Does BGP use shortest path?

Does BGP use shortest path?

Reality: Internet routing using BGP does not follow the shortest path! The core protocol that governs how traffic is routed long distances across the Internet is called Border Gateway Protocol (BGP).

How does BGP decide best path?

If there are no specific settings that can affect the outcome, BGP Best Path Selection Algorithm determines the best route by selecting the shortest path to the destination. An Autonomous System is a single network or a set of networks and routers, which are under the control of one administrative entity.

How does BGP use the AS path attribute?

The BGP AS path is a well-known mandatory attribute, which means that it’s present for all prefixes exchanged between BGP neighbors. So the AS path lists all the ASes that need to be traversed to reach the location where the prefix that the path is attached to is advertised from.

WHAT IS AS path BGP?

An AS path is the autonomous systems that routing information passed through to get to a specified router. It indicates the origin of this route. 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.

Does BGP avoid congestion?

Like most other routing protocols, the BGP protocol does not detect congestion.

What is the most preferred attribute for BGP?

BGP Best Path Selection Algorithm

• A path with the highest Weight attribute is preferred (other vendors ignore this attribute).
• A path with the highest “local preference” is preferred (usually set to 100).

What is the best way to remember BGP path selection?

BGP Best Path Algorithm Mnemonic

1. Weight (Highest is better)
2. LOCAL_PREF (Highest is better)
3. Originated Locally.
4. AS_PATH (shortest)
5. ORIGIN Type (IGP is lower than EGP and EGP is lower than Incomplete)
6. MED (lowest is better)
7. Paths (External > Internal)
8. RID (Router ID – lowest is better)

How does BGP use the AS path attribute How does it use the next hop attribute?

The BGP nexthop attribute is the next hop IP address that is going to be used to reach a certain destination. For EBGP, the next hop is always the IP address of the neighbor specified in the neighbor command. For IBGP, the protocol states that the next hop advertised by EBGP should be carried into IBGP.

What is the advantage of using BGP AS prepend?

AS-PATH prepending changes the way that your advertised prefixes appear to the rest of the Internet. The as-path length is evaluated early on in the path select process so this is a powerful tool to use with BGP. The shorter the AS-PATH the more preferred a prefix becomes.

WHAT IS AS path length?

The Border Gateway Protocol (BGP) provides a feature called AS path length. It represents the sequence of AS hops that a BGP route follows from a particular AS (the traffic sender) towards the origin AS (the traffic receiver). One of the common route selection rules in BGP is ‘shortest AS path’.

How does it use the AS path attribute?

In AS Path Attribute mechanism, whenever a route passes an AS (Autonomous System), it adds the number of AS it passed. So, AS Path Attribute is a list of AS numbers, that the router traverse. With this mechanism AS Path Attribute is also used for loop detection and loop avoidance.