I have installed two hub cas servers with exchange 2007 sp1. IP configuration for both servers are hub-srv1 - NIC-10.0.240.166/27 NIC2-172.16.0.1Hub-srv -NIC1 -10.0.240.167/27 NIC2-172.16.0.2NLB IP - 10.0.240.175/27nlb name - mail.domain.comIP address for my server farm is 10.0.240.160/27all my clients are on diffrent VLANnow after configuring the NLB refering to article in exchangeorg..I am not able to ping the nlb ip from the client machines

Your firewall may not be allowing ICMP. Have you set up the proper port rules for NLB and then tried to telnet to these ports? Here's the typical port rules that I use for a standard CAS NLB: http://www.shudnow.net/images/HyperVNLB08.jpg Any chance you're running on Hyper-V? If so, check out my article here: http://www.shudnow.net/2008/09/12/exchange-2007-unicast-nlb-issue-on-hyper-v/ MVP | MCSE:M | MCITP: Enterprise Messaging Administrator | MCTS: OCS + Voice Specialization | http://www.shudnow.net

Network Load Balancing can be configured with Unicast and Multicast. If you use Multicast, you might have to do some additional configuration on your router or switch. Each server’s NLB network card operating in multicast mode has two MAC addresses (the original one and the virtual one for the cluster), which causes some problems on its own. Most routers reject the ARP replies sent by hosts in the cluster, since the router sees the response to the ARP request that contains a unicast IP address with a multicast MAC address. The router considers this to be invalid and rejects the update to the ARP table. On a Cisco router you would need to add this command: # Create a static ARP entry for Cisco IOS arp 10.0.240.175 03af.789e.cd4a ARPA IP address is your NLB address; MAC address here is bogus: add yours. Jon-Alfred Smith MCTS: Messaging MCSE: S+M

Setup two servers running Windows Server 2003 with two NICs in each server Install Exchange Server2007 Hub Transport and Client Access Service (CAS) on each server Configure one NIC for the Network Load Balance cluster and setup the other NIC in a separate network so it can be managed through that IP address Configure NLB with Unicast and even load balancing Setup the port rules: Port 25 to 25 for both TCP and UDP and select the radio button to disable this port range (this will exclude port 25 from being listed to using the virtual IP address of the NLB cluster, but still allow the individual server IPs to still listen to port 25) Port 465 to 465 for both TCP and UDP and selected the radio button to disable this port range Port 80 to 80 for both TCP and UDP and set affinity to none (I recommend "none" so you can easily test and verify that it works) Port 587 to 587 for both TCP and UDP, affinity none (this is for the client SMTP receive connector) Port 443 to 443 for both TCP and UDP, affinity none Port 110 to 110 for both TCP and UDP, affinity none Port 993 to 993 for both TCP and UDP, affinity none Port 143 to 143 for both TCP and UDP, affinity none Port 995 to 995 for both TCP and UDP, affinity none With affinity set to none, you can more readily test the CAS (after updating the web pages to show which server is actually responding) and verify that the load is being shared. You can also test to make sure the NLB cluster does not respond to SMTP on port 25, which it shouldn't if you set it right, and verify that each server does respond to SMTP as an individual server name. You can configure protocol logging for the other protocols and telnet to the ports using the NLB IP address to see if they are loading balancing like they should. You can also use the NLB IP for the testing by sending and receiving messages and checking the message tracking logs to see that the traffic was being balanced. It all workedgreat one :http://social.technet.microsoft.com/Forums/en-US/exchangesvravailabilityandisasterrecovery/thread/ba52385d-b0ce-42f6-8657-4fe18ee45d6bhttp://www.msexchange.org/articles_tutorials/exchange-server-2007/planning-architecture/load-balancing-exchange-2007-sp1-hub-transport-servers-windows-network-load-balancing-technology-part1.htmlhttp://exchangeserverinfo.com/2008/03/20/network-load-balance-for-hub--cas--exchange-2007.aspxregardsSyed Arsalan. syed.arsalan