Introduction to eBGP and iBGP

BGP is the Exterior Gateway Protocol used over Internet. In fact BGP is such a wonderful and flexible routing protocol that Service Provider private networks widely use BGP protocol to exchange networks. BGP can accommodate more than 600,000 IPv4 routes and can scale further. BGP does not advertise incremental updates or refresh network advertisements like IGPs.

BGP has been designed to function differently within own and between different AS. To support this behavior, BGP Neighborship can be formed in two types

1. iBGP (Internal Gateway Protocol) and
2. eBGP (External Gateway Protocol).

iBGP Neighbors

iBGP Neighbors are those who form neighborship within Same Autonomous System Number. Like in below example, R1 and R2 are 2 routers forming iBGP neighborship within same AS.

eBGP Neighbors

eBGP Neighbors are those who form neighborship between different Autonomous System Number. Like in below example, R1 and R2 are 2 routers forming eBGP neighborship within different AS.

Sample configuration: iBGP Neighborship

Below is example scenario of iBGP configuration between R1 and R2 –

R1

R2

Helpful iBGP verification commands –

 To check neighbor status

To verify TCP socket detail

To verify BGP running process

Sample configuration: eBGP Neighborship

Below is example scenario of eBGP configuration between R1 and R2 –

R1

R2

Helpful eBGP verification commands –

To check neighbor status

To verify Neighbor Detail information

To verify TCP socket detail

To verify BGP running process

Continue Reading:

eBGP vs iBGP: Know the difference between eBGP and iBGP

Troubleshooting directly connected eBGP neighbors

FAQs Related to eBGP & iBGP

What is the difference between IGP and iBGP?

• IBGP is a type of BGP, which is a routing protocol, and it is typically used when the two routers are members of the same Autonomous System (AS). Interior Gateway Protocol (IGP) is an umbrella term for a variety of routing protocols, such as EIGRP, OSPF, IS-IS, or RIP.

What is iBGP used for?

• Internal Border Gateway Protocol (IBGP) is used to facilitate communication between routers inside the same autonomous system. It ensures that all routers in the system have the same information about routes and enables them to create a full mesh topology, or to use a combination of route reflectors and confederation for learning about prefixes.

What is eBGP used for?

• Extended Border Gateway Protocol (EBGP) is an extension of the Border Gateway Protocol (BGP) which is used to facilitate communication between separate autonomous systems (AS). EBGP can be used to construct connections between autonomous systems which have been built with BGP, and it acts as the main protocol in establishing global Internet or AS connectivity.