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BGP Route Reflectors

Here you will find answers to BGP Route Reflectors Questions

Question 1

Which configuration task requires configuring the bgp cluster-id {cluster-id} command?

A. configuring the member ASs within a BGP confederation
B. configuring the BGP confederation ID
C. configuring hierarchical BGP confederations
D. configuring redundant BGP confederations
E. configuring hierarchical route reflectors
F. configuring redundant route reflectors

 

Answer: F

Question 2

Based on the R1 router BGP configuration shown, which three statements are correct? (Choose three)

hostname R1 ;
router bgp 50001
bgp confederation identifier 50101
bgp confederation peers 50002 50003
neighbor 10.1.1.1 remote-as 50001
neighbor 10.2.2.2 remote-as 50001
neighbor 10.3.3.3 remote-as 50001
neighbor 10.1.1.1 router reflector-client
neighbor 10.2.2.2 router reflector-client
neighbor 10.3.3.3 route-reflector-client
neighbor 10.4.4.4 remote-as 50002
neighbor 10.5.5.5 remote-as 50003
neighbor 192.168.100.1 remote-as 50102
neighbor 192.168.100.1 route-map setlp in
neighbor 192.168.100.1 route-map setmed out
no sync
!

A. R1 is in AS 50101 according to the 192.168.100.1 neighbor.
B. R1 is in AS 50101 according to the 10.1.1.1 neighbor.
C. The 192.168.100.1 neighbor must be directly connected to R1.
D. R1 is a route-reflector client.
E. The 10.4.4.4 neighbor is an EBGP neighbor.
F. BGP updates coming in from the 192.168.100.1 neighbor must be processed by the setlp route-map.

 

Answer: A C F

Question 3

Refer to the diagram. What should be changed within AS 50001 to improve the route reflector design?

improve_route_design.jpg

A. Add a physical link between R1 and R2.
B. Add a physical link between the clients (R3 and R4, and between R4 and R5).
C. Remove the iBGP session between the two redundant RRs (R1 and R2).
D. Add an iBGP session between each pair of clients (between R3 and R4, R4 and R5).
E. Make R4 the RR and R1 and R2 its clients. R3 and R5 should be a non-RR/non-client.

 

Answer: A

Question 4

Based on the network diagram shown in the exhibit, both R5 and R6 are clients of the R2 RR. When the 10.0.0.0/8 iBGP update from R3 is received by the R2 RR, which router(s) will R2 reflect the update to?

iBGP_Update.jpg

A. R1 only
B. R5 and R6
C. R5, R6 and R1
D. R4, R5 and R6
E. R4, R5, R6 and R1
F. to no other router

 

Answer: C

Question 5

Which show command can be used to display the originator ID and cluster-list?

A. show ip bgp
B. show ip bgp sum
C. show ip route bgp
D. show ip route {prefix}
E. show ip bgp {prefix}
F.show ip bgp neighbors {ip address}

 

Answer: E

Categories: BGP + MPLS 642-691 Exam Tags:
  1. SC
    April 24th, 2011 at 13:56 | #1

    can any1 explain Q3.
    why by add a physical link between and R2 will improve something?
    thanks.

  2. Anon
    May 2nd, 2011 at 06:21 | #2

    @SC with regards to Q3

    As far as I can tell, none of those answers given will solve the problem. Adding in a physical link should not do a thing since we are inside an AS and we can assume full IP connectivity between all BGP Speakers.

    I am trying to trace how any BPG update will travel through this AS…

    If we receive a BPG update from the LEFT, R1 will receive it, and distribute it to all it’s iBPG peers (R2, R3 & R4). R2 will then reflect it to it’s RR Clients (R4 & R5). This will work with the only problem being R4 will receive the update twice (not a big deal, but not ideal)

    If we receive a BGP update from the RIGHT, R5 will receive it, and distribute it to all it’s iBGP peers (R2 only). R2 will reflect this to it’s RR Clients (R4 and back to R5). The updates will stop there and R1 & R3 will never hear any updates coming from the eBGP session on the RIGHT.

  3. NB
    May 4th, 2011 at 10:12 | #3

    @Anon
    R2 will reflect update from R5 to R1 and R4.

  4. Anon
    May 5th, 2011 at 03:35 | #4

    @NB
    It’s hard to say if that would be the case. The diagram doesn’t imply that R2 will reflect updates to R1. The way I am understanding that diagram is, an (RR) will only reflect to a (Client), and an (RR) will not reflect to another (RR).

    Either way, that doesn’t make answer A any more correct.

