WRNING: DNS is unreachable by CUCM.

[Ana68]

Hi everyone,

I've installed a CUCM version 10.5. I've got the warning, that the DNS is unreachable. 

By running the command: utils diagnose test, I can see that all terms are actually passed.

I've restarted the Tomcat services as well. 

Im working with vmware workstation 12.

Do I have set something by virtual Network Editor?

I will be thankful for any good suggestion.

 I think because of this warning I can not open the GUI interface of my CUCM. is that right?

Thank you in advance.

Ana

[Vineet Kumar Gautam]

Hello Ana,

can you please paste the output of " utils diagnose test "?

Vineet.

[jason-mcgee]

Ana,

There are so many different possible routes to go with this one:

Ping your DNS server from the CLI for CUCM and see if you can reach it that way. I assume you added the record to your DNS server for CUCM. Have you tried to reach the GUI via IP address instead of name resolution?

Do you have a backup DNS server? Have you used that as well and if not, can you add it and see if it is reachable?

Run a utils service list from the CLI of CUCM and see if all relevant services are started.

Start with that and we can go from there. Good luck.

Jason

[Ana68]

Hi Jason, 

you were right, I set the wrong IP address for my DNS. I just set it now in the right form. But the pinging is absolutley not possbile from my machine, not from my Windows server as well. 

It will be great, if you have any solution for this problem. 

Best regards

[Jaime Roldan]

Hello Ana,

DNS unreachable does not necessarily mean that you have no connectivity to the DNS server.

Let's do the following:

[+] Go to the CLI of your publisher and issue "show network cluster"

[+] This will give you a list for all the nodes in your cluster. For this time let's say that we have only 2 nodes in the cluster, cucmpub.test.com (10.0.0.1) and cucmsub.test.com (10.0.0.2)

[+] Now let's make sure that that the external resolutions work. to do so you can test the following:

"utils network host cucmpub.test.com" or if there is no domain you can do "utils network host cucmpub"

This commands will give two resolutions, the internal resolution and the external resolution.

[+] Now if the DNS is reachable and able to process the request, you will see that cucmpub.test.com should be able to to resolve into 10.0.0.1 externally

[+] Now let's do the same for the subscriber and make sure that the DNS is able to resolve the subscriber as well into the correct IP.

[+] now that we have done the forward resolution we need to check the reverse resolution. to do so just do "utils network host 10.0.0.1" and the external resolution should show you the original hostname or FQDN of the server "cucmpub.test.com"

CUCM will say that DNS is unrachable if:

1) External resolutions cannot be completed

2) External resolutions do not match with internal resolutions

3) If reverse resolutions are not configured. Both forward and reverse resolutions should match with the internal resolutions.

Regards, Jaime.

Please upvote if helpful !

[jason-mcgee · Accepted solution]

Ana,

Well we have our work cut out for us. I will try and help you as much as possible, but without actually seeing your network, this could be challenging.

The utils service list is actually 3-4 pages long, you would need to do a shift/page up or shift/page down to see all of them.

1) Did you record all of the information that CUCM asks for during install? User Name, Passwords, IP Address, DNS server, Name of server as part of the FQDN?

2) From your desktop or laptop have you tried to ping the IP address that you assigned to CUCM. Have you tried NS Lookup to make sure the record is recorded correctly?

3) From the CLI enter show myself >>> verify the name of the server

4) From the CLI enter show network eth0 >>> verify IP address >>> Ping that IP address from your laptop or desktop. 

Hopefully you will be able to find the server at the end of these steps and catch any possible errors in set up and we can go from there. Good Luck.

Jason