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Thursday, November 10, 2011 is the second session of Implement IPv4 in the CCIE R&S Lab Fundamentals and Written Bootcamp. In this critical session, we examine BGP in great detail, among other topics! Students are presented with lab configuration and written exam challenges. Here is a sample written exam challenge from this exciting course for our blog readers.
4. Which statements below regarding BGP are true? Choose three.
a. BGP uses TCP (port 169) in its operation
b. In order to view the “topology table” for BGP, use show ip bgp
c. The LOCAL_PREF attribute is optional in BGP updates
d. If a prefix was learned via redistribution, it possesses the IGP ORIGIN code
e. If an advertising router and a receiving router are internal peers and the NLRI of the update refers to a destination in a different AS, the NEXT_HOP is the IP address of the external peer from which the route was learned
f. If an advertising router and a receiving router are internal peers and the NLRI of the update refers to a destination in a different AS, the NEXT_HOP is the IP address of the internal peer from which the route was learned
NOTE: Be sure to post your thoughts in the comments area below! An official solution will follow the original post after several days in the comments area.
Anthony Sequeira CCIE, CCSI
Twitter: @compsolv
Facebook: http://www.facebook.com/compsolv
Tags: CCIE, CCIE BootCamp, CCIE R&S, CCIE R&S Training, CCIE Training
A, B , E
B,D and E
B – i would not say TOPOLOGY table, but its something like that
C – optional, for sure
E – correct, IBGP peers wont change the next hop
a,c,e
A> 179 port
B> RIB if two or more path is going to that destination then bgp choose only one path which is best is upload to the IP Routing table
C> i am little bit confiuse because The LOCAL_PREF attribute always in in BGP updates
D>when any prefix learned via redistribution, it possesses the INCOMPLTE ORIGIN code
E>it correct
F>worng
thks
right answers as I think
b
c
e
wrong
a = the right port is tcp 179
d =IGP origin is for local networks. With redistribution , it is marked as incomplete
F = IBGP peers wont change the next hop
Come on guys, it’s painful to read what answers you gave. Anthony is a very good trainer and deserve a much better readers than some who don’t know what TCP port BGP is using.
So…
A. BGP uses TCP port 179 (so A is False)
B. The “topology table” for BGP is calling …topology table or BGP Routing Information Base (RIB) and you can see it with “show ip bgp” (So B is True)
C. The LOCAL_PREF is Well-Known Discretionary attribute so may or may not be included in BGP Update messages (So C is True)
D. If a prefix was learned via redistribution, it possesses the incomplete ORIGIN code (So D is False)
E. If an advertising router and a receiving router are internal peers and the NLRI of the update refers to a destination in a different AS, the NEXT_HOP is the IP address of the external peer from which the route was learned (It’s the behavior of the NEXT_HOP when the update is received from a eBGP. So E is True and F is False)
a. BGP uses TCP (port 169) in its operation – False Port 179
b. In order to view the “topology table” for BGP, use show ip bgp – YES
c. The LOCAL_PREF attribute is optional in BGP updates – YES
d. If a prefix was learned via redistribution, it possesses the IGP ORIGIN code – False, it has ? as origin code
e. If an advertising router and a receiving router are internal peers and the NLRI of the update refers to a destination in a different AS, the NEXT_HOP is the IP address of the external peer from which the route was learned – Yes, that why need to use Next hop self command to avoid this situation
f. If an advertising router and a receiving router are internal peers and the NLRI of the update refers to a destination in a different AS, the NEXT_HOP is the IP address of the internal peer from which the route was learned
B C E