Description of problem:

In RHEV-M GUI, if we fill the Gateway setting the management network this address is used for the default route.

However, if we fill it for non-management networks, we are actually setting up source based routing by using special routing tables and ip rules to instruct the kernel to look at specific tables in the FIB for packets which have specific source-IP/interfaces. See: http://www.ovirt.org/Features/Multiple_Gateways

Our documentation in https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Virtualization/3.5/html/Administration_Guide/sect-Hosts_and_Networking.html (section 7.6.2. Editing Host Network Interfaces and Assigning Logical Networks to Hosts) does not mention this important detail. 

So people fill the gateway option for non management networks and expect that gateway to be the default route for the Host. But it is not since it's only valid for forwarding (not in use) or reply packets arriving from that Network (some conntrack magic here I suppose).

So I suggest we put a note in there to link some other part of the documentation or to explain these differences.

I haven't confirmed this in 3.6 but I suppose it's the same.

Cheers,
Germano