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JunosE 11.2.x BGP and MPLS Configuration Guide
BGP Advertising Rules for Labeled and Unlabeled Routes with the Same AFI
460
Labeled Unicast Routes
When BGP receives a labeled route from a directly connected peer, BGP uses the MPLS
major interface that is next to the peer IP interface to resolve the route's BGP next hop.
If the MPLS major interface exists and is up, then the next hop is reachable.
When the received labeled route is not from a directly connected peer, BGP attempts to
resolve the BGP indirect next hop of the route in the IP tunnel routing table. When the
BGP indirect next hop is reachable, BGP adds the route to both the IP routing table and
to the IP tunnel routing table. The route is added as a U-T (unicast-tunnel-usable) route.
Unlabeled Unicast Routes
When BGP receives an unlabeled route from a directly connected peer, the route's next
hop is resolved to the directly connected interface.
When the received unlabeled route is not from a directly connected peer, BGP resolves
the BGP indirect next hop of the route in the IP routing table. If the BGP indirect next hop
is reachable, BGP adds the route to the IP routing table as a U (unicast) route.
Resolving IPv6 Indirect Next Hops
When the address of the indirect next hop is an IPv4-mapped IPv6 address, BGP resolves
the indirect next hop in the IPv4 routing table and IPv4 tunnel routing table. When the
indirect next hop is a native IPv6 address, the indirect next hop is resolved in the IPv6
routing table and IPv6 tunnel routing table.
Labeled VPN Routes
In the core VRF, when BGP receives a BGP-labeled VPN route from a multihop VPN peer,
it attempts to resolve the BGP indirect next hop in the IP tunnel routing table. If the labeled
VPN route is received from a nonmultihop peer, then the BGP indirect next hop is always
resolved, because a connected route to that peer exists in the IP tunnel routing table.
Table 91 on page 460 summarizes indirect next hop resolution.
Table 91: Resolution of Indirect Next Hops
Route Type
Table in Which BGP Indirect Next Hop Resolves
Unlabeled unicast
IP routing table
Labeled unicast
IP tunnel routing table, IP routing table
Labeled VPN
IP tunnel routing table
When BGP receives a route to a prefix with the same AFI in both labeled and unlabeled
forms, only one of these routes can be selected as the best route. The action taken after
the best route is selected depends on whether the best route is labeled or unlabeled,
and on what SAFI was previously negotiated with peers other than the one from which
it received the best route. Table 92 on page 461 lists the advertising action taken for the
best route, whether labeled or unlabeled.
Copyright © 2010, Juniper Networks, Inc.
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