BGP routing protocol Tips and Tricks

A routing mechanism called BGP (Border Gateway Protocol) is used on the Internet to communicate routing data between routers in various autonomous systems (AS). BGP is a strong and dependable protocol, but there are a few frequent problems that might arise during implementation and operation.

Fig 1.1- BGP Topology

Several of the frequent problems with BGP include:

Route Flapping: When a BGP route alternates repeatedly between being advertised and retracted, it is said to be flapping. Instability in the network and poor routing choices may result from this.

Routing loops: BGP does not have a built-in loop prevention mechanism, so if there are errors in the routing configuration, a routing loop can occur, in which packets are forwarded indefinitely between routers. But we have two scenarios to avoid loops

• When a router finds its own AS number in the AS path attribute for EBGP, it will drop the BGP advertisement, according to the AS-Path attribute.
• One IBGP neighbor should not provide an update to another IBGP neighbor, according to the split horizon rule for IBGP.

Convergence time: BGP can take a considerable amount of time to converge and for all routers to become aware of changes in the network due to its lengthy convergence time.

Configuration errors: BGP is a complicated protocol that needs to be carefully configured to work as intended. Routing problems can be caused by configuration mistakes, such as inappropriate neighbor relationships or incorrect routing policies.

Lack of BGP filtering: The system may get too many routes and experience routing loops if BGP updates are not filtered.

Path Vector Limit: The path vector limit in BGP regulates the maximum number of AS that a route can pass through. The router won't accept a route if it goes over this restriction.

Conclusion
Implementing routing policies, correctly configuring and maintaining BGP routers, and having monitoring and troubleshooting tools available will all help to prevent or reduce these problems.

To further filter the routes that are propagated throughout the network, BGP communities, prefix-lists, and route-maps are advised.