Figure 8: IPv6 Routing over TCP IPv4
The E Series router’s MP-BGP implementation uses BGP update messages to announce
the feasible routes to an associated IPv6 BGP next hop and also to announce the
nonfeasible routes that need to be withdrawn from the peer. The E Series router
announces only IPv6 global addresses as the BGP next-hop address; it does not use
the optional link-local IPv6 address as the BGP next hop.
BGP determines the next-hop addresses to be announced by using the IPv4-compatible
IPv6 address. For example, the following table shows the translation of an IPv4
address.
IPv6 addressIPv4 address
::10.1.1.110.1.1.1
When a BGP speaker receives a BGP update message carrying IPv6 feasible routes,
the speaker resolves the announced IPv6 BGP next hop by performing a route lookup
to the IPv6 address in the IPv6 route table.
Exchange of IPv6 Routing Information over TCP IPv6
Figure 9 on page 13 illustrates the exchange of IPv6 routing information over a TCP
IPv6 connection.
Figure 9: IPv6 Routing over TCP IPv6
Link-Local Next Hops in MP-BGP Packets
When the router has an external directly connected (non-multihop) BGP peer, the
router advertises two next hops. It advertises the global next hop and a next hop
with a link-local address. The link-local next hop is advertised even when the router
has been configured with the next-hop self feature. Advertising the link-local next
hop enables the configuration of single-hop EBGP sessions for IPv6 next hops.
For all other types of peers, the router advertises only the global BGP IPv6 next hop.
You can overwrite the global and link-local IPv6 next-hop addresses by configuring
and applying a route map that sets the addresses. The set ipv6 next-hop clause in
Overview â– 13
Chapter 1: Configuring BGP Routing
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