CUCM provides hostname instead of IP for UDS in a non-DNS installation

[Norbert Mischke]

CUCM 12.5 / 14.0

Jabber 12.5.1 / 14.0.4

Hi,

I try to run a basic CUCM lab setup with Jabber in phone-only mode but without DNS.

I've done the usual tasks to make a non-DNS installation work. 

When I start Jabber I enter the server IP and mode manually, I enter my login URI. I get the correct Username presented, and I have to enter my password. Next step for the Jabber client is to connect to the UDS service.

But here is my problem: The CUCM presents the UDS address as hostname(cucm1) but not as IP address. 

When I add the hostname to the hosts-file of the client pc or add the hostname to my DNS. It works just fine and the CUCM presents all configuration items as IP addresses as I would expect it. But adding the hostname to the DNS is exactly what I try to avoid. 

Does anyone have an idea how I can make the CUCM to send the initial UDS info as IP address?

[collinks2]

try this:

go to system/server, change the hostname to an ip address.

Go Enterprise Parameters configuration,

change the hostname to ip address .

change the cti under uc service to ip address

[Norbert Mischke]

Hi collinks2,

thanks for your reply. I've already changed all hostnames in the configuration to IP addresses and it works as expected, but unfortunately they have no impact to the initial UDS contact address send out by CUCM. 

Cheers Norbert

[b.winter]

Hi,

what exactly do you mean with "initial UDS contact"?

Can you make a screenshot or explain it in more detail?

[Norbert Mischke]

Hi,

let me try. The Jabber login flow in phone-only-mode looks like this ( I know I will miss a few details here):

With DNS:

1: Jabber contacts DNS to resolve DNS-SRV entry "_cisco-uds._tcp.mydomain.local"

2: DNS returns the name and IP of one of the CUCM server.

3: Jabber contacts CUCM 

4: CUCM asks for Authentication

5: Jabber asks user for login credentials and presents them to CUCM, Jabber/user is now authenticated.

6: CUCM sends UDS contact information to Jabber (not 100% sure with DNS, maybe Jabber just re-uses the FQDN from step 2)

7: Jabber contacts UDS server and gets home cluster information via https://UDS-FQDN:8443/cucm-uds/user/USERNAME

8: Jabber contacts home cluster for all other information, logs on and lives happy ever after. 

Installation without DNS but client can resolve the CUCM hostname:

1: User enters login URI and Server IP + contact mode via extended settings

3: Jabber contacts CUCM via server IP

4: CUCM asks for Authentication

5: Jabber asks user for login credentials and presents them to CUCM, Jabber/user is now authenticated.

6: CUCM sends UDS contact information to Jabber 

7: Jabber contacts UDS server and gets home cluster information via https://IP-Address:8443/cucm-uds/user/USERNAME

8: Jabber contacts home cluster for all other information, gets only IP addresses in config files and logs on and lives happy ever after. 

Installation without DNS but client cannot resolve the CUCM hostname:

1: User enters login URI and Server IP + contact mode via extended settings

3: Jabber contacts CUCM via server IP

4: CUCM asks for Authentication

5: Jabber asks user for login credentials and presents them to CUCM, Jabber/user is now authenticated.

6: CUCM sends UDS contact information to Jabber (This is the Problem, because CUCM send a hostname, not a IP address)

Error: Cannot communicate with Server

A screenshot of the UDS section of the Jabber Diagnostics Window is attached to the initial post.

Cheers Norbert

[b.winter]

Have you also applied and resetet the CUCM nodes under "System" --> "Cisco Unified CM"? (Probably shouldn't be done in a productive system, since every device is being resetet)

Because it will not automatically update all the device config files, if you just change the "server" from FQDN to IP

By checking the URL "https://<CUCM>:8443/cucm-uds/user/<username>" you will see a difference in the output of the XML.

[Norbert Mischke]

It's a lab environment. I've done a full cluster reboot. 

The Problem is not with the configuration files. The issue is that the CUCM sends a hostname as initial UDS contact, that's a few steps before the config files get pulled by the Jabber client. (The config files itself are fine, all with IP addresses)

Cheers Norbert

[Jonathan Schulenberg]

I’m struggling to find a supporting document at the moment but DNS is required for Jabber (and the Webex app); you cannot fully disable it. The BU made this change in the 8.x-9.x timeframe and, frustratingly, Cisco has been taking documentation for EoL versions down. I’ll spend a few more minutes looking just in case.