In the frame relay cloud, under certain unusual circumstances (including a
trunk line that goes unidirectional), the one or both edge frame relay
switches may not see the outage. LMI will therefore not report the failure
from the edge switch to the router, the PVC status is not changed on the
router, and you have an interface up/up even though it doesn't work.
In IOS 12.1+, you can configure "frame-relay end-to-end keepalive" on the
routers to get around this kind of failure. This command tells both routers
to force the interface down if they cannot communicate across the link, even
if LMI from the switch reports the PVC is active.
Without an IOS that new, you'll have to rely on your DBU log entries to
document the problem. It may help if you manually try to ping across the
link (i.e. use extended ping to force the pings across the frame relay
subinterfaces instead of the dbu) so you can tell ATT point blank that both
routers are up and working, but the PVC is not. With MCI, you can open a
ticket and have it sent to their Hyperstream or Concert Frame groups and try
to get a tech who understands this kind of failure (some do, many don't). At
ATT, I believe the equivalent group is the "backbone" group, but don't quote
me on that.
HTH,
doctorcisco
Silicon ... just fancy sand.
>Hello,
>
>We have AT&T frame line between US and Asia. Sometimes
>frame line is not available (therefore ISDN backup
>kicked in). But the weird thing is on both side frame
>routers, show serial interface says up. I couldn't
>ping between the 2 frame routers. Worse, on the syslog
>server, the link down was not captured 'cause the
>serial were still "up".
>
>What can I do to collect some fact and data so I can
>yell at AT&T?
>
>Thanks in advance.
>
>Jim
>
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