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New Member

TFTP ip config changes!!

I have a Vlan network at customer site and my CO, where the CCM is. used ip helper-address command on customer router to get a dhcp config from my Dhcp server at the CO. It captured the IP(Shows in current lease table and in phone itself) But the TFTP ip address in phone settings ends up being either another router interface on customer end or DNS server at CO. PS, no registration!

Stranger thing is phones that worked fine before this config don't now, the 7905 works fine in this network, config.

2 7960 register with DNS address as TFTP address and work fine, and one 7960 refuses to register with the DNS address in place of the TFTP server address.

Any idea's?


Re: TFTP ip config changes!!

Make sure TFTP address in IP phones are not manually assigned. Check to see if DHCP scope options are correct.

Here is a good document to troubleshoot DHCP and TFTP problems

Hope this helps.

New Member

Re: TFTP ip config changes!!

Thanks for that, but where is the 'Cisco Network Registrar' located? (Solution item #4)


Re: TFTP ip config changes!!

Cisco Network Registrar is the name for cisco DHCP server. If you are using any other kind of DHCP server (Microsoft for ex.) you can skip step #4.

New Member

Re: TFTP ip config changes!!

make sure you are IP phones are not getting IP Address from the Data Subnet.

Super Bronze

Re: TFTP ip config changes!!

What DHCP server are you using?

Is the DHCP server correctly handing out addresses to other Voice subnets? If not it could be a config issue on the DHCP server - Option 150 for tftp is non-standard on Windows systems for example, so you need to ensure it's added as an IP Address (or array of IPs) or you'll get problems.

If it is correctly serving other subnets then compare your configs there, or try sniffing for the responses being sent from the server...


Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: TFTP ip config changes!!

is you DHCP option 150 set correct for that subnet? Also the phones that are working are probably working off their last known good config, even though DHCP is wrong. If you where to take all the phones to a segment that worked and allowed them to boot up and register, they would all end up working on the subnet that is not currently handing out the correct tftp info.

New Member

Re: TFTP ip config changes!!

Sorry for the lapse in time...

The DHCP server is now giving the addresses, but only cause I have a DHCP local to the phones handing it out. When I was trying to have my MS DHCP server with the 150 option, sending the info remotely, then I was having the problem. I believe it was a routing issue. I am having a similar issue in another part of my network where I am getting one direction voice! Need to do some cleanup, but thanks for the posts.