Error "WAN Block is On" when registering Grandstream phones with on-premise 3CX

[MAGTEL SYSTEMS]

Hi everyone,

I’m facing an issue while trying to register new Grandstream phones with our on-premise 3CX system. The error I’m getting is "WAN Block is On". Both the 3CX server and the phones are on the same network, so I’m not sure why this is happening.

Has anyone encountered this issue before? Any suggestions on how to resolve it?

Here’s what I’ve checked so far:

The 3CX server and phones are on the same subnet.

 

[JohnS_3CX]

On premise means the system and the phones are on the same LAN (RFC1918 compliant addressing).
If they are not, the system sees them as external and blocks them for security.

You also need to have Split DNS pointing your FQDN to the PBX local IP, otherwise the phones will try to reach it from the internet, and hence get blocked. https://www.3cx.com/blog/releases/split-dns-on-prem/

 

[MAGTEL SYSTEMS]

phones are using local 3cx ip for registering the phones. not fqdn address

 

[JohnS_3CX]

Then either you are not on the same LAN as previously thought, or the IPs are not in the private range perhaps.
They should be in these ranges to be considered local:

10.0.0.0/8 (10.0.0.0 - 10.255.255.255)
172.16.0.0/12 (172.16.0.0 - 172.31.255.255)
192.168.0.0/16 (192.168.0.0 - 192.168.255.255)

 

[MAGTEL SYSTEMS]

OUR LOCAL LAN IS 50.0.1.0 /24 . HOW WE CAN SOLVE THIS PROBLEM

 

[SteveITS]

OUR LOCAL LAN IS 50.0.1.0 /24 . HOW WE CAN SOLVE THIS PROBLEM

That's a public block. The "correct" solution would be to change your LAN to a private IP/RFC1918 range. If it helps I have heard over the years of other software detecting itself as a public/private IP based on its IP range, as well, so you may eventually encounter other similar problems.