how many NICs for sync. replication with failover function over LAN?

Hello to everyone!

I am having a problem to make the failover function work.

I have installed open-e in a small test environment on two servers with a single client that runs Windows XP. Each of the servers has 2 network interface cards.

Is it true that I need 3 (or 4) NICs in each server in order to get synchronous replication with failover function? Is there another way to do it?
In the manual (Open-E_DSS_V6_Synchronous_ Volume_Replication_ with_Failover_over_ a_LAN.pdf) there is a separate NIC for the web GUI. And why do I need the auxiliary connection twice? This seems strange to me.

Thanks in advance!

Christian