Outlook clients loose connectivity after database failover in DAG exchange 2010

I am currently running exchange 2010 latest SP and updates.

I have 2 CAS/HUB servers in an WNLB configured with a casarray : array01.domain.com
I have 2 other servers with CAS/HUB/MBX roles installed.

there is only one site the default-first-site.  and all exchange servers are in the same site datacenter and subnet.

I currently have 5 databases each with approx. 50 users.  The RPCCLient access server
on all databases is set to the FQDN of the Casarray.

the cas array has only the 2 cas/hub servers not the mbx with the cas/hub roles aswell for obvious reasons, cant be done in a dAG.

the issue I have is when I failover the databases to the secondary server in the DAG, none of the outlook clients can connect or it is extremely slow.

could it be possible that even though the CASarray is configured they are not connecting to one of the servers in the array ? would the cas roles on the MBX servers interfere ?

also the DAG network runs over the same as the MAPI.
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Jamie McKillopConnect With a Mentor IT ManagerCommented:
All those URLs that point directly at a cas server need to point to a URL that points to your casarray IP. You can switch it to your external URL if you are able to hit that URL internally.

Jamie McKillopIT ManagerCommented:

First, you should remove the CAS role from the DAG members. You can only have one CAS array per site. If you want to want to use the CAS role on the DAG members, you need a hardware load balancer and have all CAS members behind that load balancer.

Check the settings in Outlook and see what server name they are point at. They should be pointed at the CAS array name.

mndthegap1Author Commented:
could this be part of the problem having the mbx servers also have the cas role, and not be part of the cas array ?

I thought if a casarray was configured and assigned to the DB's then outlook would only use the cas servers within the array. is that not true ?

can and will outlook still connect to one of the other cas servers ?
Jamie McKillopIT ManagerCommented:
Outlook should only connect to the casarray, however, that assumes that the casarray was configured properly before the Outlook clients connected. If you setup the casarray after the fact, Outlook would use one of the CAS servers directly until manually updated. This is why I suggest you verify the server setting in Outlook to ensure it points to the casarray. Also, make sure you verify that your web services also point to the casarray and not directly at a CAS server.

mndthegap1Author Commented:
Okay I tested the auto config like you asked. and seems to be hitting  the casarray.
I did notice thought that the internal URLs poing to one of the cas servers that is not part of the casarray and has all 3 roles assigned.

Internal OWA URL: https:// cas01.domain.com/owa  <- cas server with just cas/hub part of array
external OWA URL: https://mail.domain.com/owa <- external URL for owa/activesync, etc

Protocal: Exchange RPC
server: casarray.domain.com
availability service URL: https://Cas03,domain.com/ews/exchange.asmx <- one of the MBX servers that has the cas role assigned and not part of the array.

OOF URL: https://Cas03,domain.com/ews/exchange.asmx <- one of the MBX servers that has the cas role assigned and not part of the array.

OAB URL: https://Cas03,domain.com/oab <- one of the MBX servers that has the cas role assigned and not part of the array.

ECP URL: https://Cas03,domain.com/ecp <- one of the MBX servers that has the cas role assigned and not part of the array.

PRotacol =HTTP:
server mail.domain.com  <- external URL

availability service URL: https://maildomain.com/ews/exchange.asmx
OOF URL: https://mail.domain.com/ews/exchange.asmx
OAB URL: https://mail.domain.com/oab

so this looks correct ? it does find the cas array for the RPC.
the only thing is the internal URL should also be pointing to the external URL Mail.domain.com  correct ?
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