What is the Difference Between EBGP and IBGP?

EBGP (Exterior Border Gateway Protocol) and IBGP (Interior Border Gateway Protocol) are two variations of the Border Gateway Protocol (BGP) used for routing in autonomous systems (AS). The main differences between EBGP and IBGP are:

1. Connectivity: EBGP is used to connect networks between different autonomous systems, while IBGP is used to connect networks within the same autonomous system.
2. Full Mesh Requirement: EBGP does not require a full mesh of routers, while IBGP does.
3. ASPATH Attribute: EBGP uses an ASPATH attribute for loop prevention, whereas IBGP does not.
4. Update Delivery: EBGP sends updates over TCP port 179 and uses a hop-by-hop approach for path selection, while IBGP sends updates over TCP port 179 and uses a recursive approach for path selection.
5. Administrative Distance: EBGP has a default administrative distance of 20, while IBGP has a default administrative distance of 200.
6. Route Advertisement: EBGP routes received from an EBGP peer can be advertised to EBGP and IBGP peers, while IBGP routes received from an IBGP peer cannot be advertised to another IBGP peer but can be advertised to EBGP peers.
7. Usage: EBGP is used between organizations or between organizations and Internet Service Providers (ISPs), while IBGP is used within the same organization.
8. Loop Prevention: EBGP uses the AS_PATH attribute for loop prevention, while IBGP uses the BGP Split horizon for loop prevention.

Comparative Table: EBGP vs IBGP

Here is a table comparing the differences between EBGP (Exterior Border Gateway Protocol) and IBGP (Interior Border Gateway Protocol):

EBGP and IBGP are both essential components of the Border Gateway Protocol (BGP), which is responsible for exchanging routing information between autonomous systems on the internet. While EBGP is used for propagating routes between different autonomous systems, IBGP is used for propagating routes within the same autonomous system.