[cisco-voip] Changing DNS entries in Call Manager 9.1.2.10000-28

Thu May 28 10:26:09 EDT 2015

We switched to IP addresses for our CUCM server entries and haven’t had any application problems. Jabber appears to use the hostnames set in the “UC Server” settings not the System->Server settings.  Windows accepts IP addresses in certificate Subject Alt Name attributes too.

We had an issue at one point where some of our phones briefly lost L3 access to DNS and CUCM briefly (no SRST). They were down for 10 minutes or so after the network came back. Seemed like they didn’t like that they had been unable to resolve the CUCM DNS entries. IP address server entries have worked great.

Switching just involves change the System->Server entries and rebooting the cluster. I heard that the reboot isn’t necessarily required but RTMT was broken after the change and I was just more comfortable with the reboot anyway.

From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Jason Aarons (AM)
Sent: 26 May 2015 7:03 PM
To: Gyrion, Larry; Cisco-voip (cisco-voip at puck.nether.net)
Subject: Re: [cisco-voip] Changing DNS entries in Call Manager 9.1.2.10000-28

Everything is hostnames so https works without complaining.  Certificates with ip addresses give warnings.  443/TLS/PKI is the future ☺

You can change CUCM back to ip address but applications and websites, clients like Jabber, will give warnings/errors.  I think your DNS should be rock solid, maybe you need secondary/tertiary dns entries.

From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Gyrion, Larry
Sent: Tuesday, May 26, 2015 5:20 PM
To: Cisco-voip (cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>)
Subject: [cisco-voip] Changing DNS entries in Call Manager 9.1.2.10000-28

We had an issue where we lost outbound calling ability when out primary DNS experiencing an unscheduled outage.
Our DNS entries are by host-name, not IP address.  (it never failed over to the secondary DNS server, other items like computers did and internal and incoming traffic was working fine)

We also use UCCE 9

I’m not sure why it was configured by host name rather than IP address when it was configured a long time ago.

So my questions are:
Is there a valid reason why we use host-names instead of ip addresses?

How can we change from host-name to IP address?
Will this affect the licensing (ELM)? (The below is reference to pre 9.0 CUCM)

From: avholloway at gmail.com<mailto:avholloway at gmail.com> [mailto:avholloway at gmail.com] On Behalf Of Anthony Holloway
Sent: Monday, January 26, 2015 8:13 PM
To: Gyrion, Larry; Cisco-voip (cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>)
Subject: Re: [cisco-voip] Changing DNS entries in Call Manager 8.6.2

The easiest way to view the license MAC, is to SSH to the server, and issue the show status command.

Also, http://cisco.com/go/license<http://cisco.com/go/license> enables you to rehost your own license files without opening a case.  Of course, I don't guarantee you'll be successful, but it's nice to know this option exists.

[Inline image 1]

Another thing to note, you will get 30 days to rehost your license before anything bad happens to your servers, but if you're in a pinch, and you're like on day 28 and you need like 10 more days, you can revert your change, then make the same change again, to restart the 30 day period.

If that was confusing, let me use this example.  If my primary DNS was 1.1.1.1, and I changed it to 2.2.2.2, I would have 30 days to rehost my licenses.  On day 28, I set the primary DNS back to 1.1.1.1, then immediately back to 2.2.2.2, and the 30 days starts over.

Last, buy certainly not least, if you are changing DNS settings, it would be imperative for you to consider what might happen if you changed your DNS suffix.  I cannot speak to your environment exactly, but suffice it to say, certificates are based on names, and names sometimes contain DNS suffixes.  You might start a chain reaction of changes, and as such you should plan that piece out more carefully.  If you're only changing DNS server addresses, then you can ignore this last paragraph.

Good luck.

On Mon Jan 26 2015 at 4:43:19 PM Gyrion, Larry <Larry.Gyrion at deancare.com<mailto:Larry.Gyrion at deancare.com>> wrote:
Looking for some guidance on updating the DNS entries on our CUCM cluster.  A colleague went through the process, but upon entering the command received a warning stating that the change would invalidate our licenses.  Has anybody come across this before, and if so, what was the proper course of action to ensure license preservation?
CUCM 8.6.2

Thank you,
Larry Gyrion | Telecommunications Analyst | Information Technology
Dean Clinic - Corporate offices
1800 W. Beltline Hwy
Madison WI. 53713
Phone 608.294.6201<tel:608.294.6201> | 5406201| Fax 608.280.6852<tel:608.280.6852>
larry.gyrion at deancare.com<mailto:larry.gyrion at deancare.com> | www.deancare.com<http://www.deancare.com/>
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