  5. Anon
    May 6th, 2011 at 05:24 | #5

    @NB
    Sorry you are correct, I just read this:
    “If the route is received from a client peer, reflect to all nonclient peers and also to
    client peers.”
    So because R2 received an update from a client peer, it reflects this update to all other peers.

  6. inviz
    July 11th, 2011 at 12:09 | #6

    You are both over complicating the question….what would happen if physical connection between R1 and R4 was to fail ? it would break the topology and R3 would not be able to talk to R4 or R5, this is the reason to add the physical connection between the 2 RR’s. Redundant RR’s should always be physically connected

  7. Ntando
    July 15th, 2011 at 15:08 | #7

    looking for latest Q&A for 642-691

  8. A.elsakka
    October 30th, 2011 at 05:31 | #8

    Inviz is correct as if the link between R4 and R2 went down R1 and R2 session will go down which will cause R5 to be the only client for R2 so R5 will never get any update from R1, R3 or R4.

  9. Hoannq
    April 3rd, 2012 at 02:45 | #9

    can anyone explain question 2, why must we choose A,C ?

  10. Anonymous
    May 2nd, 2012 at 08:10 | #10

    @Hoannq

    A. R1 is in AS 50101 according to the 192.168.100.1 neighbor.

    > EBGP neighbors will not recognise/see confederation AS’es of their peers. They will only see the actual AS. 192.168.100.1 is a EBGP neighbor as the remote-as doesnt appear in the confederation peers list.

    bgp confederation identifier 50101. This tells us R1 is in AS 50101. Also, 50102 does not show up in the confederation peers list indicating its EBGP.

    C. The 192.168.100.1 neighbor must be directly connected to R1.

    > We can infer as theres no ebgp-multihop statement to indicate its non-directly connected.

  11. Shouka
    May 13th, 2012 at 23:27 | #11

    @ inviz,
    Thx man 🙂

  12. SMa
    July 18th, 2012 at 20:24 | #12

    Question 2:

    answer C & F is clear but I still don’t get how answer A is valid!

    A. R1 is in AS 50101 according to the 192.168.100.1 neighbor.

    Just from the first 4 config line we can establish that R1 is in AS 50101

    hostname R1 ;
    router bgp 50001
    bgp confederation identifier 50101 –> Indicate that the “mothership” AS is 50101
    bgp confederation peers 50002 50003 –> Indicate other “member-as” which are part
    of the “mothership” AS

    So if R1 has a “router bgp 50001” process and it has declare it is part of the confederation 50101, then we know that the “mothership” AS 50101 has 3 members-as which are 50001, 50002, 50003.

    As mentioned before the 192.168.100.1 neighbor connect to a remote-as 50102.
    This AS (50102) is not in the list of member-AS (50001,50002,50003) that is within the “mothership” AS 50101. This makes this link an eBGP connection. However I do not see HOW this neighbor help us determined that we are in AS 50101 (“mothership” AS ) ????

    What through me off in this question is the part that says “…according to the 192.168.100.1 neighbor”. As mentioned just above, this eBGP neighbor does not help me to prove that I am in AS 50101.

    Then answer B has a similar wording except it point to another neighbor.
    B. R1 is in AS 50101 according to the 10.1.1.1 neighbor.

    “neighbor 10.1.1.1 remote-as 50001 ”

    This neighbor point to the remote-as 50001. This AS is a “member-as” of the confederation (or “mothership” AS). This is also the same AS as the AS our bgp router is running under.
    This make this connection an iBGP connection to R1. Again not indicating really that R1 is part of AS 50001..

    When you have answer CF, elimitated DE and you are left with A or B has the last missing choice…. I don’t understand why the answer A with the part “…according to the 192.168.100.1 neighbor” help’s me determine that R1 is really in AS 50001 and that answer B with the part “according to the 10.1.1.1 neighbor” is wrong.

    If anyone can shed some light. Let me know.

    P.S.: Sorry for using the new term “mothership”-AS, but I though it was giving a clearer picture. 🙂

  13. Dinesh Kumar
    December 7th, 2012 at 02:09 | #13

    in CCNA there is tutorial available for each topic before taking the questions and answers. but here it was not available if its available better for us to recalling… Since CCNA explanation given was very simple to learn by anyone.. same expecting for each topic in CCNP as well as CCI………..

  14. Amr Selim
    July 14th, 2014 at 02:41 | #14

    Dear SC
    Cisco recommended that the RR should to be fully meshed
    and each RR participate as a client to another RR to know about it’s networks
    in this question R1 know about R5 and R2 know about R3

  15. Archana Nair
    March 12th, 2015 at 06:21 | #15

    Very well presented post, i think this diagrams has added more value to the post. Good sharing.
    http://www.nettechindia.com/networking/certifications/MPLS-&-BGP.php

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