CUCM hostnames vs. IP addresses

[Tieken Maas]

Hi, everybody!

Just want to clarify some unclear points.

I've set up a cluster of two CUCMs 7.1 in my lab. During the installation process I had to provide hostnames for both servers, so I chose cucmpub an cucmsub. I decided to refrain from using DNS services, so I skipped this step. Now, when I go to System -> Server, I see a list of two servers defined by hostnames I mentioned above.

As I decided not to use DNS services, my phones connecting to the TFTP server get a list of two CM servers defined by hostnames, so they cannot resolve these names and therefore default to the TFTP server which is the publisher. So, when I look through the network settings of the phones, I see that CM 1 = cucmpub, CM 2 = cucmsub, CM 3 = 192.168.1.1 (Active). This is not ok, of course.

I guess there can be two options:

a) configuring a DNS server and providing both CUCM servers with relevant info about the DNS server. DHCP pool that provides phones with IP addresses should also include info about the DNS server. Will it work?

b) i need to do something about hostnames of the CUCMs so that servers would be defined by IP addresses rather than hostnames. So System -> Server would show servers as defined by IP addresses. I've got no idea how to do it, because the link frequently refererred to seems actually to deal with different things:

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/install/7_1_2/ipchange/ipchg712.html#wp41802

The section "Changing the Host Name for Servers in a Cluster" that seems to be the most relevant includes the steps (for subscriber) that puzzle me a bit:

1. Navigate to Settings -> IP -> Ethernet.

2. Change IP address and, if necessary, the default gateway to the new address.

Why should I change IP address if the only thing I need to change is just a hostname???

I'd be very grateful for any ideas.

Regards,

T.

[Aaron Harrison]

Hi Tieken

Re: your two points:

a) You don't need CUCM to know about DNS for this. The phones are getting the list of servers by name, so the phones need to resolve them. You would assign DNS servers to the phones via DHCP, and ensure that you have added the hostnames to that DNS server in whatever domain the phones search by default (also set via a DHCP option).

b) In the system/servers menu, you can just change the names to IPs and this will then be written to the TFTP files. This is a very common step in CUCM deployment stemming from the 'stay away from external depencies' school of though, which is kind of dying now that various apps related to callmanager are getting more tightly integrated to customer environments. The 'settings/ip/ethernet' menu would change the IP of the server - you don't want to do this, you just want to change the references sent to the phones though TFTP.

Regards

Aaron

[Tieken Maas]

Thank you, Aaron! I'll check it and let you know if this has worked.