BGP series and here I would like to talk about basic bgp configuration. If you are new to bgp you need to know that each BGP router belong only to one Autonomous System (AS), and BGP neighbors can be of two types:
• IBGP neighbors – when two neighbors are in the same AS;
• EBGP neighbors – when two neighbors belong to different AS
IBGP means Internal BGP, and EBGP means External BGP. In this article we’ll build a simple BGP scenario in GNS3 on Cisco devices, where will configure both types of BGP neighbor relationships. See below the scenario I have prepared. IBGP means Internal BGP, and EBGP means External BGP. In this article we’ll build a simple BGP scenario in GNS3 on Cisco devices, where will configure both types of BGP neighbor relationships. See below the scenario I have prepared.
you can see that R1 with BORDER_1 and R2 with BORDER_2 are IBGP neighbors whileBORDER_1 with BORDER_2 are EBGP neighbors (because they belong to different AS).
You have few tools to verify bgp status:
• show ip bgp;
• show ip bgp summary;
• show ip bgp neighbors;
• show ip bgp rib-failure.
Configration
R1#config t
R1(config)#interface fa0/0
R1(config-if)#ip address 192.168.0.2 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#router bgp 64520
R1(config-router)#neighbor 192.168.0.1 remote-as 64520
BORDER_1
BORDER_1# config t
BORDER_1(config)#interface fastEthernet 0/0
BORDER_1(config-if)#ip address 10.0.0.1 255.255.255.0
BORDER_1(config-if)#no shutdown
BORDER_1(config-if)#interface fastethernet 0/1
BORDER_1(config-if)#ip address 192.168.0.1 255.255.255.0
BORDER_1(config-if)#no shutdown
BORDER_1(config)#router bgp 64520
BORDER_1(config-router)#neighbor 192.168.0.2 remote-as 64520
BORDER_1(config-router)#neighbor 10.0.0.2 remote-as 64530
BORDER_1(config-router)#network 192.168.0.0 mask 255.255.255.0
BORDER_2
BORDER_2(config)#interface fastEthernet 0/0
BORDER_2(config-if)#ip address 10.0.0.2 255.255.255.0
BORDER_2(config-if)#no shutdown
BORDER_2(config-if)#interface fa0/1
BORDER_2(config-if)#ip address 192.168.100.1 255.255.255.0
BORDER_2(config-if)#no shutdown
BORDER_2(config)#router bgp 64530
BORDER_2(config-router)#neighbor 10.0.0.1 remote-as 64520
BORDER_2(config-router)#neighbor 192.168.100.2 remote-as 64530
BORDER_2(config-router)#network 192.168.100.0 mask 255.255.255.0
R2
R2(config)#interface fastEthernet 0/0
R2(config-if)#ip address 192.168.100.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#router bgp 64530
R2(config-router)#neighbor 192.168.100.1 remote-as 64530