BGP Weight
hostname R1
!
interface Ethernet1
no switchport
ip address 192.168.12.1/24
!
interface Ethernet2
no switchport
ip address 192.168.13.1/24
!
interface Loopback0
ip address 1.1.1.1/24
!
ip routing
!
router bgp 1
router-id 1.1.1.1
neighbor 192.168.12.2 remote-as 2
neighbor 192.168.13.3 remote-as 2
hostname R2
!
interface Ethernet1
no switchport
ip address 192.168.12.2/24
!
interface Ethernet2
no switchport
ip address 192.168.23.2/24
!
interface Loopback0
ip address 2.2.2.2/24
!
interface Loopback1
ip address 22.22.22.22/24
!
ip routing
!
router bgp 2
router-id 2.2.2.2
neighbor 192.168.12.1 remote-as 1
neighbor 192.168.23.3 remote-as 2
network 2.2.2.0/24
hostname R3
!
interface Ethernet1
no switchport
ip address 192.168.13.3/24
!
interface Ethernet2
no switchport
ip address 192.168.23.3/24
!
interface Loopback1
ip address 22.22.22.22/24
!
ip routing
!
router bgp 2
router-id 3.3.3.3
neighbor 192.168.13.1 remote-as 1
neighbor 192.168.23.2 remote-as 2
network 2.2.2.0/24
192.168.12.2 wins as rid 2.2.2.2 smaller ther rid 3.3.3.3 (others attributes are equal)
R1(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 1.1.1.1, 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
* > 2.2.2.0/24 192.168.12.2 0 100 0 2 i
* 2.2.2.0/24 192.168.13.3 0 100 0 2 i
R1(config-router-bgp)#neighbor 192.168.13.3 weight 500
R1(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 1.1.1.1, 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
* > 2.2.2.0/24 192.168.13.3 0 100 500 2 i
* 2.2.2.0/24 192.168.12.2 0 100 0 2 i
R1(config-router-bgp)#
Let’s try with certain prefix
R2(config-if-Lo1)#router bgp 2
R2(config-router-bgp)#network 22.22.22.0/24
R3(config)#router bgp 2
R3(config-router-bgp)#network 22.22.22.0/24
R1(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 1.1.1.1, 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
* > 2.2.2.0/24 192.168.13.3 0 100 500 2 i
* 2.2.2.0/24 192.168.12.2 0 100 0 2 i
* > 22.22.22.0/24 192.168.13.3 0 100 500 2 i
* 22.22.22.0/24 192.168.12.2 0 100 0 2 i
1(config-router-bgp)#no neighbor 192.168.13.3 weight 500
R1(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 1.1.1.1, 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
* > 2.2.2.0/24 192.168.12.2 0 100 0 2 i
* 2.2.2.0/24 192.168.13.3 0 100 0 2 i
* > 22.22.22.0/24 192.168.12.2 0 100 0 2 i
* 22.22.22.0/24 192.168.13.3 0 100 0 2 i
Set weight for 22.22.22.0/24 prefix
ip prefix-list 22pref
seq 10 permit 22.22.22.0/24
!
route-map SETWEIGHT permit 10
match ip address prefix-list 22pref
set weight 400
!
route-map SETWEIGHT permit 20
set weight 0
!
router bgp 1
router-id 1.1.1.1
neighbor 192.168.12.2 remote-as 2
neighbor 192.168.13.3 remote-as 2
neighbor 192.168.13.3 route-map SETWEIGHT in
!
end
Result
R1(config-route-map-SETWEIGHT)#show ip bgp
BGP routing table information for VRF default
Router identifier 1.1.1.1, 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
* > 2.2.2.0/24 192.168.12.2 0 100 0 2 i
* 2.2.2.0/24 192.168.13.3 0 100 0 2 i
* > 22.22.22.0/24 192.168.13.3 0 100 400 2 i
* 22.22.22.0/24 192.168.12.2 0 100 0 2 i