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Strange network activity on LAN


Currently have an issue since upgrading a corporate network.

The office was running single VLAN, and now has mutliple VLANs configured (most hosts are still on the single VLAN)  and will migrate soon into their respective vlans soon. I have a 4500X running in VSS acting as L3 SVI default gateways for a handful of VLANs. The 4500X has multiple PAgP port channels to 3 other L2 switches which are the edge ports (2x2960G and one existing 2950).

I have noticed that a few hosts/devices on a VLAN have all of a sudden stopped responding to pings for around a few minutes. But then I found out it wasnt the host/device going down, but the workstation pinging the host that was timing out the pings. Pings from another workstation showed the device as up.

Thought it was isolated, then it happened on another workstation with a different device later that day.

The other thing I noticed was that it didnt matter if the PC was on the local subnet or not.. I tested from a workstation from another office which was on a different subnet and still the pings dropped, but pings were up from another PC. Also I noticed that pings seemed to drop approx every 10 minutes, although I havent done enough testing to confirm this the same across the board with all devices.

So far it is just failry standard config. Port channels are PagP, desirable set on both sides of the port channel. 2 of the edge switches have load balancing on the port channel to src-dest-ip whist the old switch is src-mac. The 4500x is also src-dest-ip.

So far its too early to tell, but the devices are attached to the old switch (2950). The switch was in use earlier without any issues.

Any ideas or how best to troubleshoot? I plan on setting up some moniotoring of the subnet to work out exaclty whats going up/down.


Strange network activity on LAN

Anything showing in the switch logs (all switches)?

Check your Port channel interfaces to see if there are any errors?

Run some constant ping tests from device to device to see if there is a pattern to the packet loss.

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