Default Gateway Question

[Todd]

Hopefully someone can explain to me how something is
working. I have a Windows 2000 Advanced Server (not that
makes a difference) and its Default Gateway IP address is
the same as the Client IP address. Example: IP of the
server is 10.x.x.65 and the default gateway is 10.x.x.65.
This server is operating normally and can browse both
inside and outside of the network. How does this server
know to send the traffic to the correct gateway when the
gateway IP isn't defined on the server?

 

[Michael Johnston [MSFT]]

This shouldn't work under normal circumstances. There are a few cases though were it may. If the server is running some sort
of routing protocol that allows it to learn routes this may get the server around this. RIP, OSPF or IGMP could get the server a
route. Another case where this can work is if there is network hardware device that translates the ARP messages for off subnet
devices. What happens is that since the DG of this server is it's own IP, it will ARP for the IP address of the destination even if
this destination is off subnet. There are special devices out there that will proxy ARP this and allow connectivity offsubnet. This
is very uncommon though. Check the actual routing table on the system to see if it actually has a default gateway. Run "route
print" at a command prompt and look for the 0.0.0.0 entry. If the box is running RRAS, open the RRAS MMC. Go to IPRouting>
Static Routes. Right Click on Static Route and choose Show IP Routing Table.

Thank you,
Mike Johnston
Microsoft Network Support
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