BGP Split Horizon Lab
BGP Split Horizon rule
iBGP will not transfer prefix that it got from iBGP neighbor
BGP Split Horizon Lab
R2
interface Ethernet1
no switchport
ip address 192.168.23.2/24
!
interface Ethernet2
no switchport
ip address 192.168.24.2/24
!
interface Loopback0
ip address 2.2.2.2/24
ip routing
!
router bgp 1
neighbor 192.168.23.3 remote-as 1
network 2.2.2.0/24
R2#show ip bgp
BGP routing table information for VRF default
Router identifier 2.2.2.2, local AS number 1
Route status codes: * - valid, > - active, # - not installed, E - ECMP head, e P
S - Stale, c - Contributing to ECMP, b - backup, L - labelet
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Lp
Network Next Hop Metric LocPref Weight Path
* > 2.2.2.0/24 - 1 0 - i
R2#
R2#show ip bgp sum
BGP summary information for VRF default
Router identifier 2.2.2.2, local AS number 1
Neighbor Status Codes: m - Under maintenance
Neighbor V AS MsgRcvd MsgSent InQ OutQ Up/Down State PfxRcd PfxAcc
192.168.23.3 4 1 18 19 0 0 00:14:16 Estab 0 0
R2#
R3
interface Ethernet1
no switchport
ip address 192.168.34.3/24
!
interface Ethernet2
no switchport
ip address 192.168.23.3/24
!
interface Loopback0
ip address 3.3.3.3/24
router bgp 1
neighbor 192.168.23.2 remote-as 1
neighbor 192.168.34.4 remote-as 1
R3(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 3.3.3.3, local AS number 1
Route status codes: * - valid, > - active, # - not installed, E - ECMP head, e - ECMP
S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop
Network Next Hop Metric LocPref Weight Path
* > 2.2.2.0/24 192.168.23.2 0 100 0 i
R3(config-router-bgp)#show ip bgp sum
BGP summary information for VRF default
Router identifier 3.3.3.3, local AS number 1
Neighbor Status Codes: m - Under maintenance
Neighbor V AS MsgRcvd MsgSent InQ OutQ Up/Down State PfxRcd PfxAcc
192.168.23.2 4 1 20 19 0 0 00:15:40 Estab 1 1
192.168.34.4 4 1 18 18 0 0 00:14:19 Estab 0 0
R4
interface Ethernet1
no switchport
ip address 192.168.34.4/24
!
interface Ethernet2
no switchport
ip address 192.168.24.4/24
!
interface Loopback0
ip address 4.4.4.4/24
!
router bgp 1
neighbor 192.168.34.3 remote-as 1
R4(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 4.4.4.4, local AS number 1
Route status codes: * - valid, > - active, # - not installed, E - ECMP head, e - ECMP
S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop
Network Next Hop Metric LocPref Weight Path
R4(config-router-bgp)#show ip bgp sum
BGP summary information for VRF default
Router identifier 4.4.4.4, local AS number 1
Neighbor Status Codes: m - Under maintenance
Neighbor V AS MsgRcvd MsgSent InQ OutQ Up/Down State PfxRcd PfxAcc
192.168.34.3 4 1 19 19 0 0 00:15:40 Estab 0 0
R4(config-router-bgp)#