SIP setup - help please

Hello, here in the UK the provision of PSTN services via copper pair is coming to an end. My ISP also provides my PSTN service and want to send me a “chinese” modem so I can use VoIP. However I use a commecial grate router (Ubiquiti EdgeMax EdgeRouter Pro). The ISP has now relented and sent me the list of SIP settings so I can attemp to enter these into my FreePBX machine and negate the need for the “Chinese Router”. I would really appreciate some help in determining what setting to use in the Trunk/sip settings/Outgoing & Incoming. Here is the list sent to me by the ISP (ZEN Internet);

Setting Result
Provider Name Zen Internet
Country UK
Proxy or B2BUA, Media handling interface specification Proprietary proxy
Port 5060
Re-registration Interval at Provider (seconds) up to 900
Use Proxy? Yes
Port 5060 UDP
IP address *..7.228
Media Call Audio Addresses
Ports 20000 to 30000 UDP
IP Addresses: **..88.0/28 and **..88.16/28 or enter the addresses from **..88.0 to **..88.31 (inclusive) if your network equipment does not support representing IP ranges using CIDR
UDP Yes Port 5060
IPsec Tunnel No
G.711 a-law Yes Sample rate 20ms
G.711 -law Yes Sample rate 20ms
G.729A No
G.729A/B No
Fax G.711 Based Fax Yes
Fax T.38 No
RFC2833 Yes
Inband Yes
Security & Special Features
Authentication - Digest Authentication
Proxy or B2BUA, Media Handling - B2BUA
Forking Yes
Transfer with REFER No

Many thanks

A straightforward pjsip trunk setup should work. Try these settings as a start, report any problems.

pjsip General tab:
Username: (as shown on Zen portal)
Auth username: (if specified by Zen, otherwise leave blank)
Secret: (SIP password shown on Zen portal)
SIP Server:

pjsip Advanced tab:
Expiration: 900
Outbound Proxy: sip:\;lr\;hide
(replace with IP address or hostname shown for Proxy on Zen portal)
Contact User: phone number, matching DID number in your Inbound Route
From Domain:
From User: (same as you have for Username)

pjsip Codecs tab:
Only alaw and ulaw checked, alaw should come first.

Firewall: (as noted by Zen, though you’ll need other forwarding if you will have non-VPN remote extensions).

Hi Stewart,
Thanks for your help. I have entered the values you have recommended. However the connection is failing; here is the log file output.

[2023-09-12 09:42:56] WARNING[30684] res_pjsip_outbound_registration.c: Temporal response ‘401’ received from ‘’ on registration attempt to ‘sip:[email protected]:5060’, retrying in ‘60’
[2023-09-12 09:43:01] ERROR[30684] res_pjsip.c: Unable to create outbound OPTIONS request to endpoint ZEN_VoIP as URI ‘sip:zen416525@[email protected]’ is not valid
[2023-09-12 09:41:01] ERROR[30684] res_pjsip/pjsip_options.c: Unable to create request to qualify contact sip:zen416525@[email protected] on AOR ZEN_VoIP

Mnay thanks


I know nothing about Zen, but here are my guesses:

The hard 401 indicates that the server did not find the username/password combination to be valid. The SIP password is almost certainly different from the password you use to log into the Zen account. If the SIP password is something you set on their portal, choose one that is no more than 12 characters and consists only of letters and digits. Use copy/paste to ensure that Secret for the trunk is the same value.

If Zen assigns the SIP password, there might be an issue with special characters that need to be escaped. If this is the issue, their site may allow generation of a new password without the offending character.

Do you have some parameter(s) in your trunk set to ‘zen416525@zen’ ? If so, where did they specify that? It is likely valid for Auth username, but normally not elsewhere.

This may be easiest to resolve if you post a redacted version of their credentials documentation. Replace the password with ppppp and the username with uuuuu. If you feel that any other parameters are personal, redact them similarly, but use the same format.

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