Cisco ASR 9000 Series Configuration Manual page 83

Implementing BGP
Topology
A sample topology to illustrate the configuration used in this section is shown in the following figure.
Figure 9: BGP Selective Multipath
Router R4 receives parallel paths from Routers R1, R2 and R3 to the same destination. If Routers R1 and R2
are configured as selective multipath neighbors on Router R4, only the parallel paths from these routers are
installed in the routing table of Router R4.
Configuration
Note Configure your network topology with iBGP/eBGP running on your routers, before configuring this
feature.
To configure BGP selective multipath on Router R4, use the following steps.
1 Configure Router R4 to accept selective multiple paths in your topology.
/* To configure selective multipath for iBGP/eBGP
RP/0/RSP0/CPU0:router(config)# router bgp 1
RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router(config-bgp-af)# maximum-paths ibgp 4 selective
RP/0/RSP0/CPU0:router(config-bgp-af)# maximum-paths ebgp 5 selective
RP/0/RSP0/CPU0:router(config-bgp-af)# commit
/* To configure selective multipath for eiBGP
RP/0/RSP0/CPU0:router(config)# router bgp 1
RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router(config-bgp-af)# maximum-paths eibgp 6 selective
RP/0/RSP0/CPU0:router(config-bgp-af)# commit
2 Configure neighbors for Router R4.
Routers R1 (1.1.1.1) and R2 (2.2.2.2) are configured as neighbors with the multipath option.
Router R3 (3.3.3.3) is configured as a neighbor without the multipath option, and hence the routes from
this router are not eligible to be chosen as multipaths.
RP/0/RSP0/CPU0:router(config-bgp)# neighbor 1.1.1.1
RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# multipath
RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# commit
OL-30423-03
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
BGP Selective Multipath
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