Redundancy problem for CCM 5.1

Answered Question
Apr 21st, 2009

Hi,

Having problem on the failover of CCM 5.1

I am using hostname for the CallManager for both subcriber and publisher.

I checked the IP Phone Network Configuration,

CallManager 1: hostname of Publisher

CallManager 2: hostname of Subscriber

CallManager 3 TFTP: IP Address of Publisher Active

Assigned the CCM Group which contains the 2 CCM to a device pool which the IP PHone is using.

The IP Phone registers to CallManager 3 (IP address of the Publisher) and when Publisher is down it doesn't register to Subscriber. Also checked the DNS and it is working fine. DNS can resolve the hostname.

Changing the CCM group, publisher as backup and subcriber as primary. Results to phone as:

CallManager 1: hostname of subcriber

CallManager 2: hostname of publisher

CallManager 3 TFTP: IP Address of Publisher Active

Leads to CCM group useless.

However when changing the DHCP(microsft external) tftp setting from:

publisher - primary tftp

subcriber - secondary tftp

to...

publisher - secondary tftp

subcriber - primary tftp

on the phone We get:

CallManager 1: hostname of Publisher

CallManager 2: hostname of Subscriber

CallManager 3 TFTP: IP Address of subcriber Active

So manually changing the primary tftp on dhcp server will force the phone to register on the CCM subscriber.

Phones doesn't seem to register to the backup server when heartbeat is lost. Any ideas?

Thank you!

I have this problem too.
0 votes
Correct Answer by gogasca about 7 years 9 months ago

That means that DNS is not working at all.

Please change hostname to IP address under CCM Admin | System | Server

Remember that when IP Phone is not able to contact cucm it will attempt to register to its TFTP.

So DNS is not working at all.

you can capture packets from ip phone when booting up and that will show u that.

Please verify dns config (ping hostname and fqdn) or change to IP addresses to avoid this type of problems.

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Correct Answer
gogasca Tue, 04/21/2009 - 22:44

That means that DNS is not working at all.

Please change hostname to IP address under CCM Admin | System | Server

Remember that when IP Phone is not able to contact cucm it will attempt to register to its TFTP.

So DNS is not working at all.

you can capture packets from ip phone when booting up and that will show u that.

Please verify dns config (ping hostname and fqdn) or change to IP addresses to avoid this type of problems.

lenapostol Wed, 04/22/2009 - 02:02

Hi,

We thought it was a DNS problem also but we tested it by connecting a laptop configured using the voice vlan of the phones. Did nslookup and those hostnames are resolved without problems so dns resolution works fine.

As for changing the hostname to ip address on the CCM, we are a bit hesitant to do that on an old production environment yet because of problems encountered in the past(e.g. can't access admin page,etc.)

I know it is best practice to use ip address but we are trying to look into other possible solution aside from changing the server to ip add.

gogasca Wed, 04/22/2009 - 02:08

Ok, make sure DNS is configured properly in IP Phones (under network config dns should be correct)and get the capture as in my previous post to see whats happening.

Code of IP Phone if using latest one is pretty stable for this problems so its more likely a configuration problem.

thanks

lenapostol Wed, 04/22/2009 - 02:31

An update. we found out that ip comm works fine. Just not on ip phones.

DNS configured are correct.

Did a factory reset on phone did not help at all :-(

Doing the packet capture and will try upgrading the phone firmware.

Phones are 7940G bdw with 8.0(5.0) firmware.

TIA.

amansoi_5 Wed, 04/22/2009 - 02:46

Hi,

Where exactly u have configured the DHCP server ?

We had also faced similar problem with same CCM version & problems of un-regsitration with Sub. We had configured DHCP pool for IP phones on Cisco Switch wherein phones were not getting regsitered to Subscriber.

The problem was DNS server & domain name not configured in DHCP pool.

We did this & is working fine.Can u cross-check.

regds,

aman

lenapostol Wed, 04/22/2009 - 03:11

Found out the problem after packet sniff.

Looks like the ip phone is trying to resolve the fqdn of the server and the domain given by dhcp is different.

corrected that and works fine now.

Thanks for the help.

@aman,

dhcp server is configured with primary & backup dns server. primary and backup tftp. domain name included.

If ccm is using hostname, if no dns configured then it doesn't know where to go.

Cheers!

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