Duplicate Phone Entries

[InHarmsWay]

I am having an issue with v20 where two phone entires show up for most of the users with the same phone and mac address. The IP's are different, the second entry shows the IP of the internet gateway. Its an on-prem phone system. What causes this?

 

[JohnS_3CX]

Hi,

This is pretty clear, the PBX sees the phone registering from two different source IPs and you need to figure out why.

Hint: You also see the IP of the gateway, so that tells you there's possibly a NAT between the PBX and the phones, generally a very bad idea because neither side expects a NAT to sit between them for on-premises installations.

Inspect your network, and make it so that the phones can actually reach the PBX directly instead of going via NAT.

Keep it simple: have a single NIC on the server, and have the phones and server in the same subnet together on the same LAN.

 

[InHarmsWay]

So there is only 1 nic on this server and the phones are literally on the same LAN with no NAT between phones and the 3cx server. They will periodically show up and go away as well. The IP's of the server and the phones are all the same subnet. No hops at all.

 

[JohnS_3CX]

That sounds good, but still in this case, how do you account for seeing the phones registering from the gateway IP with duplicate entries?

Why is the traffic suddenly being NAT-ed via the gateway?

Is the PBX suddenly in some other network? or did you put a VPN/proxy on it perhaps?

The SIP server shows what it sees, so if you are seeing those entries there from the gateway IP something is clearly at play and you will have to investigate further to understand what causes this.