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Load Balancer best practice for CAS internalurl

Posted on 2014-03-31
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Last Modified: 2014-04-04
I'd like to know what the community thinks is the best practice when you have multiple CAS servers behind a load balancer in an internet facing site.  Should the internalurl of the cas point to the servername or the private name of the internal VIP?  Microsoft says you should use the server name.  I have also seen posts and blogs contradict this and use the internal vip for the internalurl.

example:  

https://servername.internaldomainname/ews/exchange.asmx 

or

https://vip.domainname/ews/exchange.asmx (vip contains multiple CAS servers)


Any thoughts and comments are appreciated.
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Question by:mkllpit
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Expert Comment

by:Md. Mojahid
ID: 39968391
Load balancing recommendation.
1.Hardware Load Balancing
2.Integrated "is alive" monitoring recommended
3.Fixing of MAPI and direcotry endpoint ports
4.Create cAS Array and load-balace selected or all CAS in a site
5.Clinet IP affinity or cookie-based authentication where appropriate
NOt Recommended

1.DNS Round Robin
2.Windows Network Load Balacing
3.Do not load-balance cross-site,create two arrays instead and load-balance separately


Why Not Windows NLB?

Issues with WNLB

Switch/Port flooding in Unicast mode
NAT/Source IP pool
Scalbitlty over 8 nodes
Service awareness
Not support with Windows Failover Clustering
Add/remove single node causes all clients to reconnect
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Author Comment

by:mkllpit
ID: 39969114
Appreciate the response.  But that wasn't the question I was asking.
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Accepted Solution

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Simon Butler (Sembee) earned 500 total points
ID: 39970676
Personally I use the same host name inside and outside for Exchange, and then have it resolve to the load balancer internally. That way I get a consistent result everywhere.

If I have a problem, or want to do troubleshooting, then hosts files on the test machine do the job. I also usually put a host file on every Exchange server so that the relevant URLs resolve back to itself, again that helps with working in ECP.

I don't use the server name anywhere.

However it does depend where the load balancer is.
If you are doing a NAT to the load balancer, so it is inside, then the above works very well and I would consider that best practise.
If the load balancer is outside (so ONLY has an external IP address) then I don't want traffic going out to come back in, so it would be routed directly to the servers. However I wouldn't deploy a load balancer like that, as the bulk of the traffic (and reason for having them is internal traffic).

I am a JetNexus certified installer btw.

Simon.
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Author Comment

by:mkllpit
ID: 39976461
Thanks Simon!  When I added an entry on the local host file for the server itself and I ping the server locally it resolves to the IPv6 address.  Is that normal?

Another followup.  We had someone recommend using http instead of https: for the internalurl since its internal communication only.  I don't know if I am comfortable with that philosophy.  Anyone else out there use http instead of https and why would you?  This person said it would save us on the amount of SAN names on our cert as we have the servernames in the cert.

Ex  http://servername.internaldomainname/ews/exchange.asmx
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LVL 63

Expert Comment

by:Simon Butler (Sembee)
ID: 39977508
The server name itself coming back as IPv6 is normal. However you wouldn't normally put the server's own name through the load balancer, but the common name.

Therefore it is the common name that you want to resolve to the server itself.

As for the argument about SANs - from November 2015 (And any certificates that expire after that date) you cannot put internal domain names on to the certificate. I don't use the server's real name anywhere in the deployment - it is all the common name, therefore I can use HTTPS everywhere.

Simon.
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Author Comment

by:mkllpit
ID: 39977808
Simon,

So in the hosts file I would put the IP of the server and resolve it to the common name?  or the IP of the VIP and resolve to the server?  Just want to make sure I have this right
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LVL 63

Expert Comment

by:Simon Butler (Sembee)
ID: 39978379
You want the common name to resolve to the server.
The idea being that you are not using the load balancer at all to run things on the server (like ECP etc).

Simon.
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Author Comment

by:mkllpit
ID: 39978382
Great.  Thanks again Simon!
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Author Closing Comment

by:mkllpit
ID: 39978390
As always... Simon is one of the best resources for Exchange questions!  Glad he is available to answer these types of scenarios!
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