Unity Connection load sharing and redundancy using IMAP

Answered Question
Jun 10th, 2010

So the documentation is a little unclear when it comes to making IMAP clients work with load sharing/balancing and redundancy in Unity Connection (we're talking versions 7 and 8 of CUC).

Say we have two servers each having the host name hostA and hostB, and a bunch of Outlook clients with IMAP accounts on them.

While I understand the recommended design is to home all IMAP clients to one server, I would like to permit automatic failover to the other CUC server in the event of failure. Other than using a load balancer or dynamic DNS, is there a way to do this? The round robin DNS instructions are a little hazy and contradictory. How are people doing this today? I'm open to load sharing if that is what we need to do.

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Correct Answer by William Bell about 6 years 7 months ago

You create a common DNS name that points to the IMAP service so:

DNS A record hosta.yoursite.com   is 10.10.10.10

DNS A record hostb.yoursite.com   is 10.10.10.11

Then you have a DNS record like so:

cucimap.yoursite.com. IN A 10.10.10.10

cucimap.yoursite.com.  IN A 10.10.10.11

Your clients are configured to use IMAP host cucimap.yoursite.com.  DNS client will resolve the name and cache two IP addresses.  The idea is that client will connect to secondary host if primary fails.  The issue is that clients will often need to reconnect since this method doesn't support a dynamic failover.  Like SLB would.

The concept is similar to google.com (do a nslookup on google.com and you'll see what I am referring to).

HTH.

Regards,
Bill

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Correct Answer
William Bell Thu, 06/10/2010 - 17:21

You create a common DNS name that points to the IMAP service so:

DNS A record hosta.yoursite.com   is 10.10.10.10

DNS A record hostb.yoursite.com   is 10.10.10.11

Then you have a DNS record like so:

cucimap.yoursite.com. IN A 10.10.10.10

cucimap.yoursite.com.  IN A 10.10.10.11

Your clients are configured to use IMAP host cucimap.yoursite.com.  DNS client will resolve the name and cache two IP addresses.  The idea is that client will connect to secondary host if primary fails.  The issue is that clients will often need to reconnect since this method doesn't support a dynamic failover.  Like SLB would.

The concept is similar to google.com (do a nslookup on google.com and you'll see what I am referring to).

HTH.

Regards,
Bill

Please remember to rate helpful posts.

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