Good to see the forum has caught up at last.
I was told by Yealink/Tiptel tech support here in Germany that the Yealink phones only support ipv6 in a DHCPv6 environment. I have to admit that I took this with a grain of salt, based on my own observations about these phones so far. We set up a DHCPv6 server, but never saw any DHCPv6 requests on the network. I did however see the phone sending out an IPv6 neighbour solicitation.
On a bit of a whim, I tried entering a static ipv6 fe80::1 link-local address. After rebooting the phone, I finally saw the first visible evidence that the firmware supported IPv6. However, instead of the LCD network status page showing the fe80::1 address I had entered, it had instead picked up a SLAAC-assigned 2001:... address (the ipv6 subnet advertised advertised on the LAN by our router). The phones had always picked up this address (and been pingable/browsable on that address), but had never displayed it in either the LCD panel, or the web UI, until after I had entered this static ipv6 fe80::1 address. The phones were also still not registering at this point.
I opened the phone web UI network config page (via ipv6 naturally), and removed the DNS server (ipv4) addresses. I could not save that form however, until I filled in a (ipv6) default gateway. I just entered the ipv6 address of our router. Upon rebooting, the phone finally registered via ipv6, and was able to make calls.
A couple of caveats / quirks:
- SRTP worked fine on both the SIP-T28P and SIP-T26P (as it had done with ipv4)
- TLS would not work on either phone over ipv6 (but did work over ipv4). It registered, but could not make calls, and I could see a icmpv6 port-unreachable in the packet trace. It then seemed to lose its registration... something a bit odd there
- Both phones would register, but not make calls when configured for SIP over TCP (non-TLS) - similar to the TLS problem
Going back to the network config page, the default gateway was again blank, but the static IP addr was still there (with the 2001:.. prefix). Basically, it had totally disregarded the fe80::1 address I had originally given it.
It also appears that the phones are not dual-stack (eg. ipv4 AND ipv6 simultaneously).
Seventh Signal Ltd. & Co. KG