Cisco Systems 78-11741-02 manual Logging Neighbors Going Up or Down, Changing the LSA Group Pacing

Configuring OSPF

Logging Neighbors Going Up or Down

Implementation Considerations

Evaluate the following considerations before implementing this feature:

•Because LSAs that include topology changes are flooded over an on-demand circuit, we recommend that you put demand circuits within OSPF stub areas or within NSSAs to isolate the demand circuits from as many topology changes as possible.

•To take advantage of the on-demand circuit functionality within a stub area or NSSA, every router in the area must have this feature loaded. If this feature is deployed within a regular area, all other regular areas must also support this feature before the demand circuit functionality can take effect because type 5 external LSAs are flooded throughout all areas.

•Hub-and-spoke network topologies that have a point-to-multipoint (p2mp) OSPF interface type on a hub might not revert back to non-demand circuit mode when needed. You must simultaneously reconfigure OSPF on all interfaces on the p2mp segment when reverting them from demand circuit mode to non-demand circuit mode.

•Do not implement this feature on a broadcast-based network topology because the overhead protocols (such as hello and LSA packets) cannot be successfully suppressed, which means the link will remain up.

•Configuring the router for an OSPF on-demand circuit with an asynchronous interface is not a supported configuration. The supported configuration is to use dialer interfaces on both ends of the circuit. For more information, refer to the following TAC URL:

http://www.cisco.com/warp/public/104/dcprob.html#reason5

Logging Neighbors Going Up or Down

By default, the system sends a syslog message when an OSPF neighbor goes up or down. If you turned off this feature and want to restore it, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# log-adjacency-changes	Sends syslog message when an OSPF neighbor goes up or down.
[detail]

Configure this command if you want to know about OSPF neighbors going up or down without turning on the debug ip ospf adjacency EXEC command. The log-adjacency-changesrouter configuration command provides a higher level view of the peer relationship with less output. Configure log-adjacency-changes detail if you want to see messages for each state change.

Changing the LSA Group Pacing

The OSPF LSA group pacing feature allows the router to group OSPF LSAs and pace the refreshing, checksumming, and aging functions. The group pacing results in more efficient use of the router.

The router groups OSPF LSAs and paces the refreshing, checksumming, and aging functions so that sudden increases in CPU usage and network resources are avoided. This feature is most beneficial to large OSPF networks.

Cisco IOS IP Configuration Guide

IPC-235