When your Serial Links Flap!

Jay Greenberg · Posted: Mon Oct 18, 2004 8:12 am Post subject: When your Serial Links Flap!

There are 2 probable issues to consider when resolving a serial link flapping issue, from a configuration standpoind.

1) The Clock Rate is not Set
All Back to Back serial connections require the DCE end to have a clock rate set. This is done with the command:
Router(config-if)# clock rate <rate>

2) The Clock Rate is set incorrectly on Pod2/R3
Routers with low speed serial interfaces, such as R3, require that the DCE interfaces to be clocked at a lower speed. Even though the command may allow you to enter a higher clock rate, please use the command:
Router(config-if)# clock rate 56000

Please let me know if you have anything to add to these notes.