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From: Sina Mirtorabi (sina_at_CISCO.COM)
Date: Sat Nov 30 2002 - 09:32:50 CST
Vishwas> >> why we cannot have global addresses as next hop.
Acee> > You are guarenteed to have a link local address on all OSPFv3
Acee> > interfaces while there is no guarentee that you have a
Acee> global address.
Acee> > I believe this is the rationale for using the link local.
Vishwas> I agree to the fact that all IPv6(not OSPFv3 in context of the
Vishwas> discussion;-)) interfaces will have link-local addresses,
Vishwas> besides I am ok with the fact of using Link-local addresses
Vishwas> for nexthop. However I think saying that nexthops "will" be
Vishwas> link-local addresses would be wrong, we can have global
Vishwas> addresses in Link-LSA's and as nexthop(also the reason below)
having global address in Link-LSA is irrelevant to next hop calculation,
the fact of carrying global IPv6 address in Link-LSA is just related to
announcing all global Ipv6 address of a multi-access link to DR so that
it will announce them in its intra-area-prefix LSA
Link-local address is the only address to be always available ( as Acee
said ) therefore this address can always be used to reach your nexthop
and you should not need any other address even a node can have multiple
Vishwas> >> Besides for some conditions
Vishwas> >> of redistribution we may require global scope addresses
Vishwas> for nexthop.
If you are referring to FA setting, although if it is necessary to have
a global Ipv6 address for FA setting this address is only used to
forward a packet to, but this does Not mean that the nexthop is the FA.
A router while trying to install a route to the external with FA set
needs to just know its nexthop which would be a link-local address (
even if the ASBR setting the FA is directly connected to this router )