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Webcast-Catalyst9k
New Member

ISDN Question

Router 1-------------Router 2---------------------------------Router 3

|========================================|

----- Lease Line

===== ISDN Backup

Router 1 connected by L.L1 to Router 2 ,

Router 2 connected by L.L2 to Router 3 ,

Router 1 & Router 3 have ISDN Backup

If L.L1 disconnects, Router 1 will start the ISDN Backup which is connected to Router 3.

If L.L2 disconnects, Router 3 will start the ISDN Backup which is connected to Router 1.

My question is that if one of the L.L disconnects say L.L1, and the ISDN starts,

router one will connect itself to Router 3 through the ISDN line, but when Router 2

wants to pass data to Router 1, it won't work because the L.L is disconnected and the

routing table for Router 2 can't change thus it can't pass the data. What are some possible

solution to this problem.

If the diagram of the description of the problem is not clear, please email me and I'll try

to explain it better. Thank you

PS: My customer do not repare dynamic routing ...

1 REPLY
New Member

Re: ISDN Question

You can run a dynamic routing protocol over ISDN but ensure in the dialer-list

that e.g. EIGRP is not allowed to open the ISDN connection.

And also ensure that the metric over the leased lines is better than over ISDN

or the backup won't switch back after the leased line has recovered.

regards Ulrich Marzoli

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