the number, in 1K increments, of BGP best routes that must converge before BGP convergence is considered complete for purposes of maximum metric advertisement. Valid values: 0 - 450000. Default: none or infinite if keyword not specified.
timeoutVal
Specifies timeout value, in seconds, for terminating maximum metric advertisement should BGP convergence not be reached before timer expires. Valid values: 5 - 600. Default: 600.
Description: The advertising of a maximum metric during startup allows routing tables to converge before traffic destined for other networks is sent through the router. This functionality is implemented in the OSPF stub router maximum metric advertisement feature defined in RFC 3137.
OSPF stub router maximum metric advertisement provides for the bringing up of a new router into a network without immediately routing traffic through the new router, as well as, gracefully shutting down and reloading a router without dropping packets that are destined for other networks. The maximum metric advertisement feature introduces a BGP configuration option, that allows a router running the OSPF protocol to advertise a maximum or infinite metric of link state infinity (0xFFFF) to all neighbors, making this router the least preferred router in the network for forwarding traffic to another network.
There are two mechanisms used to determine the end of the maximum metric advertisement. The BGP best routes learned threshold limit is used to identify the completion of BGP convergence. When this configurable threshold is reached, the maximum metric advertisement is replaced with the normal OSPF metric value. The expiration of a configurable timer that defaults to 600 seconds will also replace the maximum metric with the normal OSPF metric value should BGP convergence completion fail to take place within the timer period. The maximum metric advertisement configuration is ignored during NSR® failover, where the continued forwarding of OSPF packets is inherent to the NSR® functionality.
Use the max-metric router-lsa command, in router configuration mode, to enable maximum metric advertisement for this router that persists after BGP convergence completion.
Use the max-metric router-lsa on-startup wait-for-bgp route-threshold command to specify a BGP routing table convergence threshold that when met will terminate the maximum metric advertisement state. There is a time-out option that can be added to configure a time out value other than the 600 second default.
Factory Default: Disabled.
Command Mode: Router configuration.
Example 1: In the following example:
- The maximum metric advertisement is enabled for router 12
- The BGP route threshold is set to 240K routes
- The time-out setting is changed to 300 seconds:
router(config)#router ospf 12
router(config-router)#max-metric router-lsa on-startup wait-for-bgp route-threshold 240000 time-out 300
router(config-router)end
router#
Example 2: In the following example: the maximum metric advertisement is disabled for router 12
router(config)#router ospf 12
router(config-router)#no max-metric router-lsa
router(config-router)end
router#
Related Commands: router ospf
timers spf
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Copyright © 2004
Avici Systems Inc.
Avici® and TSR®
is a registered trademark of Avici Systems Inc.
IPriori™, Composite Links™, SSR™, QSR, and NSR® are
trademarks of Avici Systems Inc.
Source
File Name: ospf.fm
HTML File Name: ospf17.html
Last Updated: 05/10/04 at 16:34:58