Hi,
I have a network with a 5412R zl2 as the core switch, and several stacks of 4 2920s, each stack almost identically configured ( same VLANs, some small differences in which ports are assigned to which VLAN ). These are "real" stacks with stacking modules and cables, configured as a ring. There is a single Aruba 7200 wireless controller connected to the 5412, with a number of APs connected to each stack. Each stack has two fibre links back to the core and spanning tree is enabled.
After a period of some days one specific stack (always the same one ) will stop passing traffic to newly connected edge devices. Traffic via the Aruba APs connected to the same stack ( tunelled back to the controller ) is unaffected, and so wireless becomes the only practical way to access the switch
When the fault arises approx 80% of pings from wired devices are dropped. ssh'ing in to the stack via wireless and trying to ping a device connected to the stack nearly always fails. The MAC addresses of the device I can't ping shows in the output of show mac-address
It appears that this connectivity issue is limited to VLAN 1 ( which is untagged across all uplinks and most edge ports ) which is the VLAN that contains the switches, servers and PCs.
I appreciate that having all that equipment in a single VLAN, using VLAN 1, and having VLAN 1 untagged across all switches isn't best practice, but I dont "own" this network and I'm not in a position to get any of this changed.
If I remove one stacking cable between members 2 and 3, then members 1 and 2 start to work perfectly. Members 3 and 4 have no connectivity, despite it being a broken ring, not a chain.
A restart of the whole stack resolves the issue.
As I say, this only occurs on one stack. The other 8 stacks of 2920s all work exactly as I'd expect.
Any ideas welcome!