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Solved New phones on LAN not showing on Phones page

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jbland

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3CX v18.0 Update 2 (3cx appliance ISO)
Fanvil X5U (on latest 2.4.12 firmware from 3CX, with factory reset)

Newly connected phones are not showing up on the Phones page in my admin panel. It's been a while since we added a phone, so I'm not exactly sure when this started but it had to have been within the last 6 months or so since we added one back in July. There have been many system updates since then, including the jump from 16 to 18.

The phone and PBX are on the same subnet, and I can ping from the phone to the server and vice versa. I can packet capture and see the multicast packets coming from the phone at boot.

We have two other model phones to test with; a Snom D717 and Fanvil X5S. Both exhibit the same symptoms, none show up on the Phones page of the admin panel. To me, this points at an issue on the server level rather than something wrong with the phones.

It seems like my 3CX server is not 'listening' for these multicast events, but I have no idea how that could be the case. Everything is on DHCP so subnets are correct, and we have never used Option 66.

Any ideas on what to try next?
 
I have followed the guide at https://www.3cx.com/docs/plug-and-play-ip-phone/

The phone web UI confirms SIP PnP is enabled and the server address is 224.0.1.75:5060 as expected.
Switches are Meraki MS-225 and they have worked in the past with PnP, should have no problem supporting it.
3CX terminal shows 'sip.mcast.net' on the correct adapter when running 'netstat -g'
 
Within the dhcp server do you have any option configured I.e. option 66. If so remove it
 
No we do not. Only options set are 003 (router), 006 (DNS Servers), and 015 (DNS Domain Name)
 
Hm, for what it's worth: Option 66 works to allow provisioning. Set up the phone in admin panel, plug it in and it works.

I'd still rather get PnP back to working, as it's a much easier option for my technicians. At least it's nice to have a work-around.
 
What network hardware are you using?
 
Cisco Meraki
 
Thanks! I had that thought and disabled IGMP Snooping yesterday afternoon. After rebooting some phones this morning, they are still not showing in the admin panel. I wonder if the switch might need to be rebooted after that change...
 
Hi,
3CX v18.0 only works with IP addresses that fall into private classes (A, B, C). I'm not sure if your server's IP address is a valid address.

The Internet Engineering Task Force (IETF) has directed the Internet Assigned Numbers Authority (IANA) to reserve the following IPv4 address ranges for private networks:[1]: 4 

RFC 1918 nameIP address rangeNumber of addressesLargest CIDR block (subnet mask)Host ID sizeMask bitsClassful description[Note 1]
24-bit block10.0.0.0 – 10.255.255.2551677721610.0.0.0/8 (255.0.0.0)24 bits8 bitssingle class A network
20-bit block172.16.0.0 – 172.31.255.2551048576172.16.0.0/12 (255.240.0.0)20 bits12 bits16 contiguous class B networks
16-bit block192.168.0.0 – 192.168.255.25565536192.168.0.0/16 (255.255.0.0)16 bits16 bits256 contiguous class C networks
 
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It may also be worth restarting the 3CX SIP Server at some point.
It has happened to me once or twice and I think it has been right after OS updates sometimes.
 
Our VoIP VLAN is within the private class A subnet. We've restarted the server multiple times, unfortunately that hasn't worked to fix it.
 
jbland said:
Our VoIP VLAN is within the private class A subnet. We've restarted the server multiple times, unfortunately that hasn't worked to fix it.
Click to expand...
In that case, in order to rule out certain things, what I would do is this:
  1. Log into the 3CX Management Console
  2. Go to Dashboard --> Activity Log, here select the correct NIC (NOT "All Interfaces" if you have that option...) in the drop-down and press "Capture".
  3. Factory reset one of the IP Phones that is not appearing and wait until it boots up again in a Factory Reset state.
  4. In the Management Console now press "Stop" and press the "here" button to download the packet capture.
  5. Open it with Wireshark, use a filter like ip.src_host==<IP of the IP Phone> then search for an entry that has a Destination IP of 224.0.1.75 and Destination Port of 5060
If you don't see anything like this, it means that the Multicast packet is not even reaching the server, so you need to check the network nodes why it isn't.
If it does, it may be something on the OS or even 3CX, like e.g. the specific IP being in the 3CX IP Blacklist.
 
Thank you Nick, I've confirmed the multicast packets aren't reaching the server. Seems to be a networking problem; I'll keep digging down that road.
 
Found my problem, and it is indeed specific to Meraki. There's an option in switch settings to 'Flood unknown multicast traffic'. We had this set to disabled last semester while tracking down a broadcast storm. While disabled, multicast packets are discarded.

Enabling that option made the new phones show up in the list properly, PnP provisioning working as expected.

Thanks everyone for your help!
 
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Very glad to hear you found the source of the problem!

I will set this thread as 'Solved'.
 
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