Server 2012R2 DHCP reservations problem with my VOIP equipment?



  • I setup a test FreePBX instance on Vultr the other day and I was having problems getting my phones to register so I started troubleshooting and found that all of my phones are getting the wrong gateway address from DHCP. All of the phones have reservations in Server 2012R2 DHCP server. So I deleted the reservation for one of the phones and made a new reservation with the same address, rebooted the phone, and it took all the proper settings this time around. This seems to only affect my phones (Yealink phones, a couple Cisco SPA112's, snom PA1) that I've noticed, none of my other reservations (linux servers, printers, etc.) are taking the wrong gateway address...

    Is it expected behavior for old reservations to keep the settings of when they were first made, or is something funky going on with my DHCP server? Is this just coincidence and actually a problem with the phones?

    Is there something I can do to get my phones to take the correct gateway address without recreating all of the reservations?

    Am I missing something else entirely? Who knows 🤷♂



  • It is not normal for them to get a different gateway unless the DHCP Server is configured improperly. What do you have for the dhcp reservations?



  • @dbeato said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    What do you have for the dhcp reservations?

    What do you mean? Just the normal reservation setup on Windows Server. Hostname, IP address, MAC, and Supported Types: "both". I can't find any presence of my old router which the VOIP stuff seems to be clinging onto.

    003 Router in scope options points to the correct gateway address, too.



  • @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    h the same address, rebooted the phone, and it took all the proper settings this time around. This seems to only affect my phon

    When was the gateway changed compared to when the phone's reservations were made?



  • Assuming the reservations were made before the gateway was changed, and the phones were online before the change - i.e. they were working with the old gateway - perhaps the phones aren't respecting the updated information from DHCP.

    Did you power off a phone wait 1 min, then power it back on and see if got the updated default gateway when using an old reservation?



  • @Dashrender Yeah, the gateway was different back when the reservations were made a couple years ago. I just tried another phone by deleting the reservation and recreating it, then rebooting and it gets the proper address.

    The other gateway has been gone for at least 6 months. The phones have been for sure powered off multiple times for a few minutes. Whenever I update my poe switch firmware they power off for the duration of the reboot, sometimes up to 5 minutes I would guess. I just unplugged one phone for 10+ min and it still has the wrong address. I even reset another phone to factory settings and it still took the wrong address. That's why I think it's something with the DHCP server.



  • @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    @Dashrender Yeah, the gateway was different back when the reservations were made a couple years ago. I just tried another phone by deleting the reservation and recreating it, then rebooting and it gets the proper address.

    The other gateway has been gone for at least 6 months. The phones have been for sure powered off multiple times for a few minutes. Whenever I update my poe switch firmware they power off for the duration of the reboot, sometimes up to 5 minutes I would guess. I just unplugged one phone for 10+ min and it still has the wrong address. I even reset another phone to factory settings and it still took the wrong address. That's why I think it's something with the DHCP server.

    OK - yeah weird... so DHCP is providing bad info... you could wireshark that shit to prove it.



  • Do you guys even use reservations for phones? I rarely even touch them, so I guess it wouldn't be that big of a pain in the ass to just let them get a random address from the pool.



  • @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    Do you guys even use reservations for phones? I rarely even touch them, so I guess it wouldn't be that big of a pain in the ass to just let them get a random address from the pool.

    I do not. I don't know why you would need to.



  • I don't ever reserve IP for phones.



  • @wrx7m said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    Do you guys even use reservations for phones? I rarely even touch them, so I guess it wouldn't be that big of a pain in the ass to just let them get a random address from the pool.

    I do not. I don't know why you would need to.

    idk I guess I just thought it would be easier to manage them. When we first got the phones I set them all up manually from the web interface and there was a lot of experimenting going on, I always knew extension 103 would be x.x.x.103, etc. if somebody had an issue, I knew their extension and automatically knew the IP of the phone.



  • @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    @wrx7m said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    Do you guys even use reservations for phones? I rarely even touch them, so I guess it wouldn't be that big of a pain in the ass to just let them get a random address from the pool.

    I do not. I don't know why you would need to.

    idk I guess I just thought it would be easier to manage them. When we first got the phones I set them all up manually from the web interface and there was a lot of experimenting going on, I always knew extension 103 would be x.x.x.103, etc. if somebody had an issue, I knew their extension and automatically knew the IP of the phone.

    I haven't dealt with anything other than shoretel for 9 years, now. I don't need to know the ip of any phone. The MAC is what is the most important. Everything is cross referenced so you can find pretty much everything if you only know one attribute. That's why I wouldn't care about the IP. Obviously, I haven't used freepbx, so I don't know how useful it is to know the IP there.



  • I never use reservations for phones.

    Specifically with Yealink phones, I set the DHCP hostname value in the config file.

    So when I am on the network, I can easily just ping ext103.domain.local and shit..

    Or If I look at the DHCP server lease list, I see the hostnames listed as ext101, ext103, etc.

    c1f3dca6-fa20-4b66-9d59-87af092bf42f-image.png



  • @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    @wrx7m said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    @bnrstnr said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    Do you guys even use reservations for phones? I rarely even touch them, so I guess it wouldn't be that big of a pain in the ass to just let them get a random address from the pool.

    I do not. I don't know why you would need to.

    idk I guess I just thought it would be easier to manage them. When we first got the phones I set them all up manually from the web interface and there was a lot of experimenting going on, I always knew extension 103 would be x.x.x.103, etc. if somebody had an issue, I knew their extension and automatically knew the IP of the phone.

    I also do not manually manage phones like that.

    You were learning, so that is pretty common. But take the time now and move to centralized provisioning.

    I guess I should write up some up to date posts on the subject.



  • @JaredBusch said in Server 2012R2 DHCP reservations problem with my VOIP equipment?:

    I never use reservations for phones.

    Specifically with Yealink phones, I set the DHCP hostname value in the config file.

    So when I am on the network, I can easily just ping ext103.domain.local and shit..

    Or If I look at the DHCP server lease list, I see the hostnames listed as ext101, ext103, etc.

    c1f3dca6-fa20-4b66-9d59-87af092bf42f-image.png

    Love this idea