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mfaust Mon, 07/08/2002 - 12:55
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In order to have frame relay connectivity end to end, several things must occur. When the physical link between the router and the frame relay switch is established, the router will show the interface "up". Once the interface is "up", the router will begin sending LMI packets to the switch and the switch will respond to them. When this process is functional, the router will show the line protocol "up".

The next step is to have the PVC become active. The router knows if the PVC is active by the "active" bit in the "LMI Full Status Update" from the switch. Here is where it can get tricky. The frame relay switch needs to see all conditions good, end to end, before it will places the PVC in the active state.

In other words: router - UNI - switch - NNI(s) - switch - UNI - router. If there is a failure anywhere in this path the switches will place the PVC in the "inactive" state. When trouble shooting a problem such as this, you need to look at the entire circuit, not just the local end. Here is what I would suggest: Look carefully at the routers at both ends to ensure that there is not problem. Do some debugs on the LMI (I think this will work "debug frame-relay lmi"). Look for indications of state changes in the LMI packets. If you have a protocol anylizer, use it and filter for the LMI packets. If you are not getting the status bit set to "inactive", yet the PVC goes down, look internally for a problem. If the status bit is set to "inactive", look toward the transport network to find out why. Be sure to do your investigation at both ends of your circuit to eliminate your equipment.

Good luck!!!



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