OWA and OutlookAnywhere with DNS Round Robin

[ClayPerrine]

All,
I have a test environment setup with Exchange 2010. We will have two sites running Exchange, and DAGs will keep the mailboxes available if we lose one site.

The problem I have is that I setup the two client access servers in each site with a NLB address, then in DNS I enter both as the same name. Theoretically DNS should round robin the two NLB addresses, and connect to the CAS servers.

What happens is that OWA seems to sometimes switch servers,even after logon. And Outlook Anywhere will time out after authentication. If I take one of the two entries out for the DNS round robin, it works with no issues.

Wireshark shows the 3 way handshake failing because DNS returns the other server.

Any ideas on how I can load balance servers in two sites?

Thanks in Advance.

 

[sixteamparlay]

Try setting affinity to on for the NLB so when the nlb chooses a server to send it to that client always uses the same server for that session

 

[ClayPerrine]

Tried that.. single affinity is already on.

 

[ShackDaddy]

What's the TTL on the DNS records that round-robin is returning? It could be that things are hosing up because the record expires and a new DNS query ends up returning the other host IP first. Although it seems like affinity should take care of that.

When you use NLB, you aren't supposed to use RR-DNS are you? I thought you were supposed to point everyone at the NLB shared IP and the servers would balance on their own. Maybe you are messing it up by adding the RR component. It's been quite a few years since I set this sort of thing up, but I know I was doing NLB balancing without using DNS to do it.

Dave Shackelford MVP
ThirdTier.net
TrainSignal.com

 

[58sniper]

I'm with Dave. What's the need for that?

Pat Richard MVP
Plan for performance, and capacity takes care of itself. Plan for capacity, and suffer poor performance.

http://www.ucblogs.net/blogs/exchange/

 

[xmsre]

Within NLB, you have affinity. In round robin, you don't. Therein lies the problem.

XMSRE