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500 Internal Server Error - lower CSeq on every new registration


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Hi there, I've been struggling with adding a SIP trunk to a different branch using a different PBX, it authenticates successfully the first time and then after some time fails with "500 Internal Server Error", I have contacted support for the other office's PBX and here is their response. Would appreciate any help with this!


"The registration produces those "500 Internal Server Error" errors because the CSeq of every new registration session is lower than that stored on last successful registration. The equipment which tries to register sends lower CSeq on every new registration, please check why it is doing so and if there is some configuration to change this behavior.


The cite from RFC.


RFC 3261

10.3. Processing REGISTER Requests


When receiving a REGISTER request, a registrar follows these steps:



... the registrar checks whether

the Call-ID agrees with the value stored for each binding. If

not, it MUST remove the binding. If it does agree, it MUST

remove the binding only if the CSeq in the request is higher

than the value stored for that binding. Otherwise, the update

MUST be aborted and the request fails."


So is there a setting on the Trunk page that could fix this? Thank you very much!

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