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How to configure BGP between two different autonomous systems?

BGP short for Border Gateway Protocol is a translation protocols used to exchange routing information between different autonomous systems. BGP is true built-in policy based routing protocol and using TCP port 179 to update the BGP routing table. BGP basically designed to manage large scale networks or to configure multi-home environments and when redistribution is not possible between different protocols (between RIP, OSPF & EIGRP).

Today tip will help you configure BGP between two different types of routing protocols. In this case, we will try to configure three different routers with routing protocols OSPF & RIP and then complete the all routing tables using BGP.

Follow the network topology of three different class network in given figure:

Follow the network topology of three different class network in given figure:

Configuration to Enable OSPF & BGP on Router B

In global configuration Mode:

B (config) # router ospf 1

(Enable ospf protocol and 1 is Autonomous number)

B (config-router) # network 40.0.0.0 0.255.255.255 area 0

(Advertised router B Serial Network 40.0.0.0)

B (config-router) # network 210.100.20.0 0.0.0.255 area 0

(Advertised router B Ethernet Network 210.100.20.0)

B (config-router) #redistribute bgp 20 subnet metric 50

(Redistribute bgp into ospf)

Now configure BGP on router B

B(config)# router bgp 20

B (config-router) # neighbor 61.1.1.2 remote-as 10

B (config-router) #end

Now run show command to display the BGP updates.

B #show ip bgp

Now verify the routes in router B routing table, run the command

B #show ip route

Configuration to Enable RIP & BGP on Router C

In global configuration Mode:

C (config) # router rip

(Enable rip protocol)

C (config-router) # network 210.100.30.0

(Advertised router C Serial Network 210.100.30.0)

C(config)#ip route 40.0.0.0 255.0.0.0 61.1.1.1

(Create a static route to router A to complete routing table.)

Now configure BGP on router C

C(config)# router bgp 10

C (config-router) # neighbor 61.1.1.1 remote-as 20

C (config-router) #end

Now run show command to display the BGP updates.

C #show ip bgp

Now verify the routes in router C routing table, run the command

C #show ip route

Configuration to Enable OSPF & BGP on Router A

In global configuration Mode:

A (config) # router ospf 1

(Enable ospf protocol and 1 is Autonomous number)

A(config-router) # network 40.0.0.0 0.255.255.255 area 0

(Advertised router A Serial Network 40.0.0.0)

A(config-router) # network 210.100.10.0 0.0.0.255 area 0

(Advertised router A Ethernet Network 210.100.10.0)