and Zero Config and GDMS intergration handing our wrong IP



I’m starting to notice that since and in if we have the Network mode set to route.

Zero config will sometime set the Server IP for the handset as the WAN IP or the SDP address. even when its in the same subnet range as the LAN.

This is starting to cause issue for our customers with multiple sites connected via VPN.

even smaller customer with a single site some phone are getting the LAN IP (Correctly) others are getting the WAN IP (incorrect)

Also in if we are connecting GRP phones the auto setup in GDMS only supplies the WAN ip so even if the phone are on the LAN side we can auto provision, and it means we then have to update all changes manually.



Why route mode?

Curious as you apparently have VPNs, which implies that the UCM is sitting behind router/firewalls as the UCM is not a VPN server capable device?

I am also a little confused as to why the use of both GDMS and ZC.

I am not disputing what you report, but rather questioning route mode usage rather than switch or dual mode (if really needed).


the reason we use route is because the Carrier uses IP Authentication on a dedicated Voice Modem for VOIP trunks, so we use the WAN interface in route mode with DHCP from the Carrier so only the UCM is on the Voice Services. Very common in Australia to do this due to low bandwidths. generally we install 2 VDSL (AUSTRALIAS CRAPPY NBN) service. One for Data one for VOICE

if we did it all on one network we’d have to add additional Static Routes in the Data router to get the VOice to route to the other gateway this will increase the overheads on the Data network and mean we have to program an additional route and generally customer don’t like us doing that. not to mention an additional point of failure and we would have to do double NATTING. so it easier just to use a vdsl modem direct on the WAN and the UCM get a PUBLIC IP which is blocked by the Carrier from outside traffic thus making the UCM appear directly on the Carrier Network.

We have to use GDMS and ZC as i cannot get ZC to push to GXP phones.



Got it. Sorry, not able to help much, as I have too many questions in trying to understand the full topology that it would probably seem rather odd to you and not helpful. I now understand the route issue and why, still other questions pop-up.

The only thing I can suggest is to Wireshark it and see if you can capture a phone making a DHCP request and finding out who issues the WAN IP. It would seem strange indeed that a F/W change would make that drastic of a change, but then again…who knows?


Thanks for you assistance Grandstream got back to me and told me that it is an issue that they are trying to resolve.



Thanks for letting us know.


Woot! I have spent far too much time with my UCM6510 and two UCM6208 trying to figure out what I was doing wrong.

Discovering your post is a beautiful thing.

All three are running and did exhibit the issue with All are using “Route” Method in Basic Settings under Network Settings under System Settings.

I’ve been manually fixing phones, all GXP2135 and GXP2170s, with a smattering of WP820s and DP750s, when they were reported to me. Logging in and checking 250 phones wasn’t in the cards.

Even using P codes in Global or Model Templates were being overwritten with the incorrect SIP Server IP address upon Zero Config.


hey eric have you had any issue with p codes in Global config? with



I do not currently use any Global Templates.

I did try using Global Templates and Model Templates to force the SIP Server P code while troubleshooting. I found that using the SIP Server account P code for an account that I had configured in Zero Config was always overwritten with the incorrect SIP Server.

I found when I started using this equipment in 2016 with older UCM firmware that the stacking of Global Templates and Model Templates was flaky, so I have always been in the habit of putting everything in the Model Templates I deploy.


If speaking of pcode usage in an UCM in conjunction with zero-config, then as far as I know the only place you can use pcodes is in the model templates. The others support basic functionality, but not pcodes and the settings are applied in a hierarchic mode where the model template will take precedence.


You an also add pcode on exact phone settings.