ISP / 3CX issues

[MatthewShaw]

This could be either an ISP issue of an issue with our phone provider, my guess it's the former. I was wondering if anyone else has experience of the problem.

We have several schools using Talk-Straight as their ISP, Talk-Straight have a single VDOM that covers the trust. All was working fine until Tuesday, on Monday evening a new school joined the VDOM, since then niether the new school nor one other school have had consistent phone service.

The two schools that have issues both have an onsite PBX running 3CX, other schools are running cloud hosted 3CX and are not affected. The 2 affected school experience the same issue, incoming and local calls work, external calls ring but don't connect.

We have tried everything and now have a work-arround which involces routing calls to an external provider.

 

Has anyone else had this wissue with Talk-Straight and 3CX, was it resolved? and if so how?

 

Thanks

[Aprice]

Yes, we had issues with another phone system (PBXact) with talkstraight.

Problem turned out to be their GRE tunnel reducing the MTU size, which then caused fragmentation of the SIP packets leading to inconsistent problems establishing calls.

In the end we managed to get them to bypass the GRE tunnel for SIP / RTP so it didn't suffer the same problem.

 

Took a lot of work to get there in the end, did also end up ditching them in the end and putting a smoothwall in with a different provider.

[MatthewShaw]

Thanks, I've been so focused on routing/ALG I didn't consider packet sizing.

[ChetterHummin]

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