This is first lab in a new Boarder Gateway Protocol (BGP) series that I will be posting over the next few months. In this lab we will start with some very basic BGP configuration. If you are new to BGP you need to know that each BGP router belongs only to one Autonomous System (AS), and BGP neighbors can be of two types: 

•Internal Border Gateway Protocol (IBGP) neighbors – when two neighbors are in the same AS;

• External Border Gateway Protocol (EBGP) neighbors – when two neighbors belong to different AS.

In this article we’ll build a simple BGP scenario in GNS3 using four Cisco routers, which we will configure with both types of BGP neighbor relationships.

To configure BGP start by entering the Cisco IOS command router BGP followed by an AS number which enters you to BGP configuration mode.

Note that a router can belong only to a single BGP Autonomous System

Next, configure BGP neighbors with neighbor (IP-address | peer-group-name) remote-as AS command.

In this lab we will set neighbors based on the IP address not the peer groups. To tell to the router what to advertise use this command: network network-address [mask network-mask]. Wow you have just configured your router to be part of an BGP AS.

Learning Objectives:


  1. Configure the IP address and subnet mask for all FastEthernet  and Serial interfaces as shown in the network diagram.
  2. Configure the IP address and subnet mask for all loopback interfaces for R1 and R2 as shown in the network diagram.
  3. Configure BGP on R1 and BR1 as AS-65100.
  4. Configure BGP on R2 and BR2 as AS-65200.
  5. Configure neighbor relationships between R1 and BR1, R2 and RB2, and BR1 and BR2.
  6. Advertise loopback address for R1 and R2.

Tools to verify bgp status:

  • show ip bgp;
  • show ip bgp summary;
  • show ip bgp neighbors;
  • show ip bgp rib-failure.

Let’s examine these commands using the lab we just configured:

Download this lab now to see more:

  Basic BGP (181.2 KiB, 1,937 hits)

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