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I've had a route in Windows Server 2008 R2 RRAS that's been working for a long time, which is 192.168.100.0/24.

The network on the other side of that link recently added a new subnet, 192.168.101.0/24

So, naturally I thought to myself, I would just modify the existing route to the following:

192.168.100.0/23

But no go. Nothing on the new subnet goes anywhere.

But, if I make the following setup:

192.168.101.0/24

Which is effectively the same route as above, just more verbose, works perfectly.

I don't mind having the two routes, but I'd really like to know why it's nessesary. Any ideas?

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If you look at the route table with route print does it show things correctly when you have the /23 route? Does a traceroute show the traffic trying to leave the correct interface? – Zoredache Dec 12 '11 at 21:25
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Thar she blows: 192.168.100.0 255.255.254.0 192.168.161.106 - however, I see there is a realllllly old RIP route still hanging around that's for a much smaller range on the 192.168.101.0/24 network which will be taking precedence. Sometimes I just have brain farts all day. – Mark Henderson♦ Dec 12 '11 at 21:51
Post that as an answer and I'll give it the checkmark, I removed the RIP listener (forgot it was there), and now she's all good. – Mark Henderson♦ Dec 12 '11 at 21:54
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If you look at the route table with route print does it show things correctly when you have the /23 route? Does a traceroute show the traffic trying to leave the correct interface?

Some times what you see in the Windows GUI does not reflect what Windows is actually doing. I find that it is always best to double check from the command line.

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This put me on the right track - there were a bunch of old RIP routes that were smaller than the /23 route which were taking precedence. Got rid of the RIP listener and the RIP routes (they were redundant) and everything came good :) – Mark Henderson♦ Dec 12 '11 at 22:42
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