Cisco ASR 9000 Series Configuration Manual page 149

Implementing BGP
Command or Action
Step 4
bgp router-id ip-address
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf)# bgp
router-id 172.16.9.9
Step 5
label mode per-ce
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf)# label
mode per-ce
Step 6
address-family { ipv4 | ipv6 } unicast
Example:
RP/0/RSP0/CPU0:router(config-vrf)#
address-family ipv4 unicast
Step 7 network { ip-address / prefix-length | ip-address
mask }
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf-af)#
network 172.16.5.5/24
Step 8 aggregate-address address / mask-length
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf-af)#
aggregate-address 10.0.0.0/24
OL-30423-03
Purpose
Configures a fixed router ID for a BGP-speaking router.
Specifies either an IPv4 or IPv6 address family unicast and enters
address family configuration submode.
To see a list of all the possible keywords and arguments for this
command, use the CLI help (?).
Originates a network prefix in the address family table in the VRF
context.
Configures aggregation in the VRF address family context to
summarize routing information to reduce the state maintained in
the core. This summarization introduces some inefficiency in the
PE edge, because an additional lookup is required to determine
the ultimate next hop for a packet. When configured, a summary
prefix is advertised instead of a set of component prefixes, which
are more specifics of the aggregate. The PE advertises only one
label for the aggregate. Because component prefixes could have
different next hops to CEs, an additional lookup has to be
performed during data forwarding.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
Configuring a VPN Routing and Forwarding Instance in BGP
• Configures the per-CE label allocation mode to avoid an
extra lookup on the PE router and conserve label space
(per-prefix is the default label allocation mode). In this
mode, the PE router allocates one label for every immediate
next-hop (in most cases, this would be a CE router). This
label is directly mapped to the next hop, so there is no VRF
route lookup performed during data forwarding. However,
the number of labels allocated would be one for each CE
rather than one for each VRF. Because BGP knows all the
next hops, it assigns a label for each next hop (not for each
PE-CE interface). When the outgoing interface is a
multiaccess interface and the media access control (MAC)
address of the neighbor is not known, Address Resolution
Protocol (ARP) is triggered during packet forwarding.
• The per-vrf keyword configures the same label to be used
for all the routes advertised from a unique VRF.
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