I am trying to identify what is causing a huge number of OUT Discard (err) messages on my switches. I see these when I run “sh int counters errors”. I have 11 VLAN’s running on the network, and these errors occur in ports that I have trunked with no ACL. Almost all my ports are either access or trunks with ACL, but a few of them are trunks (dot1q). On the interfaces where I restrict VLAN or on the ports with just access enabled, I do not see these errors.
Is there a tool I can use to identify what is generating all these packets and or what VLAN they are coming from? If I can identify the culprit, I can identify the VLAN. I know I can use Wireshark to read what’s on the wire, but I’m not sure how use Wireshark to identify the VLAN and or the IP address(s) creating this “noise”.