This lesson introduces Border Gateway Protocol (BGP), the role it plays in connecting networks, and the distinction between internal and external BGP.
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol used to exchange routing and reachability information among autonomous systems (ASes). An AS is a network or group of networks administered under a common routing policy and identified by an autonomous system number.
All flashcards
What is BGP?
A standardized path-vector routing protocol that exchanges reachability and path information among autonomous systems. Administrators can use routing policies to influence which routes are accepted and selected.
What is an autonomous system?
A network or collection of networks administered under a common routing policy and represented in BGP by an autonomous system number.
How do iBGP and eBGP differ?
iBGP exchanges BGP information between peers in the same AS; eBGP exchanges it between peers in different ASes.
Why is BGP called a path-vector protocol?
Because its route information can include the sequence of autonomous systems on the path to a destination, rather than only a destination or a simple distance.
What does CIDR contribute to BGP-4?
CIDR allows flexible prefix-based addressing and supports route aggregation, helping reduce the number of entries that need to be advertised and maintained.
Quiz questions
What is the purpose of the BGP OPEN message?Answer: It starts session negotiation and carries peer identifiers, parameters, and optional capabilities.
What information can a BGP UPDATE message carry?Answer: Route announcements, withdrawals, and path attributes.
What must be true for a BGP route's NEXT_HOP to be usable?Answer: The router must be able to resolve the next-hop address through an active route.
How does a BGP community affect a route?Answer: It tags the route so receiving networks can apply their own configured policies.
What is BGP hijacking?Answer: An accidental or malicious false route announcement that can redirect traffic.