two exchange 2010 servers, two public IPs, and OWA set up

Posted on 2014-04-04
Medium Priority
Last Modified: 2014-04-15

I have two exchange servers in a DAG. Both have CAS, HUB, and MBX roles. The first is set up with a cert, OWA, DNS, and firewall rules allowing mail to flow between us and our smart host, as well as webmail and activesync. I have a second exchange server onto which I am going to install the wildcard cert from the first exchange server and then apply services to it.

I am looking for help / directions on setting up the second exchange server to functionally mirror the first. This is for availability if the first were down.

Can webmail.domain.com point to two different public IP addresses, with each going to a different exchange server in the domain through NAT on the firewall? Or, do I just manually NAT webmail.domain.com's IP address to the second server upon failure of the first (or have the rule ready but disabled and then simply enable it upon the first server failing)?

Should I enable rules for the second exchange server (mirrored from the first, typical exchange services) on the firewall or leave them disabled and enable as needed if the first server goes down?

My goal is to have mail flow and outlook/mobile connectivity on the second server should the first server go down. I have the DAG configured and have witnessed databases failover as they should. I also have a CAS array in place (which I will manually point to the second server if the first goes down). I am just unclear on the DNS, firewall, and OWA set up for the second server.

Thanks a lot for any help.
Question by:rpliner
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LVL 63

Expert Comment

by:Simon Butler (Sembee)
ID: 39979117
Personally I would give both hosts their own unique host name, and configure Exchange with that host name as appropriate.
Both hosts can appear in the MX records and if a failover event occurs, mail will continue to flow.
End users can be told the second URL and told to use it.
Although if you are happy to do the manual change for the CAS Array, why not a manual change for the NAT records?

DNS does not provide any kind of failover, so having both hosts in your DNS records isn't going to help - it is going to be pot luck which server a user hits.

If you want fully automated, then you will need a hardware load balancer.


Author Comment

ID: 39979179
I will go ahead and manually change the CAS array and the NAT to the second server.

My MX records point to spam soap, so if I point the public IP to the second server through NAT, and since spam soap is already configured to accept email from that public IP, I should be good there, correct?

I was also concerned about mobile devices since they are configured with webmail.domain.com as the server. That's why I was wondering how to configure OWA on the second server while keeping the URL the same so users wouldn't have to reconfigure their mobile device.

Thx so much again.
LVL 82

Expert Comment

by:David Johnson, CD, MVP
ID: 39979357
Without a load balancer or setting up high availability where the ip address point to is not a function of dns

internet -- load balancer -- server 1 -- HA storage group
                                           -- server 2 -- HA storage group
you can then fail server 1 or server 2 and things will just carry on.
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Author Comment

ID: 39979385
Thx David. No load balancer. I don't mind manual just don't want users having to change mobile devices. I don't control our DNS records (long story) but I'm looking into a 15 TTL on webmail and just changing that to the public IP of the second server. Then with firewall NAT public IP to second exchange private, and owa configured on the second, users shouldn't need to do anything on mobiles, I think???

Assisted Solution

rpliner earned 0 total points
ID: 39984302
I think I figured out the steps.

I have already set internal DNS TTL to 10 minutes. I am going to change the rpcclientaccessserver to the CAS array.

-MX records point to spam soap - leave alone

-External DNS points webmail to public IP - leave alone

-Internal DNS
-- point CAS to operational server
-- point webmail to operational server
-- point autodiscover to operational server

-- change rules (NAT private to public & public to private changed to reflect operational server's private IP)
-- change OWA, which has its own rule, to operational server's private IP
-- leave public IP as is
-- leave services as they are

I believe this should do it. MX stays the same since it points to Spam Soap. External DNS points webmail.domain.com to public IP which is configured on firewall, so leave that alone. Change internal DNS for CAS, webmail, and autodiscover to operational server. Go to firewall and change Exchange server NATs to private IP of operational server, leave public IP as is. Change OWA rule's private IP to that of the operational server, leave public as is.

If I do this, spam soap will recognize the public IP it is receiving email from for us as it is already configured. OWA will have the same public IP in external DNS so once the firewall NAT is reconfigured with the operational server's private IP, mobile devices will connect (internal DNS will have already been changed to the operational server).

The only other thing I can think of is correctly configuring OWA on the secondary server. Right now webmail.domain.com is only configured on the internal URL under Server Config>Client Access>OWA (default website)>properties>general tab, not external as is the primary server. So I think I need to enter webmail.domain.com into the external URL field. I see the wildcard cert on the secondary server, but no services have been assigned so I will need to mirror the services configured on the primary server. Once that is done, I believe webmail.domain.com will resolve to the secondary server and no cert issues will arise.

I realize the last paragraphs may be a bit convoluted but please let me know if this looks correct.

Author Comment

ID: 39992031
Is anyone available to quickly verify the procedure I entered above?

thanks a lot. going to test it this weekend.
LVL 63

Accepted Solution

Simon Butler (Sembee) earned 2000 total points
ID: 39992603
Yes, the plan sounds about right.
You just need to give Exchange enough time to replicate the changes, so if something doesn't work correctly immediately, just wait a few minutes.


Author Comment

ID: 39992675
thanks as usual, Simon.

Author Closing Comment

ID: 40001126
I chose my "plan" as part of the solution in case anyone found this and needed to do what I am doing. Simon pointed me in the right direction, as usual, so I awarded him points for that and for looking over the plan to verify that it should likely work.

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