DAG groups and multiple gateways

Hi all,

We use Exchange 2010 SP2 and our setup is virtualized in vmware.  Right now all of our mailbox servers have one nic, but I want to add a second one that will be used for the DAG network.  Two quick questions:

1.  Should I set a default gateway on the 2nd nic that will be used for the DAG network?  I got a warning message when I first tried to enter a default gateway and I started thinking that maybe I didn't need it anyway, if the DAG traffic stayed on the same subnet.

2.  Should the witness server have a nic attached to the DAG network as well?

Any help is appreciated, thanks.