BGP Multipath for IPv4
BGP supports multipath for IPv4 prefixes. BGP Multipath allows load-balancing traffic among multiple BGP routes. It supports both iBGP and eBGP routes. In case of eBGP, the routes should arrive from same AS number.
Topology
Figure 1-31: Multipath iBGP for IPv4
Configuration
Rtr1
#configure terminal | Enter the Configure mode. |
(config)#router bgp 100 | Assign the ASN value (100) to the BGP router. |
(config-router)#bgp router-id 2.2.2.2 | Configure a fixed Router ID (2.2.2.2). |
(config-router)#neighbor 30.30.30.9 remote-as 100 | Configure neighbor 30.30.30.9 for iBGP. |
(config-router)# address-family ipv4 unicast | .Under address family, Redistribute the static routes. |
(config-router-af)#redistribute static | Redistribute the static routes. |
config-router-af)# neighbor 30.30.30.9 activate | Activate the neighbor |
(config-router-af)#exit-address-family | Exit address-family mode. |
(config-router)#exit | Exit the BGP Router mode and return to the Configure mode. |
(config)#ip route 88.88.0.0/16 Null | Configure static route. |
(config)#commit | Commit the candidate configuration to the running configuration. |
Rtr3
#configure terminal | Enter the Configure mode. |
(config)#router bgp 100 | Assign the ASN value (100) to the BGP router. |
(config-router)#bgp router-id 4.4.4.4 | Configure a fixed Router ID (4.4.4.4). |
(config-router)#neighbor 40.40.40.9 remote-as 100 | Configure neighbor 40.40.40.9 for iBGP. |
(config-router)# address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
(config-router-af)#redistribute static | Redistribute the static routes. |
config-router-af)# neighbor 40.40.40.9 activate | Activate the neighbor |
(config-router-af)#exit-address-family | Exit address-family mode |
(config-router)#exit | Exit the BGP Router mode and return to the Configure mode. |
(config)#ip route 88.88.0.0/16 Null | Configure static route. |
(config)#commit | Commit the candidate configuration to the running configuration. |
Rtr4
#configure terminal | Enter the Configure mode. |
(config)#router bgp 100 | Assign the ASN value (100) to the BGP router. |
(config-router)#bgp router-id 6.6.6.6 | Configure a fixed Router ID (6.6.6.6). |
(config-router)#neighbor 50.50.50.9 remote-as 100 | Configure neighbor 50.50.50.9 for iBGP. |
(config-router)# address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
(config-router-af)#redistribute static | Redistribute the static routes. |
config-router-af)# neighbor 50.50.50.9 activate | Activate the neighbor |
(config-router-af)#exit-address-family | Exit address-family mode |
(config-router)#exit | Exit the BGP Router mode and return to the Configure mode. |
(config)#ip route 88.88.0.0/16 Null | Configure static route. |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
Rtr2
#configure terminal | Enter the Configure mode. |
(config)#router bgp 100 | Assign the ASN value (100) to the BGP router. |
(config)#bgp router-id 9.9.9.9 | Configure a fixed Router ID (9.9.9.9). |
(config-router)#neighbor 30.30.30.2 remote-as 100 | Configure neighbor 30.30.30.2 for iBGP. |
(config-router)#neighbor 40.40.40.4 remote-as 100 | Configure neighbor 40.40.40.4 for iBGP. |
(config-router)#neighbor 50.50.50.6 remote-as 100 | Configure neighbor 50.50.50.6 for iBGP. |
(config-router)#address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
config-router-af)# neighbor 30.30.30.2 activate | Activate the neighbor |
config-router-af)# neighbor 40.40.40.4 activate | Activate the neighbor |
config-router-af)# neighbor 50.50.50.6 activate | Activate the neighbor |
config-router-af)# max-paths ibgp 2 | Configure iBGP max-paths (2). |
(config-router-af)#exit-address-family | Exit address-family mode |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
Validation
#show ip bgp 88.88.0.0
BGP routing table entry for 88.88.0.0/16
Paths: (3 available, best #1, table Default-IP-Routing-Table) Not advertised to any peer
Local
30.30.30.2 from 30.30.30.2 (2.2.2.2)
Origin incomplete, metric 0, localpref 100, valid, internal, multipath- candidate, installed, best
Last update: Wed Mar 2 15:17:38 2016
Local
50.50.50.6 from 50.50.50.6 (6.6.6.6)
Origin incomplete, metric 0, localpref 100, valid, internal, multipath- candidate
Last update: Wed Mar 2 15:23:58 2016
Local
40.40.40.4 from 40.40.40.4 (4.4.4.4)
Origin incomplete, metric 0, localpref 100, valid, internal, multipath- candidate, installed
Last update: Wed Mar 2 15:21:45 2016
#show ip route
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
ia - IS-IS inter area, E - EVPN, v - vrf leaked
* - candidate default
IP Route Table for VRF "default"
C 30.30.30.0/24 is directly connected, eth1, 00:15:04 C 40.40.40.0/24 is directly connected, eth6, 00:14:30 C 50.50.50.0/24 is directly connected, eth3, 00:14:46 B 88.88.0.0/16 [200/0] via 40.40.40.4, eth6, 00:02:58
[200/0] via 30.30.30.2, eth1
C 127.0.0.0/8 is directly connected, lo, 00:19:21
C 192.168.52.0/24 is directly connected, eth0, 00:19:16 Gateway of last resort is not set
Gateway of last resort is not set
#show running-config router bgp
!
router bgp 100
bgp router-id 9.9.9.9
neighbor 30.30.30.2 remote-as 100
neighbor 40.40.40.4 remote-as 100
neighbor 50.50.50.6 remote-as 100
!
address-family ipv4 unicast
max-paths ibgp 2
neighbor 30.30.30.2 activate
neighbor 40.40.40.4 activate
neighbor 50.50.50.6 activate
exit-address-family
!
Last modified date: 10/16/2023