BGP INTERVIEW QUESTIONS

  1.     Explain Split-Horizon, Synchronization rules.
  2.     Which 2 new attributes are seen when we enable summarization in BGP?
  3.     Why BGP specifically chooses neighbor method for creating sessions and why not the sessions are allowed to be configured dynamically as happen in IGPs(say EIGRP and OSPF).
  4.     Two peers for iBGP neighborship on Loopback addresses while one of the peers doesn’t has update-source loopback x command missing. Explain why?
  5.     Can we form eBGP neighborship b/w two peers where one peer take physical interface address of remote-peer and 2nd peer taking loopback address of remote-peer. Yes or No, with explanation.
  6.     Explain BGP TTL Security concept with an example.
  7.     What is use of neighbor x.x.x.x local-as y command?
  8.     How can you prevent your BGP AS becoming a Transit-AS. Explain various methods.
  9.     Under one of Route-Reflector rules, a route advertised from a non client is not advertised to another non-client. Explain why.
  10.     When is command “remove private-as” in BGP used.
  11.     What are terms route-servers and looking-glass?
  12.     What 2 new attributes are seen when we configure a route-reflector in the topology.
  13.     Explain route-refresh capability in BGP and its use.
  14.     What is difference b/w the output of commands “show ip bgp neighbor x.x.x.x routes” and “show ip bgp neighbor x.x.x.x received-routes”.
  15.     A bgp peer’s neighborship getting reset every 3 mins(or say on hold time expiry). Explain the reason and the solution.
  16.     Explain the difference b/w standard communities “no-export”, and “local-as”.
  17.     The router advertises a prefix to its peer even when it is marked with the community “no-advertise” using command neighbor x.x.x.x route-map COMM out. Explain why?
  18.     Name few BGP process names seen in  “show process cpu”.
  19.     What are the 3 well-known mandatory attributes?
  20.     Explain the meaning of "next-hop-self"keyword and when it is used in BGP?
  21.     Explain BGP MRAI timer. What are its default values?
  22.     What is default Weight of remote prefix on a router?
  23.     Can we set local-preference in an outward direction to a peer? if yes, how?
  24.     What is use of “as-set” keyword in BGP route aggregation.
  25.     Explain the meaning for “rib-failure”? Where and when is this seen?
  26.     A route is present in the BGP table but not getting exported to routing table. Explain the possible reasons.
  27.     Explain various methods of load balancing in BGP.
  28.     Explain BGP Backdoor concept.
  29.     What is default metric when a RIP, EIGRP, OSPF, or an ISIS route is redistributed into BGP?
  30.     What transport protocol is used for BGP?
  31.     What is the origin-as for a prefix with the AS-Path 200 500 100 450?
  32.     Can we configure “update-source loopback x” command with eBGP peers?
  33.     Why we have to use ebgp-multihop x command for non directly connected eBGP peers?
  34.     How can we generate a label for a prefix using BGP?
  35.     Say on Router R1, there is a BGP configuration  “neighbor x.x.x.x route-map XYZ out”, and the route-map “XYZ” doesn’t exist. Will router R1 be able to communicate/send updates to peer x.x.x.x?
  36.     Under the above scenerio again, now say that we have the route-map “XYZ” but there are no rules under it and it is an empty route-map. Will router R1 be able to communicate/send updates to peer x.x.x.x now ? What is the solution to above two problems?
  37.     How would you match an existing community attribute say “100:100” on a BGP router and add an additional BGP community 200:200 to it?
  38.     One of the route-reflector rules say that a  route learned by an RR from a non client is not advertised to another non clients but only to its clients. Explain why?
  39.     What are BGP “attribute-map” and “suppress-map” terms? When are these used?
  40.     Explain the attribute “Aggregate-address”. What is its function?
  41.     What is use of “as-set” keyword in BGP route-aggregation?
  42.     You have set a community “no-advertise” for a prefix in out direction to a peer. The prefix is still advertised to the peer. Why? How can you solve this?
  43.     What are as-path access-lists? When are these used?
  44.     What is BGP route-dampening?
  45.     We are able to ping the BGP peer but not able to establish BGP session. What are the possible reasons?
  46.     Can you form an eBGP session b/w two peers, where peer A is using peer B’s loopback address to create session and peer B is using peer A’s physical interface address?
  47.     Can BGP generate labels? Explain how?
  48.     What are BGP peer-groups? What is its use?
  49.     Explain BGP states.
  50.     Explain the fields of BGP “OPEN” message?
  51.     Do BGP messages have any header? What is minimum length of the header?