BGP Accumulative IGP Metric

R1(config-router-bgp)#show ip bgp 6.6.6.6
BGP routing table information for VRF default
Router identifier 1.1.1.1, local AS number 123
BGP routing table entry for 6.6.6.6/32
 Paths: 2 available
  456
    2.2.2.2 from 2.2.2.2 (2.2.2.2)
      Origin IGP, metric 0, localpref 100, IGP metric 20, weight 0, received 00:00:07 ago, valid, internal, best
      Rx SAFI: Unicast
  456
    3.3.3.3 from 3.3.3.3 (3.3.3.3)
      Origin IGP, metric 0, localpref 100, IGP metric 40, weight 0, received 00:00:29 ago, valid, internal
      Rx SAFI: Unicast

The path through R4 = 20 + 10 + 10 = 40 The path through R5 = 10 + 30 + 10 = 50 best path through R5 (though R4 is better)

R6#show ip bgp 1.1.1.1
BGP routing table information for VRF default
Router identifier 6.6.6.6, local AS number 456
BGP routing table entry for 1.1.1.1/32
 Paths: 2 available
  123
    5.5.5.5 from 5.5.5.5 (5.5.5.5)
      Origin IGP, metric 0, localpref 100, IGP metric 20, weight 0, received 00:06:49 ago, valid, internal, best
      Rx SAFI: Unicast
  123
    4.4.4.4 from 4.4.4.4 (4.4.4.4)
      Origin IGP, metric 0, localpref 100, IGP metric 30, weight 0, received 20:59:03 ago, valid, internal
      Rx SAFI: Unicast
R6#

On Arista AIGP is available only in multi-agent mode

service routing protocols model multi-agent

Start Config R1

interface Ethernet1
   no switchport
   ip address 192.168.12.1/24
   ip ospf cost 10
!
interface Ethernet2
   no switchport
   ip address 192.168.13.1/24
   ip ospf cost 30
!
interface Loopback0
   ip address 1.1.1.1/32
   ip ospf cost 10
!
ip routing
!
router bgp 123
   neighbor 2.2.2.2 remote-as 123
   neighbor 2.2.2.2 update-source Loopback0
   neighbor 3.3.3.3 remote-as 123
   neighbor 3.3.3.3 update-source Loopback0
   network 1.1.1.1/32
!
router ospf 1
   network 1.1.1.1/32 area 0.0.0.0
   network 192.168.12.0/24 area 0.0.0.0
   network 192.168.13.0/24 area 0.0.0.0

interface Ethernet1
   no switchport
   ip address 192.168.12.2/24
   ip ospf cost 10
!
interface Ethernet2
   no switchport
   ip address 192.168.24.2/24
!
interface Loopback0
   ip address 2.2.2.2/32
   ip ospf cost 10
!
ip routing
!
router bgp 123
   neighbor 1.1.1.1 remote-as 123
   neighbor 1.1.1.1 next-hop-self
   neighbor 1.1.1.1 update-source Loopback0
   neighbor 3.3.3.3 remote-as 123
   neighbor 3.3.3.3 next-hop-self
   neighbor 3.3.3.3 update-source Loopback0
   neighbor 192.168.24.4 remote-as 456
!
router ospf 1
   network 2.2.2.2/32 area 0.0.0.0
   network 192.168.12.0/24 area 0.0.0.0

interface Ethernet1
   no switchport
   ip address 192.168.13.3/24
   ip ospf cost 30
!
interface Ethernet2
   no switchport
   ip address 192.168.35.3/24
!
interface Loopback0
   ip address 3.3.3.3/32
   ip ospf cost 10
!
ip routing
!
router bgp 123
   neighbor 1.1.1.1 remote-as 123
   neighbor 1.1.1.1 next-hop-self
   neighbor 1.1.1.1 update-source Loopback0
   neighbor 2.2.2.2 remote-as 123
   neighbor 2.2.2.2 next-hop-self
   neighbor 2.2.2.2 update-source Loopback0
   neighbor 192.168.35.5 remote-as 456
!
router ospf 1
   network 3.3.3.3/32 area 0.0.0.0
   network 192.168.13.0/24 area 0.0.0.0

interface Ethernet1
   no switchport
   ip address 192.168.24.4/24
!
interface Ethernet2
   no switchport
   ip address 192.168.46.4/24
   ip ospf cost 20
!
interface Loopback0
   ip address 4.4.4.4/32
   ip ospf cost 10
!
ip routing
!
router bgp 456
   neighbor 5.5.5.5 remote-as 456
   neighbor 5.5.5.5 next-hop-self
   neighbor 5.5.5.5 update-source Loopback0
   neighbor 6.6.6.6 remote-as 456
   neighbor 6.6.6.6 next-hop-self
   neighbor 6.6.6.6 update-source Loopback0
   neighbor 192.168.24.2 remote-as 123
!
router ospf 1
   network 4.4.4.4/32 area 0.0.0.0
   network 192.168.46.0/24 area 0.0.0.0

interface Ethernet1
   no switchport
   ip address 192.168.24.4/24
!
interface Ethernet2
   no switchport
   ip address 192.168.46.4/24
   ip ospf cost 20
!
ip routing
!
router bgp 456
   neighbor 5.5.5.5 remote-as 456
   neighbor 5.5.5.5 next-hop-self
   neighbor 5.5.5.5 update-source Loopback0
   neighbor 6.6.6.6 remote-as 456
   neighbor 6.6.6.6 next-hop-self
   neighbor 6.6.6.6 update-source Loopback0
   neighbor 192.168.24.2 remote-as 123
!
router ospf 1
   network 4.4.4.4/32 area 0.0.0.0
   network 192.168.46.0/24 area 0.0.0.0

interface Ethernet1
   no switchport
   ip address 192.168.46.6/24
   ip ospf cost 20
!
interface Ethernet2
   no switchport
   ip address 192.168.56.6/24
   ip ospf cost 10
!
interface Loopback0
   ip address 6.6.6.6/32
   ip ospf cost 10
!
ip routing
!
router bgp 456
   neighbor 4.4.4.4 remote-as 456
   neighbor 4.4.4.4 update-source Loopback0
   neighbor 5.5.5.5 remote-as 456
   neighbor 5.5.5.5 update-source Loopback0
   network 6.6.6.6/32
!
router ospf 1
   network 6.6.6.6/32 area 0.0.0.0
   network 192.168.46.0/24 area 0.0.0.0
   network 192.168.56.0/24 area 0.0.0.0

Arista special behavior

BGP MED