The Universal Switching Module (UXM) inverse multiplexing for ATM (IMA) group using the T1 back card experiences "IMA Group Failure" when there is a clock switch on the node. This leads to temporary Communication Breaks and clock switches on downstream nodes if the failed trunk is the source of clock. This may result in unreachable nodes if there are no other types of trunks to the node. The IGX must experience a clock switch to trigger the "IMA Group Failure." This should not affect nodes using Internal Oscillator as the clock source.
Customers note network nodes being unreachable after a clock switch. The cause is unknown and is currently under investigation.
Unreachability results if there are only IMA trunk groups to the node.
Remove IMA trunk group(s).
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