In Exchange 2010 when setting up DAG groups it is best to have a dedicated NIC for your heartbeat/replication network. When doing this you do not want to put a gateway. Instead you should specifiy manually using the netsh command a route to your other server. Here is how it can be done.
show interfaces (use this command to determine what interface to use)
add route 10.0.1.0/8 “Internal” 10.0.0.5 (This command is pretty straightforward. You specifiy the network you are trying to connect to and the second IP listed here is the gateway that should be used)
To check that it was completed successfully you can review the routes.
netsh interface ipv4 show route
To delete the route
netsh interface ipv4 delete route 10.0.1.0/8 “Internal” 10.0.0.5