- Differentiate between Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP). …
- Differentiate between hard reset and soft reset in the context of BGP. …
- What do the various BGP Path Attributes mean? …
- What do you understand about communities in the context of BGP?
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Most Commonly Asked BGP Interview Questions
Frequently requested BGP questions, such as scenario-based BGP interview questions and BGP troubleshooting interview questions and answers, have been addressed in this blog.
BGP Interview Questions and Answers for Freshers
Border Gateway Protocol (BGP) is a protocol that allows two networks to communicate with one other. BGP is a standardized outside gateway protocol that allows autonomous systems (AS) on the Internet to share routing and reachability information. A route vector protocol is what the protocol is called. The Border Gateway Protocol is engaged in fundamental routing choices and determines routing decisions depending on pathways, network regulations, or rule sets a network administrator provides.
Within an autonomous system, BGP may be utilized for routing. Interior Border Gateway Protocol, often known as Internal BGP or iBGP, is used in this application. The protocols Internet implementation, on the other hand, is known as Exterior Border Gateway Protocol, External BGP, or eBGP.
CCIE Interview Questions for Preparations –
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What is the difference between the hard reset and soft reset in BGP? In case of hard reset the local router brings down the neighborship, brings down the underlying TCP connection and all the BGP table entries learned from that neighbor are removed. #clear ip bgp * command is used for hard reset. In case of a soft reset, the router does not bring down the BGP neighborship or the underlying TCP connection. However, the local router resends outgoing Updates and reprocesses incoming Updates adjusting the BGP table based on the current configuration. #clear ip bgp * soft command is used for soft reset.
Explain Loop prevention mechanism in BGP? BGP uses two mechanisms to prevent loops:- 1. When a router learns routes from an iBGP peer, that router does not advertise the same routes to another iBGP peer. 2. By using AS_PATH – When advertising to an eBGP peer, a BGP router adds its own ASN to the AS_PATH. If a BGP router receives an update and the route advertisement lists an AS_PATH with its own ASN, the router ignores that route. Note – A BGP router does not add its ASN when advertising to an iBGP peer.
Explain BGP Local preference? Local preference is an indication to the AS about which path has a preference to exit the AS in order to reach a certain network. A path with a higher local preference is preferred more. By default value for local preference is 100 and can be changed manually. Unlike the weight attribute, which is only relevant to the local router, local preference attribute is communicated throughout a single AS for the purpose of influencing the choice of best path to exit the AS.
What is Recursive Lookup? The router looks up the BGP route and the next hop to reach a destination in the remote AS. Then the router looks up the route to reach the next hop. In this way router has to perform lookup twice to reach to a destination, this process is called recursive lookup.
What is route reflector and why it is required? In BGP, route learned from an iBGP neighbor will not be advertised to another iBGP neighbor. To overcome this situation route reflector is used. It acts as a route reflector server and makes IBGP neighbors as route reflector clients enabling route advertisements between them.
FAQ
What is BGP protocol interview questions and answers?
- Weight.
- Local Preference (highest local value will be preferred, the default value is 100)
- Originate.
- AS path length.
- Origin code.
- Multi-Exit Discriminator (MED)
- eBGP path over iBGP path.
- Shortest IGP path to BGP next-hop.
Why BGP is preferred over OSPF?
Is BGP TCP or UDP?
Why does BGP use TCP port 179?
