CentOS - Oct 2007 - multipath using 2 NICs (or HBA?)

I'm told that we cannot do Multipath I/O on our iSCSI SAN on RHEL
with 2 network cards.  I could use 1 network card, but need an HBA.
Is this true?  Do I need an HBA, or can I do Multipath using 2 NICs?
We're running RHEL 4 and CentOS 4 and 5 servers on this network.

I have been reading through the device-mapper documentation, but I
have not found anything (unless I'm not clear on what they're saying).
Eventually I will give it a try but I haven't had the time to fiddle so far.

Thanks,
Scott