backup interface

Unanswered Question
Feb 9th, 2008

Is it possible to have a fastethernet interface as a backup of more than one serial lines on a 7507 router ?

I have this problem too.
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Goutam Sanyal Sat, 02/09/2008 - 01:51


If I assume that you want FastEthernet as a backup interface of Serial so it is possible. Also its depends how your network is designed.


Router(config)#inty ser 0/0/0

Router(config-if)#backup interface fastEthernet ?

<0-0> FastEthernet interface number



pls rate if it works.

kon_salev Sat, 02/09/2008 - 02:16

I use a 7507 with 15 serial lines and a second 7507 with 5 adsl-vpn lines. The two routers are connected together with fastethernet. I want to use the fastethenet for backup of all 15 seials.

Richard Burts Sat, 02/09/2008 - 05:38


While it may work for one interface I believe that trying to use any interface as backup for more than 1 interface is a problem. This is because the backup interface is put into a special state while the primary is up and the backup only becomes active when the primary is down. So if the FastEthernet is backup for serial 1 and 2 and serial 1 goes down I believe that the FastEthernet will not activate until both interfaces go down.

Perhaps an alternative might be to create a trunk on the FastEthernet with VLAN subinterfaces going over the trunk. Then you could use a subinterface as backup for the serial.




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