Of couse "over radio" is not the same thing as "over AX.25"... These days, radio links on our net-44 network are mostly/all WiFi links and they would have no issue with IPv6. AX.25 and IPv6 have other incompatibilities than ARP. The minimum MTU requirement and the concern about efficiency at low bitrates are other things to worry about. But what is mainly holding me back to deploy IPv6 now is: - double effort of network administration for dual-stack - limited support in our favourite routers (MikroTik) - lack of immediate need, because we have not run out of IPv4 space and can still assign usable subnets to everyone who wants them (so no NAT required) So while I do have IPv6 deployed here at home, I while I don't rule out the deployment of IPv6 on our radio network, I don't consider it a high-priority thing. When doing it, I would get a /48 from our ISP, and then make a 1:1 mapping between already assigned IPv4 addresses within 44.137.0.0/16 and /64 nets within that space. So everyone who has a single address gets a corresponding /64 net and everyone who has a /28 subnets gets a /60 from that, without requiring any mechanism other than a simple document explaining the mapping. All places where IPv4 addresses and networks have been configured would get the corresponding IPv6 address. Probably I would go with encoding callsigns and service names into the lower 64 bits as proposed by Daniel EA4GPZ. And for distributing a "list of valid prefixes" amongst those that would like to be able to classify addresses as "within AMPRnet" or "outside AMPRnet" (now done by checking for 44.0.0.0/8, which of course does not really work as Brian Kantor already mentioned), I would propose setting up multihop BGP peering using private AS numbers between gateway hosts that want to advertise (and receive) the list of prefixes. But again, it is not on my list of things to do this year. Keeping everyone focused on building a working and expanding IPv4 network is more important, IMHO. Rob