[Xorp-users] IPv6 & BGP

[Atanu Ghosh]

>>>>> "Hasso" == Hasso Tepper <hasso@linux.ee> writes:

    Hasso> Mark Handley wrote:
    >> On 12/17/05, Kristian Larsson <kristian@juniks.net> wrote: > I'm
    >> having problem setting up a v6 only BGP > connection. it would
    >> seem it requires a next-hop > parameter which is v4. Since I
    >> don't have v4 on > this machine at all it is difficult.  > Please
    >> advice
    >> 
    >> The BGP spec requires a NEXTHOP attribute in all routes, and this
    >> is specified as an IPv4 address.  It needs this even if you're
    >> running IPv6 only, but it shouldn't be used for the routing
    >> calculation.  I've not tried it (probably Atanu has) but you
    >> should be able to specify 10.0.0.1 or something similar.

    Hasso> Sorry, but this is nonsense.

    Hasso> From draft-ietf-idr-rfc2858bis-07.txt (the same text is there
    Hasso> in the RFC2858 as well):

    Hasso> "An UPDATE message that carries no NLRI, other than the one
    Hasso> encoded in the MP_REACH_NLRI attribute, SHOULD NOT carry the
    Hasso> NEXT_HOP attribute.  If such a message contains the NEXT_HOP
    Hasso> attribute, the BGP speaker that receives the message SHOULD
    Hasso> ignore this attribute."

Actually this is not a protocol issue but a configuration issue. In the
configuration we have an IPv4 nexthop marked as a mandatory item. In the
case where you want to use BGP for IPv6 only we have no way of disabling
the check (yet). If you set the ipv4-unicast and ipv4-multicast flags to
false and you have no local IPv4 addresses then just choose a legal IPv4
address. The IPv4 nexthop address should *not* be used it just needs to
satisify the configuration constraint. I have never tried an IPv6
peering on a machine that does not have any IPv4 addresses configured
but I would expect it to work.

    Atanu.