I have three Windows Web Server 2008 SP2 machines on a 10.100.20/24 subnet. I need to setup a persistent routing rule so that outgoing traffic to the same subnet goes through a hardware load balancing device.
In Server 2003 it is as simple as adding a persistent route using the command:
route add -p 10.100.20.0 mask 255.255.255.0 10.100.20.157
In server 2008 that same command does add a similar persistent route, but the system basically ignores it even though it has a lower metric than the default record.
Here is the Server 2008 output from route print
:
IPv4 Route Table
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.100.20.157 10.100.20.178 276
10.100.20.0 255.255.255.0 On-link 10.100.20.178 276
10.100.20.0 255.255.255.0 10.100.20.157 10.100.20.178 21
10.100.20.178 255.255.255.255 On-link 10.100.20.178 276
10.100.20.179 255.255.255.255 On-link 10.100.20.178 276
10.100.20.255 255.255.255.255 On-link 10.100.20.178 276
127.0.0.0 255.0.0.0 On-link 127.0.0.1 306
127.0.0.1 255.255.255.255 On-link 127.0.0.1 306
127.255.255.255 255.255.255.255 On-link 127.0.0.1 306
224.0.0.0 240.0.0.0 On-link 127.0.0.1 306
224.0.0.0 240.0.0.0 On-link 10.100.20.178 276
255.255.255.255 255.255.255.255 On-link 127.0.0.1 306
255.255.255.255 255.255.255.255 On-link 10.100.20.178 276
Persistent Routes:
Network Address Netmask Gateway Address Metric
10.100.20.0 255.255.255.0 10.100.20.157 1
0.0.0.0 0.0.0.0 10.100.20.157 Default
To illustrate the problem, here is the output from a trace-route in Server 2008:
Tracing route to 10.100.20.1 over a maximum of 30 hops
1) <1 ms <1 ms <1 ms 10.100.20.1
Trace complete.
As you can see, the rule with the lower metric of 21 is ignored and the route goes directly to the machine on the 10.100.20/24 subnet. The routing should have gone through 10.100.20.157 before going on to 10.100.20.1. In Server 2003 this works correctly, but Server 2008 seems to ignore the rule with the lower metric. If I manually remove the default route so that my custom routing record is the only one for 10.100.20.0, then it is properly routed through the load balancing machine.
I've worked with Microsoft tech support and their proposed solution is to set the NIC to ignore all the default routing records and add every routing rule as a persistent route. I'm having trouble manually setting up all the rules to work properly, but I can work that out with Microsoft.
If there is a way to actually get Server 2008 to adhere to the metric rules, or script something to handle an event every time the TCP stack is initialized to remove the default route, or edit the registry to remove the default route when TCP initializes, any one of those solutions would be better in my opinion.
Best Answer
I think if the 10.100.20.0/24 network is directly connected, the server is going to ignore the route table and just use that link regardless of the metric.