cisco phone not getting ip address

[susim]

Hi all , 

Cisco 2950 switch 

Phone and dhcp server are in the same default vlan .PC's are getting ip address from dhcp server but not the phone 

Thanks

[Aaron Harrison]

Have you added an IP helper-address on the router interface in the voice VLAN pointing at the DHCP server?

Have you configured anything to route between the VLANs?

Aaron

[susim]

Hi Aaron 

Phone and dhcp server are in the same vlan , Still do i need ip helper address ? .

Actually i did not do any routing .

Thanks

[Richard Burts]

If the phone and the DHCP server are in the same vlan then you do not need ip helper address.

You have not given us much detail and there are multiple things that might cause this problem.

Is the phone expecting to be in a vlan that is different from the PC?

Are there enough IP addresses in the scope for both PCs and phones?

Are there log messages on the server that might help identify the problem? Is the server recognizing that it is receiving requests from the phone?

HTH

Rick

[susim]

Hi Rick 

I was doing a test with single 2950 switch  , the vlan is the default (vlan 1 ) .dhcp server and  the phone are in the same vlan

Are there enough IP addresses in the scope for both PCs and phones?

There is no log related with this problem in the dhcp server 

Thanks

Yes. 

[Aaron Harrison]

OK, so if you have one VLAN, you should have one scope.

You should be expecting the phone to get an IP in the same subnet as your PC, and the same subnet that your DHCP server has an addres in.

Assuming your DHCP server has spare IPs available, the only ways this could mess up are:

- You have an incorrect 'admin vlan' set on the IP phone so it's trying to use a VLAN that doesn't exist

- You have set a VVLAN on the switch port that is confusing it

- The phone may be otherwise configured for static IP or similar.

- The phone may be broke. Sometimes you see them power up but the network card isn't working (usually with a 'network disconnected' message on the screen). Not massively likely.

Aaron

[susim]

Hi 

I can see the  mac address has registered  on the switch . And i have tried couple of phones ,  result was same  . 

Then i did run a packet sniffing using wireshark . 

I could see  dhcp discover from the phone   and offer from the server  a couple of times . 

i am attaching the dhcp offer part  from the  wireshark . 

And i saw one error  also 

Error part 

    Option: (150) TFTP Server Address
        Length: 11
        TFTP Server Address: 49.48.46.48 (49.48.46.48)
        TFTP Server Address: 46.55.49.46 (46.55.49.46)
        [Expert Info (Error/Protocol): Option length isn't a multiple of 4]
            [Option length isn't a multiple of 4]
            [Severity level: Error]
            [Group: Protocol]
    Option: (255) End
        Option End: 255

i don't have any idea about the Tftp server address mentioned   above . 

[Aaron Harrison]

It looks like you have a misconfigured DHCP server. You'll have to check the Option 150 config on it.

Is it Windows/IOS or other?

Aaron

[susim]

Hi

I deleted option 150 ,it is working now  . As far as i know cisco phone required option 150 for tftp ?.

Thanks

[Aaron Harrison · Accepted solution]

Hi

Generally you are advised to use Option 150, however there are other ways that the phone can find the server:

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/7_1_2/ccmsys/accm-712-cm/a02tftp.html#wp1023004

Aaron