I'm not 100% sure whether this is an Exchange issue, or something on our network, but either way it is very strange...
I have a 3com powered network, 4x 4200's, and a 4400 which is the central one. I've disabled Broadcast Storm Control (which I thought might be a problem) and the Multicast Filter on all these.
My problem is, I run a constant ping (as I'm trying to debug this problem) from my machine to 3 of our servers, the Exchange server, the DC and SQL server and a NetApp Filer. The trouble is, I'll lose approximately 5-10% of these pings over the course of the day, for no particular reason. One of the machines, usually the Exchange or Filer, will just drop all pings from my machine. However it won't have dropped pings from all machines. I run the same ping from the DC and it'll run fine during my outage, although it itself will have problems when I don't.
Quite an aggravating problem, as I have no idea how to trouble shoot this. The NIC's on all servers are fine, the Exchange box is an identical hardware build to the DC. The only errors I get in the Event Logs are that Exchange losses connectivity to the DC and GC occasionally.
The bizarre thing is when I look at the ARP tables on my machine. During the ping outage, which usually last about 5 minutes, if i bring up the ARP tables, the IP of the failing machine is identical to the IP of the gateway box (PIX 515e). If I clear the ARP cache, it will immediately regain connection to the failing machine.
What I _think_ is happening, is that 1 ping is getting dropped, or failing, and so the client machine asks the gateway what route to take. Somewhere the client machine decides that the route to the host machine is through the gateway, which is where it fails. But again, I don't know how to trouble shoot or start to fix this problem. Our office is too small to even start thinking about VLAN's (4 servers, 50 users). However I need to get this fixed as I need to launch the Exchange server into production in the next few weeks.
Any help please?
Chris K