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 configured (syntax is the same for IOS and XR. It 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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