Small network - big issues

[ArnaG420]

Hey guys.
I have quite strange problem. First I'll explain shortly before going to details.
I have 2 PCs having 2 adapters connected to 2 switches.
PC1 port 1 - 10.220.16.126
Port 2 - 10.220.17.126
PC2 port 1 - 10.220.16.127
Port 2 - 10.220.17.127

I can ping from both sides using first subnet (16) but I cannot ping PC2 through the second subnet (17) - I loose about 80% pings.

What's the most strange for me is this:
While I try to ping from PC3 (my laptop) I'm successful if I'm out of that network - connected to some higher level switch - to both PCs and both ports.
But once I connect to that switch and set up appropriate IP (10.220.xx.125) - I can ping both PCs in subnet 16 but I "can't" ping PC2 in subnet 17 (10.220.17.127) and I'm getting timeout in approx 80% pings, some of them make it through though...

What could be the reason that I can easily ping both PCs while I'm out of that network (connected to switch which is far away from the switch nearby PCs and in different subnet) but I'm getting so many timeouts while pinging PC2 while I'm in same subnet??

I exchanged the PC2 and reimage it- no help. I used another switch just to make sure and got exactly the same results - once I'm connected in the same subnet I can't stable ping PC2 repeatedly.

Thanks for any ideas.

[Matthew_Hum]

First off what switch are you using? What features/config? what else is going on? I don't quite understand your setup here, but I'll try based on what it sounds like.

It sounds like you are dual homing PCs onto different networks. what are the internal routing tables of the PCs? what about the metrics? how about the router config? it could be local routes with the same metric and one works while the other has a misconfiguration. that would cause intermittent issues.

If you are to rule out network causes of intermittent issues, I'd look for things like rate limiting or other COS mis-configurations.