I have a client who has their PBX server offsite. They have two extensions at their office. It works perfectly. Their provider is Cox internet. Even though they have a dynamic IP, it hasn’t changed in years. They decided to change to Allo which is a fiber internet company. I was reading that they use a CGNAT. Will their phones still work with this new company?
Is this just the “extension”, or is the PABX also behind CGNAT? The latter case is likely to be difficult. the former case can break, if the extension doesn’t volunteer media. It will also be dependent on their being some activity on the signalling channel sufficiently often that the same addresses, as used in the registration, continue to be used.
Generally it is something best avoided, and if you can’t avoid it, you should test for the actual service and make sure that you use a short qualify interval, and enable keep alives.