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SLow outlook connection to exchange in an NLB and CAS array

Hello,

Here is our configuration:

2 x Exchange 2010 servers running CAS & HT roles configured as a cas array
2 x Exchange 2010 servers running Mailbox roles only
Active directory domain domain.com (split scope)
Windows NLB configured using unicast

We have the cas array name and NLB configured both as cas.domain.com so pinging cas.domain.com resolved to the VIP of the NLB internally.

Outlook Anywhere and OWA clients connect to mail.domain.com so not the same name as cas array name

We have been seeing slow connections to outlook on the LAN whereby outlook is opened and it takes about a minute to connect to exchange - it will just sit there with connecting to exchange server. It does however get there in the end.

My worry is that the cas name is configured to use a name that is externally resolveable even though we have no external dns record for it and the external users connect to mail.domain.com I have been reading that this is not recommened practice?

Is someone able to verfy our configuration or suggest any troubleshooting metholds

Thanks!
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vmdude
Asked:
vmdude
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1 Solution
 
Simon Butler (Sembee)ConsultantCommented:
After Outlook has connected, is it using TCP or HTTPS? It sounds like somethign is timing out.
Outlook shouldnt use the Outlook Anywhere configuration unless it cannot connect to the Mailbox Server on CAS Array address.

If you bypass the NLB solution, and point the CAS array directly at one of the CAS role holders, does that improve matters?

Simon.
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vmdudeAuthor Commented:
Thanks Simon I'll give it a go and post my results.

As a side note we do seem to be having some underlying network issues which are currently under investigation by the network team which may or amy not be a red herring.
Whatever happens I'll post back here shortly
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vmdudeAuthor Commented:
Everything seems to be connected using HTTPS rather that TCP which I think is the issue. If I disable Outlook Anywhere then I can't connect so I think you have hit the nail on the head!

How can I bypass the NLB and point the array at one of the CAS servers? Is it simply changing the DNS entry for cas.domain.com to go to the a CAS server of my choosing?
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Simon Butler (Sembee)ConsultantCommented:
Yes, just change the DNS entry for the CAS Array host name and test. Hopefully you followed best practises and adjusted the TTL time down on that entry so the change is effective immediately.

The connection delay is the Outlook Anywhere failover time.

Simon.
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vmdudeAuthor Commented:
Thanks. In the end I added a host entry for one of the clients. Connected instantly to TCP/IP so the NLB is the problem. I'll need to double check the config!
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vmdudeAuthor Commented:
Ok so it looks like the problem is down to WNLB not working corrctly over unicast.
We have a VMware environment and everything I'm reading is pointing me to be using multicast. However the network team do not want me to use multicast for some reason.

Is it just me of does WNLB not really suited for load balancing exchange servers? I think we will go down the hardware load balanced solution. That said can anyone recommend any good ones?

Thanks
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Simon Butler (Sembee)ConsultantCommented:
The exchange team no longer recommend the use of WNLB.
http://www.stevieg.org/2010/11/exchange-team-no-longer-recommend-windows-nlb-for-client-access-server-load-balancing/

The main product of choice for Exchange load balancing is Kemp. They do a VM version as well.

Simon.
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vmdudeAuthor Commented:
The Winddows NLB was to blame. We are going to use a hardware load balancer to balance the traffic between cas servers
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