I have a test configuration using 2 MT v3.25 connected directly via 3 Ethernet ports which are bonded configured for balanced round robin mode.

In this test configuration, I have arp enabled for link monitoring. Running bandwidth test, the behaviour is as expected - each link carrying 33 Mbps of traffic and when one linked pulled out, the other 2 links carrying 45 Mbps traffic.

In the next test, the number of bonded links is reduced from 3 to 2. The bonded link no longer works. On further investigation, I could get the bonded link working if I disable link monitoring.

What am I missing or does arp link monitoring work only for 3 or more bonded link?