backup interface problem

Unanswered Question
Feb 12th, 2007


I have a Cisco 2811 router,which has 2 fastethernet ports ,WIC-1T card.

1. WIC-1T is connected to teh ISP by means of 128KB leased line.

2. Fastethernet 0 is configured with Public STatic IP and connected to a switch,where 5 usres are connected with public IP.

3. Then the second fastethernet 1 interface is connected to a ADSL modem provided by the same ISP.

Now I want to configure this fastethernet 1 as the backup interface for teh Serial interface.

Please guide me how to achieve this.

Thanks and Regards,


I have this problem too.
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Anonymous (not verified) Fri, 02/16/2007 - 14:10

Why do you want to configure your fast ethernet interface as the backup interface to the serial interface?? Normally only a serial interface should be used to act as a back up for another serial interface. You cannot configure a fast ethernet interface as a backup for serial interface.

Lavanholy Fri, 02/16/2007 - 20:05

Hi Joas,

Thanks for your info.I have completed day before yesterday.It is working fine.I have 2 Fastethernet and 1 WIC-1T,The WIC-1T is connected to ISP.

F0/1 is assigned as the global public IP and it is attached to the PROXY server's one of the NIC which is also assigned as the Global Public IP.

F0/0 is defined as the backup interface for the Serial interface,F0/0 is private IP to which LAN interface of the ADSL is attached whose IP also in the same subnet IP of F0/0.

Now whenever the serial interface is down teh fastethernet 0/0 is coming up and we are able to access the Internet.

Thanks a lot.

Best Regards,



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