routing question

Unanswered Question
Jun 12th, 2007

Hello, I have a router conecting 2 switches. Fa0/0 connected switch A & Fa0/1 connected switch B. My ISP on serial interfaces of my router. What I want to do is: If one interface f0/0 is active and goes down the F0/1 become active.

How can I do it?

thanks

Regards

I have this problem too.
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spremkumar Tue, 06/12/2007 - 20:20

Hi Sundar

If the user wants to re route the traffic via Fa0/1 when the link connected via Fa0/0 is down i dont think backup interface command will be effective coz the Ethernet interface wont go down though there is some issue with the link connected onto it..

I feel you were referring the behavior of the command with serial/bri interface which is totally different in the case of serial/bri interfaces where backup command works effectively...

In the above mentioned scenario i feel the user has to make use of tracking feature or else he need to create GRE tunnels over ther SP and have the routing done...

I feel the second option may not be viable coz the SP's may not allow for GRE config in their Access boxes...

regds

sundar.palaniappan Tue, 06/12/2007 - 20:37

Edwin,

What you are saying is true if the ethernet is connected to the ISP via DSL or cable. If it's connected through cable or DSL then that would warrant the use of feature like reliable static route using object tracking because even when the interface is up it mayn't pass traffic always.

However, in this case the Internet connection is through a serial int and the two ethernet interfaces connect to their LAN. Unless it's a fiber link which is susceptible to unidirectional link problems the ethernet interface would almost go down always and thus the backup interface is a very viable option. Even to address the unidirectional link a feature like UDLD can be enabled to detect/disable the UDLD link.

HTH

Sundar

spremkumar Tue, 06/12/2007 - 20:43

Hi Sundar

Thx for clarifying it out.. :-).

I felt the user has connected the ISP links on the ethernet port and thats where i suggested implementation of tracking feature...

regds

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