Problem found:sw4500#sho platform hardware floodset vlan 4 Executing the command on VSS member switch role = VSS Active, id = 1Vlan 4:Unicast Floodset: FloodToCpu: - RetIndex: 4 Po16(848)  Po21(853)  Po23(855)  Po24(856)  Po31(863)  Po51(883)  Po14(...

Maybe to point which might be relevant- The passive 4500X was completely broken, it was replaced by a new one.- We have an additional module:2     8  10GE SFP+                              C4KX-NM-8I don't know if only these interfaces have problems

I have done some additional tests:New theory:- Packet coming in on the passive switch which can be directly sent to an interface on the passive switch don't update the mac address table.Result:- If incoming packet on the passive switch has destinatio...

After some tests I had to adjust mij theory:If a device only sends packets via the interface of an etherchannel to the passive VSS switch, the mac address entry is lost in mac address table.If a ping from a source is via the active 4500x it works. If...

I think we might have got exactly the same problem.This is my theory:- The switches are connected via etherchannels- If you could follow the interface which is followed within the etherchannel, I think the source client is coming in on the first 4500...