It could be a few things:
1. make sure your nics are the ones you think they are. what you assume is eth0 could really be eth3. and they may not be consistent across both servers

2. Verify your vlans are setup right

3. This stands out to me: is all traffic on 172.16 on the same vlan? If possible you should get a separate switch for the iscsi traffic. I would use a crossover cable for the replication instead of a switch.
if you can't get another switch make a separate vlan for each subnet

4.************please tell me the picture is wrong, you have 172.16.1.101 on two different hosts.