Can ISDN used as backup link for Metro-E trunk? Can it be done?

Unanswered Question
Apr 7th, 2008
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Hi experts,

I got critical issue since my Metro-e trunk unable to be backup with ISDN. The issue is that, when the Metro-e trunk is down, the ISDN is not triggered since the fastethernet port at router still in UP status, which unable to force the ISDN to trigger automatically. Currently, I m using backup interface method which applied at Fasethernet interface at router like below:

interface FastEthernet1/0

description *** Metro-E Trunk **

ip address

backup interface dialer1

backup delay 5 60

duplex full

speed auto


*comment: Fastethernet1/0 still UP although Metro-E trunk is DOWN.

On design site, the router is connected to fiber-converter which has two ports, one for fiber (metro-e) port and another one is LAN port connecting to the router fastethernet interface.

Is there any methods which can force the ISDN to trigger automatically although the fastethernet status still UP?? Thank you.

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noroutes4u Mon, 04/07/2008 - 06:29
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Are you running any routing protocol across this Metro-E Trunk? If you are, then the routing protocol should react when that trunk is down. A floating static route via the isdn link will then be used and your interesting traffic will trigger the connection.

manmeetmarwah Mon, 04/07/2008 - 21:33
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You can create a GRE tunnel and can put the backup command on the tunnel interface to achieve this.


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