Quick Answer: How Does BGP Determine Best Path?

Is BGP Layer 3 or 4?

BGP is a Layer 4 protocol that sits on top of TCP.

It is much simpler than OSPF, because it doesn’t have to worry about the things TCP will handle.

Peers that have been manually configured to exchange routing information will form a TCP connection and begin speaking BGP..

What is BGP Prepending?

In the Border Gateway Protocol (BGP), prepending is a technique used to deprioritize a route by artificially increasing the length of the AS-PATH attribute by repeating an autonomous system number (ASN). Route selection in BGP prefers the shorter AS path length, assuming all other criteria are equal.

What is BGP AS path?

An AS path is the autonomous systems that routing information passed through to get to a specified router. … The AS path is used to prevent routing loops in BGP. You can use this routing information to prefer one path to a destination network over another.

What metric does BGP use?

Previous versions of BGP (v2 and v3) defined this attribute as the inter-AS metric (INTER_AS_METRIC) but in BGPv4 it is defined as the multi-exit discriminator (MULTI_EXIT_DISC). The MED is an unsigned 32bit integer. The MED value can be any from 0 to 4,294,967,295 (2^32-1) with a lower value being preferred.

How routers determine the best path?

A primary function of a router is to determine the best path to use to send packets. To determine the best path, the router searches its routing table for a network address that matches the destination IP address of the packet.