IOS vs XR: AIGP

Scenario
The AIGP (Accumulated IGP) metric, if it is being sent and if the receiver is configured to take it into consideration, is evaluated immediately after local preference. If multiple paths for a prefix are received, some with AIGP and some without, the prefixes without AIGP will be ignored unless bgp bestpath igp ignore is configure (syntax is the same for IOS and XR is a global BGP command).

The below diagram shows a scenario whereby AIGP is configured for both eBGP and iBGP peers from the point of view of R1.

More details on AIGP can be found here.


IOS Config

router bgp 100
bgp router-id 172.16.1.1
bgp log-neighbor-changes
no bgp default ipv4-unicast
neighbor 2001:DB8:1::2 remote-as 200
neighbor 2001:11:22::2 remote-as 200
neighbor 2001:11:22::2 update-source Loopback0
neighbor 10.1.1.2 remote-as 200
neighbor 172.16.1.2 remote-as 100
neighbor 172.16.1.2 update-source Loopback0
!
address-family ipv4
redistribute connected route-map REDISTRIBUTE-CONNECTED
neighbor 40.60.27.2 activate
! the AIGP command is needed to send and receive AIGP metrics
neighbor 40.60.27.2 aigp
neighbor 172.16.6.6 activate
neighbor 172.16.6.6 aigp
neighbor 172.16.6.6 next-hop-self
exit-address-family
!
address-family ipv6
redistribute connected route-map REDISTRIBUTE-CONNECTED
2001:DB8:1::2 activate
2001:DB8:1::2 aigp
neighbor 2001:11:22::2 activate
neighbor 2001:11:22::2 aigp
neighbor 2001:11:22::2 next-hop-self
exit-address-family
!
route-map REDISTRIBUTE-CONNECTED permit 10
set aigp-metric igp-metric
!

XR Config

route-policy REDISTRIBUTE-CONNECTED
set aigp-metric igp-cost
end-policy
!
router bgp 100
bgp log neighbor changes detail
bgp router-id 172.16.1.1
address-family ipv4 unicast
redistribute connected route-policy REDISTRIBUTE-CONNECTED
!
address-family ipv6 unicast
redistribute connected route-policy REDISTRIBUTE-CONNECTED
!
neighbor 10.1.1.2
remote-as 200
address-family ipv4 unicast
aigp
!
neighbor 172.16.1.2
remote-as 100
address-family ipv4 unicast
aigp
next-hop-self
!
neighbor 2001:DB8:1::2
remote-as 200
address-family ipv6 unicast
aigp
!
neighbor 2001:11:22::2
remote-as 100
address-family ipv6 unicast
aigp
next-hop-self
!
!

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