Hi There, I have setup 2 AD server, DNS setup on both replicating each others, 1 domain. AD1.testing.com 192.168.1.1 AD2.testing.com 192.168.1.2 when I ping testing.com ==> reply is from 192.168.1.2 Primary Dns on Xp is 192.168.1.1 Client is configure AD1.testing.com IP as Primary DNS and AD1.testing.com secondary DNS (search order). Both AD are in the same network. But when I ping from client "testing.com", AD2 replies instead of AD1. Why? If I down AD2.testing.com. ==> request timeout when I ping testing.com. I thought AD1.testing.com should reply when AD2.testing.com is down. Why? Please advise. Thanks Daniel.K