Android SIP and Asterisk: Unused IP assigned

Good day,
Been ‘hobbying’ with a small Asterisk server on a raspi. it is totally LAN based. Same subnet and the lots.
both hosts are ’ dynamic’ both users.conf data is the same except the username.

Most things work as expected. Partly because of this forum.

There is one thing though that i don’t understand. Without uploading error-logs and the lots, I wonder how the following ‘flow’ is possible

  • at startup asterisk everything OK. both Android SIP phones fully operational.
  • at some point, the SIP phones and/or Asterisk tries to re-register the phones

One phone (HUAWEI) keeps on working. The other phone (SAMSUNG) displays strange behavior:

– Registered SIP ‘SAMSUNG’ at
– Registered SIP ‘SAMSUNG’ at

Sometimes, Virtually at the same moment it gets assigned a * non existing non pingable IP-address *
The non-pingable IP addresses were, according to my router, in the past assigned to android phones without any SIP functionality installed. The phones are at present not within the network or switched off and definitely NOT binded/statically assigned by or in my router.

Both phones use exactly the same SIP program. That is sure. I wrote it :-))

Result is…the Samsung is not reachable after the first or maybe second re-register.


  • Any of you heard similar behavior before ?
  • Is the assignment of the non existing IP address done on the client side (Android OS or maybe even within an android wrapper…) or the server side (Asterisk, OS) or maybe even the router (?).
  • any direction in where to look… :-))
  • something obvious I overlook ?

Hope you want to join this puzzle.


Set up a packet capture and look at the difference in the two REGISTER attempts.

Something will have changed on the second attempt with the new IP, Likely the Contact.

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