SNOM715 VLAN issue

[SvenSip]

Hi,

I have an issue with the SNOM715 at the moment. The phones are working fine as long as they are getting an IP inside the LAN subnet but as soon as I change the switchport to our voiceVLAN they are having troubles maintaining registration.

I'm not sure in what direction I have to look for the solution. (3CX config, phone config, firewall config, ...).

Things I have done already while scouting for a solution:
- enable keep alives (60).
- factory reset phone and then reconnect it.
- update to latest firmware.
- uncheck/check "Disallow use of extension outside the LAN (Remote extensions using Direct SIP or STUN will be blocked)" in User options of the extention the phone is linked to.
- confirm internet connectivity by plugging in laptop in the switchport where the phone was plugged in.
- reboot switch.

Some extra info that might be useful:
- when looking in the 3CX management console where you have the list of all phones, the phones in the voiceVLAN are showing their IP as if they have our current LAN default gateway IP although when the phone boots its showing an IP inside vlan on the phone lcd.
- eventhough the phones have trouble maintaining registration (it toggles between registered and not registered) I can make and receive phone calls both internal and external.
- we are using unifi switches so there shouldn't be a trunking problem.
- eventhough the phone is 'working' it doesnt have any button lights (green/red) active as opposed to when its connected inside our LAN.

Any help is appreciated. I will keep looking into this myself this afternoon and edit if I happen to come across a solution.
You can always contact me at [email protected] as well.

 

[JohnS_3CX]

Hi Sven,

enable keep alives (60)

normally you should not need to modify anything at all in the phone to make this work

uncheck/check "Disallow use of extension outside the LAN (Remote extensions using Direct SIP or STUN will be blocked)" in User options of the extention the phone is linked to

this is only for STUN, it does not apply in LAN deployments

when looking in the 3CX management console where you have the list of all phones, the phones in the voiceVLAN are showing their IP as if they have our current LAN default gateway IP although when the phone boots its showing an IP inside vlan on the phone lcd.

That doesn't seem right, something on your network is giving that information to 3CX.

we are using unifi switches so there shouldn't be a trunking problem

don't be quick to dismiss this just yet, based on your description the networking is suspect

eventhough the phone is 'working' it doesnt have any button lights (green/red) active as opposed to when its connected inside our LAN.

If you are referring to BLFs, this would imply the SIP SUBSCRIBE events are failing


So given that all this happens while specifically on the VLAN, it would be reasonable to suspect that the network is part of the problem. Wireshark is your best friend for this kind of thing, but it also requires a more in-depth knowledge of SIP.

A good starting point to troubleshoot this is to start a pcap on the phone as soon as it starts up, and stop as soon as it loses registration.

At the same time, you can run a pcap on 3CX which you will also stop as soon as the phone loses registration.

Those two files should show something along these lines when you compare them in Wireshark:

- The phone seen sending a request (ie. classicstun or REGISTER) to 3CX (seen in phone capture)
- The 3CX machine seeing the request and replying (seen in PBX capture)
- The phone seeing the reply coming from 3CX (seen in phone capture)

If those two captures do not agree (ie. one side sends something and the other side doesn't ever receive it) the expected result is loss of registration.

If this test confirms what we suspected, you will have to figure out what in your VLAN configs needs corrections to allow full traffic. Unfortunately we cannot help you on how to setup your networking hardware, you will have to figure this part out yourself.

If you think this is not something you can undertake, it might be a good idea to contact a 3CX Partner and get them to help you with your deployment. Alternatively you might also get help from a network specialist.

At the end of the day, the phones require unimpeded traffic and the current VLAN conditions appear like they are not providing this. And as a final note, ensure both the PBX and the phone networks are providing RFC1918 compliant IP addresses - this is mandatory.

 

[SvenSip]

Thank you very much for the detailed reply. I'll have a look into everything you mentioned.