Subject: IPv6 link-local address added as NH

From: Nicolas REBIERRE <[email-masked]>
Date: Wed, 16 Oct 2002 14:55:39 +0200

Hi all,

I do not understand why is it necessary to add a link-local address on
the NH in some cases as specified in the RFC 2545 "MP-BGP for IPv6".
What is the difference between adding a route with a ll@ as next hop in
the Routing database and adding one with a global address as NH ?

Thanks,

Christophe.

[Please note I'm posting this mail on behalf of Christophe, whose posts
seem not to appear on the mailing list.]

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From: Pedro Roque Marques <[email-masked]>
Date: Wed, 16 Oct 2002 10:16:19 -0700 (PDT)

Nicolas REBIERRE writes:

> Hi all, I do not understand why is it necessary to add a link-local
> address on the NH in some cases as specified in the RFC 2545 "MP-BGP
> for IPv6".  What is the difference between adding a route with a ll@
> as next hop in the Routing database and adding one with a global
> address as NH ?

If you have a multi-access interface, ipv6 implicitly requires you to
install routes with a link-local address nexthop. This because, if
hosts are present on the same link, you might need to send an icmp
redirect message, which may only be sent in terms of a link local
address.

Since in BGP you don't want to know what are the characteristics of the
link, the link-local address is exchanged between directly connected
peers regardless of the link type.

regards,
  Pedro.