I have a strange situation that I think others in this group could probably clarify for me. I have two old Bay Networks / Nortel Accelar 1200 switches, A and B. Switch B uplinks to A, which uplinks in turn to a Netgear switch which then connects to a firewall. When I plug Computer One to switch B or switch A directly, the computer works but unreliably. Occasionally incoming packets are getting dropped (maybe one in six). Computer One has a single Netgear 10/100 ethernet card in it.
If I take the same Computer One and plug it to a Netgear hub, and then uplink that hub to either switch A or switch B, now the Computer One works very reliably, both fast and no dropped packets at all.
Does anyone have an explanation as to why such a behavior would happen? The sniffer trace when run from the Computer One clearly shows missing packets, as compared to the sniffer trace taken from the firewall on the subnet outbound from the firewall to the switch A / B complex. I assume the problem is at the ethernet level, which unfortunately the trace doesn't show, except for layer 2 / ARP. I suppose there could be another computer doing man-in-the-middle attacks and stealing packets using Computer One's ethernet address, but I'm hoping to find a simpler explanation before going off on a wild goose chase for a hacker.