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Frame-Relay Keepalives and Static Routing Tables

Unanswered Question
Apr 2nd, 2003
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How do Frame-Relay Keepalives affect routing tables when using

static routes that point to a Next-Hop-Address versus using static

routes that point to the local serial (sub)interface ? I know that if

you point to the local interface versus a next-hop-address and the

frame link causes a change in the serial interface's status that the

routes are dropped from the routing table much quicker than they

would be dropped from the routing table if the static route pointed

to the next-hop-address. Please advise.

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rbristow Thu, 04/03/2003 - 11:26
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LMI is the protocol between the router's FR interface and the carrier's FR edge switch. If you disable keepalives on the FR interface, you're turning off LMI. This is a bad idea, since LMI keepalive packets let the router know when PVC's are up or not (see status on every 6th LMI update). Without LMI the router would never flag a PVC as down.

Regards,

Rob Bristow

CCIE #3335

m-may Thu, 04/03/2003 - 12:14
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Rob,

Are LMI keepalives enabled by default on a cisco router ? I've never manually

disabled it and I was given the following configuration statements by a customer

of our's. I'm curious... If the following statements aren't in a router's configuration,

does that mean LMI isn't enabled for a given interface ?


Global Config Mode:

map-class frame-relay keepalive

frame-relay end-to-end keepalive mode bidirectional


(Sub)Interface Mode:

frame-relay class keepalive


Please advise.


Thanks,

Mike

phusein Tue, 04/08/2003 - 15:20
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Hi Mike,

The lmi keepalives are enabled by default on the interface, regardless of whether or not yo have the map-class. You can tell this by looking at the output of show frame-relay lmi. You'll see the lmi status frames being sent and recieved.

The map-class allows you to monitor/manage each pvc per sub-interface, by sending keepalives back and forth between pvc end points.

Hope that helps

Parvez

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