Re: [NDP] Router autoconfiguration with RS/RA

Alexandru Petrescu <alexandru.petrescu@gmail.com> Fri, 06 June 2008 21:21 UTC

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Date: Fri, 06 Jun 2008 23:20:00 +0200
From: Alexandru Petrescu <alexandru.petrescu@gmail.com>
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To: Silviu VLASCEANU <silviu.vlasceanu@gmail.com>
Subject: Re: [NDP] Router autoconfiguration with RS/RA
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Silviu VLASCEANU wrote:
> I thank you both for the quick reaction. I generally agree. However, I 
> have some inline comments.
> 
> 2008/6/6 Hemant Singh (shemant) <shemant@cisco.com 
> <mailto:shemant@cisco.com>>:
> 
>     Silviu,
>      
>     A router can receive an RA on the router's upstream and use this RA
>     to autoconfigure the ipv6 address on interface(s) of the router.
>     Such a router interface configuration is no different from how a
>     host interface statelessly autoconfigures as per ND RFC 4861 and 4862. 
> 
> 
> I agree and I also thought that this should be possible.

What do you mean it _should_?  Do you want to write an implementation 
that should do it?  DO you want to modify the rfc?

>     However, ND RFC's do not mandate what does a router implementation
>     do for sending RA, configuring network prefixes in the router
>     downstream direction - these are conceptual variables that a router
>     vendor is left to do what they want to do.
> 
> 
> Noticed that too :)

Well I think RFCs tell very well how a router should send RAs, and they 
also say clearly a router shouldn't use the received RA to 
auto-configure a global address bases on the prefix in it.

Or has this changed recently?

>     As to answering your question which was:
>      
>     "Why wouldn't a router be authorized to send Router Sollicitation
>     messages?"
> 
> 
> My question was related to sending Router Sollicitations on the upstream 
> interface.

What does the RFC say?  Can a router send an RS?

>     here is my reply.
>      
>     As far as the interface on the router has no RA configured, and the
>     interface is configuring an IPv6 address using stateless
>     autoconfiguration or even manual configuration, this interface is OK
>     to send an RS in the router downstream. 
> 
> 
> As I understand, a router could configure its "downstream" interfaces by 
> RAs received from other routers in the "downstream". Is it correct?

I don't think it's correct.

> This way, the notion of up/downstream would loose its sense.

I think RFCs don't use the terms up/downstream at all, no distinguishing 
between them usually.

Alex


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