Intermittent VLAN Issues

[cchsbrad]

I recently moved our IP phones (mostly Fanvil devices - approximately 40) from our default VLAN to a separate VLAN. Since then I've been having a lot of intermittent issues with individual phones not working correctly or losing connection with the server. A simple phone reboot fixes the issue for a few days and then it will randomly have issues again. The 3CX server is still on the default VLAN. I did not make any changes to the device settings or server settings. Was I supposed to? I'm somewhat of a newbie with VLANs.

Note: The majority of phones are working flawlessly. I'd say around 15 are experiencing these issues.

I'm at a loss and would appreciate any help you may have. Thanks!

 

[JohnS_3CX]

Hi Brad,

VLANs are not something we can help with, this comes down to the networking hardware doing what it needs to do, so that the packets reach their destination.

But in your case, does the phone do the tagging or the switch port?

 

[cchsbrad]

The switch port. Should I also be configuring the phones for the VLAN? I don't understand why the issues seem so random and only for some devices.

 

[JohnS_3CX]

I'm afraid I cannot be of assistance on that matter, you might have to run wireshark captures and see whether the phones truly stop registering or whether they are trying but your network ports are no longer passing the traffic on to the PBX.

Port tagging is indeed better than having the phones do it. They should not be aware of VLANs if possible.

 

[cchsbrad]

Thanks for the suggestions. I'll see what I can figure out.

 

[JohnS_3CX]

Another little quick "trick" is to hook up a laptop or PC to the phone's secondary LAN port.

If it actually lost the network connection, the PC will probably not work either (although not a foolproof test).

You best bet will be the captures, those will definitely tell you whether the phone still tries to reach the PBX, whether the PBX actually received the SIP messages and replied, but also whether the replies got back to the phone.

 

[cchsbrad]

One last thing: Is it preferable to have the 3CX server on the same VLAN as the phones? Does it matter?

 

[SweetAction]

One last thing: Is it preferable to have the 3CX server on the same VLAN as the phones? Does it matter?

We usually do, although we have many more systems that have 1 3CX system providing multiple sites and/or VLANs with service, so it's not required.

 

[JohnS_3CX]

It's preferable so the phones and PBX can see each other directly (reduces issues related to VLAN routing).

It also helps with multicast traffic, as we often see people having issues where multicast does not traverse across 2 VLANs