Re: [NDP] Router autoconfiguration with RS/RA

[Alexandru Petrescu <alexandru.petrescu at gmail.com>]

Ole Troan wrote:
> 2008/6/6 Alexandru Petrescu <alexandru.petrescu at gmail.com>:
>> Hemant Singh (shemant) wrote:
>>> Silviu,
>>> 
>>> A router can receive an RA on the router's upstream
>> Yes it can.  It uses it to report whether some things went wrong, 
>> log stuff, but don't act.
>> 
>>> and use this RA to autoconfigure the ipv6 address on interface(s)
>>>  of the router.
>> Usually no, it can not.  A particular case of a Mobile Router away 
>> from home can auto-configure an address on its egress interface 
>> with stateless autoconf.  But a non-mobile router (not implementing
>>  rfc3963) can't and it shouldn't.
>> 
>> A router is something that forwards packets.  A linux router can't
>>  auto-configure an address once one sets the forwarding=1.  A Cisco
>>  router I have doubts, but it doesn't mean it follows rfc.
> 
> a router can very well have an interface configured in host mode 
> where it uses normal host configuration mechanisms. [...] I don't see
>  any reason why it couldn't also do forwarding on this interface.

Ok, but what does the RFC say?  Can a non-mobile router configure one of 
its interface in host mode, auto-configure an address from received RA 
on it, and still forward packets to/from that interface?

> router/host mode is a per interface property.

Well, I don't think a non-mobile router can have any one of its 
interfaces in 'host' mode - once at least one interface is in host mode 
it will no longer forward packets between any of its other interfaces.

> and has been said before the RS/RA mechanism for router 
> discovery/prefix discovery does not support prefix delegation.

Right...

> of course you can invent a new protocol using RS/RA messages to do 
> it, but I haven't seen any convincing reason why we should.

I agree.

> note that the DHCP PD was triggered by a draft proposing using ICMP
> for PD. we suggested using DHCP instead, since one eventually would
> have reinvented lots of the DHCP machinery to make it work.

A-ha.

Alex


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