Hi All,
We have two DAD links configured on our Cisco 9500 StackWise Virtual switches. Both the DAD links originally used GLC-SX-MMD over MM fibre.
We found that any changes to the DAD link would bring down the DAD link and required a reload of the stack to restore normal operation on the link. (Our changes are summarised below)
1. DAD link was operating normally on Tw1/0/23 & Tw2/0/23 using GLC-SX-MMD over MM fibre.
2. Changed SFPs on port Tw1/0/23 & Tw2/0/23 from GLC-SX-MMD to GLC-LH-SMD and patched the DAD link using SM fibre.
3. Observed that the DAD link went down and would not come back up. (confirmed that the SFPs and SM fibre was working normally by patching it to different spare switches)
4. Changed SFPs on port Tw1/0/23 & Tw2/0/23 back to GLC-SX-MMD and patched the link using the original MM fibre.
5. Observed that the DAD link would still not come back up.
6. Rebooted the whole 9500 switch stack and found that the DAD link was operational again.
7. Change the SFPs back to GLC-LH-SMD and patched the DAD link using SM fibre. Observed that the DAD link went down and would not come back up.
8. Rebooted the whole 9500 switch stack and found that the DAD link was now operational over the SM fibre.
Has anyone come across this issue and know a workaround? This looks like an IOS bug.
I have raised a TAC case and waiting for answers.
