IP Phone registration - Hanging @ config IP

f.sorrentino · ‎08-08-2011

Hi all,

I am trying to configure a couple new IP phones but they will not register with the call manager. I have added numerous devices before and the configuration is good. There are plenty addresses available in the DHCP pool. When the phone boots up they hang on "Configuring IP". I did only have about 2 licenses left so I have deleted some old hardware and now have 40 available. It is on the right VLAN. I cannot see anything coming up on syslog to suggest what the issue is.

Any ideas?

Thanks.

Joseph Martini · ‎08-08-2011

Can you take a packet capture from the phone so we can take a look at what is happening at the network level? Here's a guide for how to do that: https://supportforums.cisco.com/docs/DOC-11735

f.sorrentino · ‎08-09-2011

Thanks joemar2,

I am not int he office today but will get it done and provide the results.

Thanks again

f.sorrentino · ‎08-10-2011

Hi,

Ok I have attached a couple of.pcap files which has the captures from my PC of all traffic coming to.from the phone. Hopefully it will shed some light onto this..

Cheers

Joseph Martini · ‎08-10-2011

Thanks for the captures, if you filter on "bootp" you'll see the phone requesting to use 172.16.12.37 and it eventually gets an ACK back from the DHCP server, however in the ACK there is no option 150 or option 66 telling the phone what TFTP server to use. Also we can see in the CDP packets the phone is using VLAN 100 for it's voice VLAN, make sure that's the correct VLAN.

Joseph Martini · ‎08-10-2011

One other tip, in the network configuration settings you can try and toggle the "IP Address Released" option, which will make the phone forget it's last IP address so that the DHCP process will start with a Discover from the phone instead of a Request for it's last used IP address. Just remember once you set the IP Address Released option to YES you have to go back into the network settings and set it back to NO or else the phone will not get an IP address.

f.sorrentino · ‎08-10-2011

Hi Joemar2,

Thanks for the info.

I have had a look at what you said and the phone(s) are defniately in the correct voice vlan of 100 as config has been checked and also disconnected a working phone to test. Just checked the DHCP pool and the option 150 is there.

ip dhcp pool Voice

network 172.xx.xx.0 255.255.255.0

default-router 172.xx.xx.254

option 150 ip 10.xx.xx.1

why are exising phones able to be disconnected and reconnected with no issues. Do they keep a record of the last tftp server? If not then how are they getting to the TFTP server? The new phones aren't getting the option 150 so cant see any reason that would be different for existing ones.

I tried toggling the "IP Released" option but just goes back to "Configuring IP".

Thanks

raychoiusyd · ‎08-10-2011

Hi Franco,

I've had the exact same problem before. What I did was disable DHCP in the Network Config on the phone, saved it and re-enable and it and saved. This seemed to clear the problem.

Cheers

f.sorrentino · ‎08-11-2011

RayChoi,

I can give it a go but I am unsure if it will make a difference as it appears that the IP phone is getting a response with no option 150. Once joemar2 mentioned this i looked into the ACK that was sent from the DHCP server and it was coming from the wrong server - it was coming from a windows server which is not the DHCP server for the voice network. I need to have a look why the voice DHCP pool is not handing out IP's. No changes have taken place on the network and there are over 100 addresses remaining in the pool.

I turned on dhcp debugging with ter mon and reconnected a phone...cannot see any output for the dhcp negotiation.

AudiAthree,

The phone does not get an IP address.

Thanks.

Franco

AudiAthree_2 · ‎08-10-2011

just to a phone reset, and see if the phone gets an ip address, and under settings-network configuration-IPV4- check if it gets the correct IP and check if it can see the TFTP server

f.sorrentino · ‎08-16-2011

So found the issue. Whilst joemar2 was correct in that one of the DHCP servers wasnt handing out option 150 this was because it was a windows based server which is not used for the voice network. After looking at the DHCP process i found that there were numerous conflicts which for some reason were stuck despite there being no conflict. I cleared these conflicts and phones now registering. Why this issue caused the DHCP server not to respond I am unsure.

When I was capturing the packets I could not see any packets coming from the DHCP server, once the conflict cleared I saw the full dhcp process. Even strange issues have the most obvious of answers!

Thanks.

Joseph Martini · ‎08-20-2011

"I found that there were numerous conflicts which for some reason were stuck despite there being no conflict"

Which conflicts exactly, I see that you found one DHCP server that did not provide an option 150 address, what other conflicts did you find?

f.sorrentino · ‎08-21-2011

Hi joemar2,

I should have been a little clearer. By conflicts I meant DHCP conflicts which meant that these addresses were unavailable for lease - these conflicts had been there for months. For some reason this caused issues with the actual DHCP server itself as the only dhcp packets were those coming from the client. No packets were coming from the server despite it receiving the broadcast requests. Once the dhcp conflicts were cleared (clear ip dhcp conflicts *) I ran another capture and the full dhcp process could be seen.

Thanks.

Franco

Joseph Martini · ‎08-22-2011

Got it, thanks.