DETAILED STEPS
PurposeCommand or Action
configure
Step 1
Specifies the BGP AS number and enters the BGP configuration mode,
allowing you to configure the BGP routing process.
router bgp as-number
Example:
RP/0/RSP0/CPU0:router(config)#router
bgp 100
Step 2
Enables the validity states of BGP paths to affect the path's preference in
the BGP best path process. This configuration can also be done in router
BGP address family submode.
bgp bestpath origin-as use validity
Example:
RP/0/RSP0/CPU0:router(config-bgp)#bgp
bestpath origin-as use validity
Step 3
Allows all "invalid" paths to be considered for BGP bestpath computation.
This configuration can also be done at global address family,
neighbor, and neighbor address family submodes. Configuring
bgp bestpath origin-as allow invalid in router BGP and address
family submodes allow all "invalid" paths to be considered for
BGP bestpath computation. By default, all such paths are not
bestpath candidates. Configuring bgp bestpath origin-as allow
invalid in neighbor and neighbor address family submodes allow
all "invalid" paths from that specific neighbor or neighbor address
family to be considered as bestpath candidates. The neighbor must
be an eBGP neighbor.
Note
bgp bestpath origin-as allow invalid
Example:
RP/0/RSP0/CPU0:router(config-bgp)#bgp
bestpath origin-as allow invalid
Step 4
This configuration takes effect only when the bgp bestpath origin-as
use validity configuration is enabled.
commit
Step 5
BGP 3107 PIC Updates for Global Prefixes
The BGP 3107 PIC Updates for Global Prefixes feature supports Prefix Independent Convergence (PIC)
updates for global IPv4 and IPv6 prefixes in an MPLS VPN provider network. This feature is based on RFC
3107 that describes using BGP to distribute MPLS labels for global IPv4 or IPv6 prefixes. This enables IGP
to scale better and also provides PIC updates for fast convergence.
RFC 3107 enables routes and labels to be carried in BGP. When BGP is used to distribute a particular route,
it can also be used to distribute an MPLS label that is mapped to that route. The label mapping information
for a particular route is piggybacked in the same BGP Update message that is used to distribute the route
itself. RFC 3107 allows filtering of Next-Hop Loops from OSPF and reduces labels advertised by LDP. This
implementation significantly reduces OSPF and LDP database.
The 3107 PIC implementation supports the following address-families with additional-path configuration.
•
address-family ipv4 unicast
•
address-family ipv6 unicast
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
OL-30423-03 69
Implementing BGP
BGP 3107 PIC Updates for Global Prefixes
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