HiAll,I have a question regarding CAS NLB in exchange 2007.what is best recommandation for NIC CARD, one or two lan card and why ? with TWO NIC the ip address should same with other NIC which is not a part of NLB?THANKS,

You can find a good description about this topic athttp://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part2.html

Thanks for comment In this article Hennrik take two lan card. and i have also two lan card in production environment. but i have a doubt why we need two lan card, i mean its little confusing for mail routing because some time mail went with one NIC ip and some time with other. that exactlly happening with me. i haveFOUR boxes for exchange 2007 two boxes for active passive mailbox role and two for hub+CAS role.

The answer depends on the NLBconfiguration - unicast versus multicast.http://technet.microsoft.com/en-us/library/cc782694.aspx...Network Load Balancing modifies the MAC address of all cluster hosts to be identical, cluster hosts cannot communicate directly with one another when using unicast. When peer-to-peer communication is required between cluster hosts, include an additional network adapter or select multicast mode. ....Another good article ishttp://blogs.technet.com/clint_huffman/archive/2007/10/08/an-optimal-network-load-balancing-nlb-configuration.aspx