We are working on changes to the source IP addresses used for SIP messages we send where we have authentication details to provide. The reason is that asterisk boxes cannot easily be configured to tell "peers" from "users" in order to decide if a challenge is needed. This has caused problems for customers using VoIP unauthenticated from our IPs and SIP2SIM authenticated as a user. The first stage of the change has been done today, and involves the source IPv6 addresses. For all authenticated IPv6 messages (i.e. those for which we expect a challenge) we are sending from 2001:8b0:0:30::5060:a000/116 whilst any unauthenticated are from 2001:8b0:0:30::5060::/116 As this is within the 2001:8b0:0:30::5060::/112 block we have advised for VoIP use, this should not need any firewall changes or config changes, but we are interested in any feedback on any issues encountered. The change for IPv4 will take a bit longer - as we are unsure if to try and free up space in the 81.187.30.110-119 range previously advised, or to allocate a new range for this. This only affects calls originating from the new "voiceless" servers, which includes all SIP2SIM, but affects all authenticated messages whether SIP2SIM or otherwise. Please let us know of any issues.