Monitoring Reliable Static Routing

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Reliable static routes silently appear or disappear from the IP routing table based on the state of the attached track object; the only way to monitor their state is to use the show ip route track-table command or the debug track command.

Show tracked routes
GW#show ip route track-table
 ip route 0.0.0.0 0.0.0.0 Serial0/0/0 10 name ISP_A track 100 state is [down]
Debug tracking
GW#debug track
06:49:44: Track: 100 Down change delayed for 10 secs
06:49:54: Track: 100 Down change delay expired
06:49:54: Track: 100 Change #26 rtr 100, reachability Up->Down
06:50:24: Track: 100 Up change delayed for 20 secs
06:50:34: Track: 100 Up change delay cancelled
06:58:59: Track: 100 Up change delayed for 20 secs
06:59:19: Track: 100 Up change delay expired
06:59:19: Track: 100 Change #25 rtr 100, reachability Down->Up
The debugging printout illustrates a real-life scenario where the next-hop router became temporarily reachable during the bootstrap process and disappeared a few seconds later (the change delay cancelled printout).

While the silent modification of the IP routing table might be acceptable in most situations (after all, you don’t get notified when a regular IP route disappears from the routing table either), you might want to know if your primary ISP is unreachable (similar to the interface up/down events you would get with traditional access methods like leased lines or Frame Relay access). The Embedded Event Manager 2.2 (introduced in IOS release 12.4(2)T) is the ideal solution, as you can trigger EEM applets (or TCL scripts) whenever a track object’s state changes with the event track configuration command.

To display the changes in a tracked object state, you can define two EEM applets: one triggered on the down change and another triggered on the up change. The only action you need to specify to be notified that the state has changed is the syslog msg action; you can add other actions, like sending an email to the network manager or even reconfiguring the router. The following printouts show a sample EEM configuration and the printouts it generates.

IOS EEM applet generates syslog messages on tracked object state change
event manager applet ISP_A_down
 event track 100 state down
 action 1.0 syslog msg "ping to 172.16.1.2 from Serial 0/0/0 failed"
event manager applet ISP_A_up
 event track 100 state up
 action 1.0 syslog msg "172.16.1.2 is reachable"
Sample EEM printouts
07:02:19: %HA_EM-6-LOG: ISP_A_down: ping to 172.16.1.2 from Serial 0/0/0 failed
07:03:19: %HA_EM-6-LOG: ISP_A_up: 172.16.1.1 is reachable

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