BGP Processing of Received Routes
BGP processes received routes differently depending on whether the route is labeled
or unlabeled, unicast or VPN.
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 64 on page 460 summarizes indirect next hop resolution.
Table 64: Resolution of Indirect Next Hops
Table in Which BGP Indirect Next Hop ResolvesRoute Type
IP routing tableUnlabeled unicast
IP tunnel routing table, IP routing tableLabeled unicast
460 â– Configuring BGP VPN Services
JUNOSe 11.1.x BGP and MPLS Configuration Guide
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