> >> Maybe Linux is different. > > YEs in a sesne. I fired up a Linux box and tried ip -6 address add 2001:db8:dead::beef dev wlp2s0 It works - the /nn is not required - but the prefix length shown by ip -6 address show is /128, so that seems to be the Linux default. (Sorry, can't cut and paste from that screen to this one. Also I can't mess with the RAs since it is a shared gateway.) Regards Brian On 24/02/2017 00:57, Alexandre Petrescu wrote: > > > Le 22/02/2017 à 21:04, Brian E Carpenter a écrit : >> On 22/02/2017 22:41, Alexandre Petrescu wrote: >> <snip> >> >>>> Well that does two things: configures a 128 bit address (as Chris >>>> points out, *all* addresses are 128 bits, duh) and associates a >>>> prefix length with it, which afaik is optional. >>> >>> The prefix length is not optional. There is no system out there on >>> which one could configure a 128bit address without explicitely telling >>> '/128' or '/64' or '/something-else'. >> >> Wrong. Sorry to get all technical, but on Windows: > > Ok, I didnt know Windows acts that way. > >> >> C:\windows\system32>netsh interface ipv6 add address ? >> >> Usage: add address [interface=]<string> [address=]<IPv6 address>[/<integer>] >> [[type=]unicast|anycast] >> [[validlifetime=]<integer>|infinite] >> [[preferredlifetime=]<integer>|infinite] >> [[store=]active|persistent] >> [[skipassource=]true|false] >> >> The [/<integer>] looks pretty optional to me. > > I agree. > >> I just tried >> netsh interface ipv6 add address 12 2001:db8:dead::beef >> and now I have three addresses: >> >> C:\windows\system32>netsh interface ipv6 show addresses >> >> Interface 12: Wireless Network Connection >> >> Addr Type DAD State Valid Life Pref. Life Address >> --------- ----------- ---------- ---------- ------------------------ >> Manual Preferred infinite infinite 2001:db8:dead::beef >> Public Preferred 1h54m9s 54m9s fd63:45eb:dc14:0:28cc:dc4c:9703:6781 >> Other Preferred infinite infinite fe80::28cc:dc4c:9703:6781%12 >> >> When I try to ping 2001:db8:dead::cafe, I see what I expected in Wireshark: >> neighbour solicitations from 2001:db8:dead::beef to ff02::1:ff00:cafe. >> In other words, the new address is treated as on-link. I can't find any trace >> of an associated prefix entry. > > This looks strange. The NS for 2001:db8:dead::beef are normal - they > are DAD. But to consider it on-link, without having been told the plen > is /64 and the prefix, is not normal. > > I suppose Windows configures an address and a prefix/plen by receiving > an RA. And then, when adding manually an address it considers that > address to be part of that link too. That is not normal, because the > prefix 2001:db8 is certainly not the same as the one in the RA. > > I suppose Windows programmers made it so because they needed that > [/integer] to be optional but they also needed the addresses that are > manually configured to be part of some subnet... which one? > > To check this behaviour, one would silence the RAs, netsh restart, and > then manually configure an address without plen, and add a default gw. > Can that ping the gw? Can it ping the Internet? If yes, then it means > there is a /64 hidden somewhere that must be removed. If it does not > work, then it's good - it misses the plen. > >> Maybe Linux is different. > > YEs in a sesne. > > Alex > >> >> Brian >> >