Re: Last Call: <draft-ietf-6man-rfc4291bis-07.txt> (IP Version 6 Addressing Architecture) to Internet Standard

[Brian E Carpenter <[e-mail]>]

> 
>> 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
>>
>