Win2000 TCP/IP route table, unwanted update on LAN fail

[Diarmuid]

I have searched several websites (incl Microsoft) but have been unable to find a solution to this problem. Any help you can give would be much appreciated - if I find the answer elsewhere I'll update this site!

Setup
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A multihommed server running Windows 2000 Server with NIC_1 for LAN_1 and NIC_2 for LAN_2. LAN_1 is for user and management traffic only, LAN_2 is to be used for embedded call-processing traffic only. There should be no traffic between LAN_1 and LAN_2.

A default gateway is setup on LAN_1 for access to the internet. The route table is setup so that traffic is routed to LAN_1 or LAN_2 according to the destination IP address.

Problem
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When both LANs are up, traffic is routed correctly. However if LAN_2 fails, Windows automatically updates the route table to remove all routing to LAN_2.

Actual Result
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All traffic now defaults to LAN_1. LAN_1 is suddenly flooded with datagrams that it cannot route.

Desired Result
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The datagrams destined for LAN_2 are eaten by the server.


Note
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VxWorks OS does not automatically remove entries from the route table if a LAN fails so this seems to be a Windows OS feature.
Even static persistant routes are removed from the routing table on LAN failure.

 

[PAGEME1000]

I have heard of a problem with multiple DNS servers in windows 2k...Microsoft have noted it will not be fixed in win2k but we will have to upgrade to XP where it has already been fixed....typical solution from a provider and we are yet to test it but by all accounts the seem to have done some extra work on the networking component....might be worth a try if you have XP lying around ;-)