FRITZ!Box 7590 AX (FRITZ!OS 8.25) rejects SIP REGISTER from ha-sip 5.6 (PJSIP 2.17), while Zoiper works

[forceman854]

I'm unable to register ha-sip against a FRITZ!Box 7590 AX running FRITZ!OS 8.25.

The same IP phone credentials work immediately with Zoiper, but ha-sip never successfully registers.

Environment
ha-sip: 5.6
Home Assistant OS: 17.3
Home Assistant Core: 2026.6.4
Supervisor: 2026.06.2
Hardware: Raspberry Pi 5
Architecture: aarch64
PJSIP: 2.17
Router: FRITZ!Box 7590 AX
FRITZ!OS: 8.25
SIP configuration
sip_global:
port: 5060
log_level: 5

sip:
enabled: true
registrar_uri: sip:192.168.178.1
id_uri: sip:HomeAssistant@192.168.178.1
realm: "*"
user_name: HomeAssistant
password: ****
answer_mode: listen

I also tested with:

realm: ""
registrar_uri: sip:fritz.box
UDP
TCP
ICE disabled
STUN disabled
Contact rewrite disabled

No difference.

FRITZ!Box configuration

An IP telephone is configured correctly.

Username: HomeAssistant
Incoming number assigned
Same credentials successfully register with Zoiper
Observed behaviour
UDP

ha-sip repeatedly sends REGISTER messages.

The FRITZ!Box never responds.

There is:

no 401 Unauthorized
no 403
no 200 OK
no entry in the FRITZ!Box telephone event log

Example:

REGISTER sip:192.168.178.1 SIP/2.0

Via: SIP/2.0/UDP ...
From: sip:HomeAssistant@192.168.178.1
To: sip:HomeAssistant@192.168.178.1
Contact: sip:HomeAssistant@192.168.178.59:5060;ob
TCP

TCP connection is established successfully:

TCP transport connected to 192.168.178.1:5060

ha-sip sends REGISTER:

REGISTER sip:192.168.178.1;transport=tcp SIP/2.0

Via: SIP/2.0/TCP ...

Supported: outbound, path

Contact:
sip:HomeAssistant@192.168.178.59:56939;transport=TCP;ob;
reg-id=1;
+sip.instance="urn:uuid:..."

Immediately afterwards the FRITZ!Box closes the TCP connection:

TCP connection closed

SIP registration failed
503 End of file (PJ_EEOF)

No SIP response is ever received.

Additional testing

Verified:

✅ Raspberry Pi can ping the FRITZ!Box
✅ Port 5060 reachable
✅ IP phone configured correctly
✅ Same credentials work with Zoiper
✅ UDP and TCP both tested
✅ ICE disabled
✅ STUN disabled
Question

Could this be related to PJSIP 2.17 generating REGISTER requests that are rejected by recent FRITZ!OS versions (8.25)?

The REGISTER generated by ha-sip contains:

Supported: outbound, path

Contact:
...;ob
reg-id=1
+sip.instance

Zoiper registers successfully against the same FRITZ!Box.

Any ideas would be appreciated.

[carsten862]

You must write the IP phone's name and username in lowercase; you cannot use any special characters or spaces. If you change this for an IP phone that has already been set up in the FRITZ!Box, it corrupts the FRITZ!Box's internal routing table. Therefore, you have to set up the IP phone again and follow the rules right from the start. Case sensitivity doesn't matter for the password. It took me hours to figure this out, and I’m not sure if it’s a bug. But as a German speaker, you naturally want to capitalize nouns—which isn't allowed here. I hope it works for you.

[forceman854]

Thanks for the tip about lowercase usernames! In my case it turned out to be a combination of several factors, but everything works now:

My setup (FRITZ!Box 7590 AX, FRITZ!OS 259.08.25, ha-sip 5.6):

Switched transport to TCP instead of UDP – my FritzBox was silently dropping UDP REGISTER requests (no 401, no response at all). Only after setting registrar_uri: sip:192.168.178.1;transport=tcp did I get any response.
Disabled ICE and several NAT-rewrite options via the account-level options field:
options: >
--ice disabled --use-stun-for-sip disabled --use-stun-for-media disabled
--use-contact-rewrite disabled
Set realm explicitly to fritz.box instead of the wildcard "*" or the IP address – my pjsip version (2.17) wasn't matching the credential against the realm returned by the server (can not find credential for fritz.box/Digest).

Your note about lowercasing the username was also helpful for making sure the registration goes through cleanly — thanks for sharing, saved me some additional troubleshooting!

[arnonym]

@carsten862 Thanks for helping out!
@forceman854 May this be closed?