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New Member

LDP

hi all,

i failed the MPLS Exam with score 780

the passing score was 790

one of the questions that i think i didn't answer correctly is

which two of the following regarding LDP is true:

A. LDP can also be used between nonadjacent routers using multicast LDP Hello messages.

B. LDP doesnt require periodic hello message once the hLDP session has been establishment between the LDP peers.

C. LDP hello messages use TCP Packets with a destenation port of number of 646.

D. Multiple sessions can be establishment between a pair of LSRs if they use multiple label spaces.

E. Per-platform label space can be identified by label space ID of 0 in the LDP identifier field.

what do u think the correct choices ?

please advice?

4 REPLIES
New Member

Re: LDP

Well, I'm not an expert, but it a good exercise for me, as I am currently working for the MPLS exam.

A : wrong -> LDP nonadjacent sessions require a unicat transmission (refer to LDP RFC (3036), chap 2.4.2)

B : wrong -> To maintain the adjaceny, Hello messages are needed (refer to LDP RFC (3036), chap 2.5.5)

C : wrong -> Hello messages are built on UDP. TCP is used for Session messages (refer to LDP RFC (3036), chap 1.2)

D : true -> A single label space = an LDP session. If the LSR is for example an ATM switch, it manages a per interface label space. So if the pair of LSRs are connected by more than one link, multiple sessions are going to be established (refer to LDP RFC (3036), chap 2.2.3)

E : Well, by elimination I'd say true, but I'm not really sure. An LDP identifier contains 6 bytes. the 4st are dedicated to the LSR identifier and the 2 last one are dedicated to the label space. If the router is a per plateform labe space, it should be set to the 0. Therefore, if it's possible to set the LSR id to 0, the answer is definitly true.

An expert should confirm that answer

(refer to LDP RFC (3036), chap 2.2.2)

New Member

Re: LDP

Gauthier,

Great Answer. I like how you listed the RFC and the Chapter and Section. My organization is currently implementing an MPLS Network (managed by Verizon Business). I desire to learn MPLS so I can better understand the challenges that my organization will face in the future, but I am quite a degree away from being able to pursue CCIP.

It is good to know that the MPLS exam is the most difficult of the CCIP, and I will keep that in mind. I planned to pursue CCNP, then move on to CCIP. In what order should I educate myself for the CCIP by exam number?

What resources did you use to prepare for your MPLS Exam? You sound like you have really done your homework. I have the MPLS Definitive Guide, by Cisco Press (2005). What other resources would you recommend? Thank you for your assistance.

Regards,

John

New Member

Re: LDP

Hi,

I am CCIP myself and can tell you that the routing is a good starting point, then QoS (it is fairly easy), then BGP and finish with MPLS. this is important as MPLS relies on BGP (MP.BGP to be accurate).

A little trick for the MPLS/BGP exam : remember that whenever you change something to your BGP config, you have to reset your BGP links (a good old 'clea ip bgp *') otherwise, you are going to wonder, like me(!), why this thing does not work!

But the BGP is clearly easier than the MPLS. I used 2 books for the MPLS : the "MPLS VPN architecture vol.1" and the same as yours! As for the BGP, the Cisco Press book for CCIE ( BGP configuration handbook" is magic!

Go for it! It feels good when you're done!

New Member

Re: LDP

Hi,

MPLS is the toughest of the CCIP serie! The BGP is nothing compared to it!

D is right at least

C is wrong for sure

Don't remember the other ones...you will find the answers on this site!

I would say : D and E.

Good luck next time!

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