BGP Configuration

OcNOS-SP : Layer 3 Guide : VRF Lite Configuration Guide : BGP Configuration

BGP Configuration

Overview

Border Gateway Protocol (BGP) makes core routing decisions on the Internet using a table of IP networks or “prefixes” which designate network reachability among autonomous systems (AS). BGP is a path vector protocol or a variant of a distance-vector routing protocol. BGP does not involve traditional Interior Gateway Protocol (IGP) metrics, but routing decisions are made based on path, network policies, and/or rule sets. For this reason, it is more appropriately termed a reachability protocol rather than routing protocol.

Note: Enabling dynamic capability on the specific BGP peer will prevent BGP session to reset.

Topology

BGP topology for VRF

Configuration

#con t	Enter configuration mode.
(config)#ip vrf vrf1	Create vrf1
(config-vrf)#rd 800:1	Specify the route distinguisher in the VRF
(config-vrf)#route-target import 800:1	Specify the import route target
(config-vrf)#route-target export 800:1	Specify the export route target
(config-vrf)#exit	Exit VRF mode
(config)#router bgp 200	Enter the bgp configuration mode
(config-router)#address-family ipv4 vrf vrf1	Enter address family mode for vrf1
(config-router-af)#neighbor 2.2.2.2 remote-as 100	Specify the BGP neighbor and remote-AS.
(counter-router-af)#neighbor 2.2.2.2 activate	Activate neighbor in the address family
(config-router-af)#exit	Exit address family mode.
(config-router)#ex	Exit router mode
(config)#interface eth1	Enter interface mode
(config-if)#ip vrf forwarding vrf1	Associate the interface to vrf1
(config-if)#ip address 2.2.2.1/24	Configure the IP address 2.2.2.1 to eth1
(config-if)#commit	Commit the candidate configuration to the running configuration
(config-if)#exit	Exit interface mode

#configure terminal	Enter configure mode.
(config)#ip vrf vrf1	Create vrf1
(config-vrf)#rd 800:1	Specify the route distinguisher in the VRF
(config-vrf)#route-target import 800:1	Specify the import route target
(config-vrf)#route-target export 800:1	Specify the export route target
(config-vrf)#exit	Exit vrf mode
(config)#router bgp 100	Enter router mode.
(config-router)#address-family ipv4 vrf vrf1	Enter address family mode for vrf1
(config-router-af)#neighbor 2.2.2.1 remote-as 200	Specify the BGP neighbor and remote-as.
(counter-router-af)# neighbor 2.2.2.1 activate activate neighbor	Specify the BGP neighbor and remote-AS.
(config-router-af)#exit	Exit address family mode.
(config-router)#ex	Exit router mode
(config)#interface eth1	Enter interface mode
(config-if)#ip vrf forwarding vrf1	Associate the interface to vrf1
(config-if)#ip address 2.2.2.2/24	Configure the IP address 2.2.2.1 to eth1
(config-if)#commit	Commit the candidate configuration to the running configuration
(config-if)#exit	Exit interface mode

Validation

Verify the routing table in R1:

R1#show ip bgp neighbors

BGP neighbor is 2.2.2.2, vrf vrf1, remote AS 100, local AS 200, external link

BGP version 4, local router ID 2.2.2.1, remote router ID 2.2.2.2

BGP state = Established, up for 00:00:07

Last read 00:00:07, hold time is 90, keepalive interval is 30 seconds

Neighbor capabilities:

Route refresh: advertised and received (old and new)

Received 4 messages, 1 notifications, 0 in queue

Sent 5 messages, 0 notifications, 0 in queue

Route refresh request: received 0, sent 0

Minimum time between advertisement runs is 30 seconds

Connections established 2; dropped 1

Local host: 2.2.2.1, Local port: 49722

Foreign host: 2.2.2.2, Foreign port: 179

Nexthop: 2.2.2.1

Nexthop global: ::

Nexthop local: ::

BGP connection: non shared network

Last Reset: 00:00:12, due to BGP Notification received

Notification Error Message: (Cease/Other Configuration Change.)

Verify the routing table in R2:

R2#show ip bgp neighbors

BGP neighbor is 2.2.2.1, vrf vrf1, remote AS 200, local AS 100, external link

BGP version 4, local router ID 2.2.2.2, remote router ID 2.2.2.1

BGP state = Established, up for 00:02:36

Last read 00:00:08, hold time is 90, keepalive interval is 30 seconds

Neighbor capabilities:

Route refresh: advertised and received (old and new)

Received 10 messages, 0 notifications, 0 in queue

Sent 9 messages, 1 notifications, 0 in queue

Route refresh request: received 0, sent 0

Minimum time between advertisement runs is 30 seconds

Connections established 2; dropped 1

Local host: 2.2.2.2, Local port: 179

Foreign host: 2.2.2.1, Foreign port: 49722

Nexthop: 2.2.2.2

Nexthop global: ::

Nexthop local: ::

BGP connection: non shared network

Last Reset: 00:02:41, due to Configuration Change (Cease Notification sent)

Notification Error Message: (Cease/Other Configuration Change.)

R1#show ip route vrf vrf1

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 "vrf1"

C 2.2.2.0/24 is directly connected, eth1, 00:04:03

Gateway of last resort is not set

R2#show ip route vrf vrf1