TMG 2010 Internal Array Connection

Hi All,

My client environment have 2 TMG 2010 SP2 server Array.

Call it with A & B. A is Primary TMG server.

The condition is  server A can ping server B with production network & internal array network.

But server B cannot ping server A either with production network or internal array network.

All TMG services is running on both server.

TMG functionality is OK on both server. Both server can open TMG console.

If we create rule, rule will replicated to other server.

My question is,

Server B totally cannot communication with server A (based on ping test), but why TMG server work properly on both side?

Can anyone explain me what make this happen?

Thanks for your help :)

Best Regards,

Henry Stefanus