25 Server Network issue with 200 workstations 1

[Marc156]

History: We have a network of 25 servers including one Lotus Notes server on 192.168.1.132. We use a CISCO PIX for NAT. We are now with a new ISP provider on 3 T-1 Lines for the last week. Before this time we have not had a problem.
Problem: This server appears to be fine on the 192.168.1.132. Out of the 200 workstations about 10 - 20 a day loose connection with this server for about 3-5 minutes at a time. This will only happen to one workstation at a time.

Known: When the workstation can not connect, you can not ping the server (failed response)Yet this workstation can hit any server on the network including the gateway 192.168.1.1 and wins server 192.186.1.10
If you go to any other workstation on same network segment and ping the Notes server you get a good reply.

What I have done so far.
1. changed network cable on server.
2. Changed NIC card.
3. Editied Host file to point to server.
4. Confirmed all server settings
5. NBTSTAT -R

Still have same issue with no results.

Please I need your help for more ideas..

Thanks

Marc L
MCSE

 

[bcastner]

Remove all forwarding DNS entries from your DNS server, and then re-add them.

Make certain all clients point only to your local DNS server; it and only it should have an entry to resolve external DNS references through forwarding.

If the problem workstation clients are XP, it is almost certainly a DNS issue. The only other likely candidate is an autonegotiation failure. Be certain to set the XP clients appropriately: for hubs, 10 Half Duplex, for Switches 100 Full. Do not use the "Auto" setting.

It is possible the DHCP leases are expiring too soon, adjust the lease time on the PIX.