BGP Load Balancing on Multiple ISP Links

BGP Load Balancing

Question

A company is running BGP on a single router, which has two connections to the same ISP.

Which BGP feature ensures traffic is load balanced across the two links to the ISP?

Answers

Explanations

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A. B. C. D.

B.

The correct answer is B. Multipath Load Sharing.

BGP (Border Gateway Protocol) is an exterior gateway protocol (EGP) that is used to exchange routing information between different Autonomous Systems (AS). BGP can be used to connect to multiple ISPs for redundancy or load balancing purposes.

In this scenario, the company has two connections to the same ISP and is running BGP on a single router. The goal is to ensure that traffic is load balanced across the two links to the ISP.

One way to achieve this is to use the BGP Multipath Load Sharing feature. This feature allows BGP to install multiple paths to the same destination in the routing table and load balance traffic across them.

To enable BGP Multipath Load Sharing, the following conditions must be met:

  1. The paths must have the same weight and local preference values.
  2. The paths must be from different autonomous systems or have different next-hop addresses.
  3. The "maximum-paths" command must be configured in BGP.

Once the conditions are met, BGP will install multiple paths to the same destination in the routing table and load balance traffic across them.

Option A, Multihop, is used when a BGP peer is not directly connected and requires more than one hop to reach.

Option C, Next-Hop Address Tracking, is used to track the next-hop reachability in BGP and update the next-hop address accordingly.

Option D, AS-Path Prepending, is used to manipulate the AS path attribute of a BGP route to make it less attractive to other BGP peers.

Therefore, the correct answer is B. Multipath Load Sharing.