Hi,I have a question related to the architecture of CAS NLB. I have three sites and each has two CAS servers running NLB and only one of them is internet facing which is made externally available usig ISA 2006. There is an article on TechNet called "Understanding Proxying and Redirection"that has my exact scenario and pointsoutwhat valuestouse forthe Internal URLs for various virtual directories which has created a lot of confusion for me but does not explain why it recommends that. Here are their recommendations: /OWA should always point to https://computername/OWA for every CAS server. Why the server name and why not NLB hostname? /OAB should point to https://computername/OAB for internet facing but to https://NLBName/OAB for the non-internet facing. Why should the two be different? The rest including ActiveSync, UnifiedMessaging, and EWS have the same setup as OAB where the internet facing CAS internal URL points to the server name whereas the non-internet facing CAS internal URL points to the NLB hostname. This make no sense to me. Any help with underdtanding this would be very helpful.Thanks,Anupam Agarwal

hi,http://social.technet.microsoft.com/forums/en-US/exchangesvrdeploy/thread/067029c2-08a6-4d86-a6c9-ede3fa9996de/http://social.technet.microsoft.com/Forums/en-US/exchangesvravailabilityandisasterrecovery/thread/6525873b-65ed-4da1-8bb7-54fa032692daregards,Exchange - MVP | www.cozumpark.com | www.mumincicek.com

Sorry but neither post really answers the questions I am asking. One post says that two CAS servers cannot have the same internal URL. According to the TechNet article, that is not true. CAS servers serving as nodes for the same NLB use NLB hostname for internal URL and therefor are bound to have the same URL. So that suggestion is in conflict with TechNet recommendation. The second post talks about load balancing smtp which is not what my question is about.Any help with regard to understanding internal URLs in an NLB as described in the TechNet article would be appreciated.Thanks.

Thanks. I am very familiar with how the NLB works andthere is no issue with NLB in this case. The question is about providing values to the internal URL for various virtual directories - namely OAB, OWA, Microsoft-Server-ActiveSync, UnifiedCommunications, and EWB. Below is a cut and paste from the Technet acticle:---------------------------------------------------------------------------------------------------------------------- Proxying with Network Load Balancing In an organization that has multiple ActiveDirectorysites and multiple Client Access servers in each site, you can use Network Load Balancing (NLB) to distributetraffic among the Client Access servers in each site for failover redundancy. We do not support including Client Access servers from different ActiveDirectorysites within the same load balancing array. You can deploy NLB in an Internet-facing ActiveDirectorysite and in a non-Internet-facing ActiveDirectory site. The following figure illustrates two ActiveDirectory sites that implement NLB. Proxying in an organization that uses NLB The following table lists the settings for the virtual directories that are on the Client Access servers CAS-01 and CAS-02 for the Internet-facing ActiveDirectorysite www.contoso.com. Virtual directory settings for Internet-facing Client Access servers in an organization that uses NLB Virtual directory InternalURL setting /OWA https://computername/OWA /OAB https://computername/OAB /UnifiedMessaging https://computername/UnifiedMessaging /Microsoft-Server-ActiveSync https://computername/Microsoft-Server-ActiveSync /EWS https://computername/EWS The non-Internet-facing ActiveDirectorysite has three servers: CAS-03, CAS-04, and CAS-05. The following table lists the settings for the virtual directories for all three servers. Virtual directory settings for non-Internet-facing Client Access servers in an organization that uses NLB Virtual directory InternalURL setting /OWA https://computername/OWA /OAB https://NLBname/OAB /UnifiedMessaging https://NLBname/UnifiedMessaging /Microsoft-Server-ActiveSync https://NLBname/Microsoft-Server-ActiveSync /EWS https://NLBname/EWS -----------------------------------------------------------------------------------I just would like to underdtand why we are using server names for the CAS NLB thatis in the internet facing site versus NLB names for CAS NLB in thenon-internet facing site.Thanks,Anupam Agarwal

Hi,The article below may be helpful to youEWS CAS to CAS Request Proxying http://msexchangeteam.com/archive/2008/07/18/449289.aspxRegards,Xiu

I have see this article also. It explains why NLBBypassURL is important for EWS but does not say anything abuut the internal URL values proposed by the TechNet article above.