Top BGP Interview Questions (2024)
What is BGP?
What is the difference between eBGP and iBGP?
What is the significance of BGP attributes?
What is an AS (Autonomous System)?
What is the AS Path attribute?
What is the Local Preference attribute?
What is the purpose of the Next Hop attribute?
What is the MED (Multi-Exit Discriminator) attribute?
What is a BGP Community attribute?
What is BGP route reflector?
How does BGP handle route flapping?
What is the BGP Confederation?
How does BGP select the best path?
What is BGP synchronization?
How do you troubleshoot BGP issues?
Q: What is BGP?
Ans:
An outer gateway protocol called BGP (Border Gateway Protocol) makes it easier for different Internet autonomous systems (AS) to exchange routing data. It makes it possible for routers in many ASes to communicate and choose the most effective path for traffic forwarding.
Q: What is the difference between eBGP and iBGP?
Ans:
To exchange routing data between routers in various autonomous systems, eBGP (External BGP) is utilised. Within the same autonomous system, routing information is exchanged via iBGP (Internal BGP).
Q: What is the significance of BGP attributes?
Ans:
BGP attributes offer more details about routes and assist in routing decisions. AS Path, Next Hop, Local Preference, MED (Multi-Exit Discriminator), and Community are a few important features.
Q: What is an AS (Autonomous System)?
Ans:
A set of networks and routers that are all under the same administrative control is known as an AS. Assigned with special identification codes known as AS numbers (ASN), ASes are recognized globally in BGP.
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Q: What is the AS Path attribute?
Ans:
A list of AS numbers that the route traversed through is given in the AS Path attribute. It enables routers to find the quickest path to a destination which helps in preventing routing loops.
Q: What is the Local Preference attribute?
Ans:
An autonomous system uses the Local Preference feature to specify the desired exit destination for outgoing traffic. The route with the greatest Local Preference value is selected as the preferred route by routers inside the AS.
Q: What is the purpose of the Next Hop attribute?
Ans:
The IP address of the next hop router towards the target network is specified by the Next Hop attribute. Routers utilise it to decide which router they should forward traffic to next.
Q: What is the MED (Multi-Exit Discriminator) attribute?
Ans:
When an AS has numerous entry points, the MED attribute is utilized to influence the routing decision of external routers. It is an indicator given from one AS to another regarding the recommended routing for incoming traffic.
Q: What is a BGP Community attribute?
Ans:
Routes with a particular community value are marked with the Community attribute. It enables more granular control over routing by allowing network operators to group routes and apply policies based on these communities.
Q: What is BGP route reflector?
Ans:
In order to satisfy the entire mesh requirement for iBGP peers, the BGP route reflector technique is required. By doing so, a full mesh topology is not necessary for a router to reflect BGP updates received from one iBGP peer to other iBGP peers.
Q: How does BGP handle route flapping?
Ans:
When a route continuously switches between being available and unavailable, this is known as BGP route flapping. Route flapping is suppressed by BGP using measures like route dampening, which reduces its impact on network stability.
Q: What is the BGP Confederation?
Ans:
BGP Confederation is a method for getting around BGP's scalability issues in big autonomous systems. It makes it possible to split up an AS into more manageable sub-ASes, which reduces the complexity of the routing infrastructure.
Q: How does BGP select the best path?
Ans:
BGP selects the best way from a variety of possible paths using a set of criteria known as the BGP path selection process. The parameters are the AS Path Length, Origin Type, Local Preference, MED, and the eBGP router with the shortest IGP path to the Next Hop.
Q: What is BGP synchronization?
Ans:
A feature known as BGP synchronization makes sure that BGP routers only advertise routes learned through BGP to other BGP routers when those routes are actually existent in the underlying IGP (Interior Gateway Protocol) routing table. It avoids routing loops.
Q: How do you troubleshoot BGP issues?
Ans:
Examining BGP routing tables and attributes, looking at BGP routing messages, analyzing BGP messages, and using tools like route reflector logs and BGP debug commands are all part of troubleshooting BGP problems.