Windows XP/2000 workstation in LAN-LAN routing environment

[J.H]

Hi everyone,

I have very strange situation that:

Currently we have 2 network, each network has its own LAN router

LAN router 1: 10.10.10.1/255.255.255.0
Static route added: 192.168.0.0/24 --> 10.10.10.2/255.255.255.0
one ServerC in 10.10.10.10/24

LAN router 2:
InterfaceA: 10.10.10.2/255.255.255.0
InterfaceB: 192.168.0.1/24
routing and remote access configured, add RIP, IGMP onto InterfaceB
one ServerD in 192.168.0.2/24

Testing:
Scenario1: from ServerC can do any network access to serverD OK good!!
Active Route table of ServerC has:
192.168.0.2 255.255.255.255 10.10.10.2

Scenario2: from ServerD can also do any network access to serverC OK good!!
Active Route table of ServerD has no entry of 10.10.10.0/24 network OK I
don't care this!

Scenario3:
if I install ISA server firewall on 10.10.10.1, the Scenario1's active route
table as above
will never update with that line. (of course after I install ISA server, I
managed to get ServerC & ServerD
can do any network access each other).

If I uninstall ISA server firewall, the Scenario1's active route table will
appear again. Anyone knowing why?
Does the ISA server firewall blocking some subnet mask broadcast traffic
(255.255.255.255)?

Anyone input will be greatly appreciated!

J.H