My new BGP book: 'Internet Routing with BGP' by Iljitsch van Beijnum BGPexpert My BGP book from 2002: 'BGP' by Iljitsch van Beijnum

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BGP Questions

Note that I'm completely oblivious as to Cisco's certification program. Don't assume these questions are like those on a certification test.

  • Question 1

    What are IGPs and EGPs and why are they different?

  • Question 2

    What do BGP, eBGP, iBGP and AS stand for? What's the difference between eBGP and iBGP?

  • Question 3

    Name several path attributes and their function.

  • Question 4

    What is the global routing table? What is (roughly) its size?

  • Question 5

    Why is there a problem with iBGP in large networks? How can this problem be solved? Describe each solution in 1 - 3 sentences.

  • Question 6

    Unlike all other routing protocols, BGP uses TCP as its transport protocol. Discuss the consequences of running BGP over UDP. (What would happen and/or what would have to be changed in BGP.)

  • Question 7

    What are the disadvantages of existing and proposed BGP security mechanisms?

  • Question 8

    Suppose AS 10 is a multihomed customer of AS 20 and AS 30. AS 10 receives most of its incoming traffic over AS 30 and wants to employ traffic engineering techniques to shift some of this traffic from AS 30 to AS 20. For this purpose, a route map is created. Assume that the following excerpt of the BGP table is a good representation of the BGP table as a whole:

    Network Next Hop Metric LocPrf Weight Path *>i12.31.126.0/24 213.24.40.91 0 100 0 20 209 13606 i * 62.93.19.27 0 0 30 209 13606 i * i12.31.127.0/24 213.24.40.91 0 100 0 20 209 7018 23087 i *> 62.93.19.27 0 0 30 7018 23087 i * i12.31.159.0/24 213.24.40.91 0 100 0 20 209 7018 20457 i *> 62.93.19.27 0 0 30 4181 20457 i

    Questions:

    1. Which BGP attributes would AS 10 possibly like to change in the route map "set" clause, in what way (higher/lower, longer/shorter), and which would be the best choice?

    2. 8b. Should a "match" clause be used in this route map?

    3. Should the route map be applied to:

      The BGP session with AS 20 "in"
      The BGP session with AS 20 "out"
      The BGP session with AS 30 "in"
      The BGP session with AS 30 "out"

  • Question 9

    What is the function of the connection collision detection mechanism?

  • Question 10

    What is the "longest match first" rule and what does it do? (Provide an example if necessary.)

  • The answers