Orhan Ergun 24 Comments

MPLS Design Question – MPLS is one of the most commonly used encapsulation method today. Especially on Wide Area Networks of the Service Providers, Large Enterprises and some datacenters.

Service Providers sell MPLS services to customers for decades. When customers want to have Service Provider redundancy so two MPLS circuit from different Service Providers, Inter AS MPLS service is created between those providers.

Or customers have a location where their MPLS service provider don’t have there but customer wants to have end to end MPLS connectivity between their all locations, again Inter MPLS Service is created between the providers.

If you are a visual learners and want to understand the basics of Inter AS MPLS VPN Options, check my youtube channel and subscribe for the more design videos.

For the below question, I expect familiarity with the MPLS and MPLS VPN operation.

Below picture depicts Inter AS MPLS VPN Option B architecture. Knowing and understanding the technologies and the protocols which are used in any architecture is important in real life network design as well as in CCDE certification exam.

What are the pieces to build ” end to end Inter AS MPLS VPN Option B architecture ” ?

Check the below options and share your answer in the comment box below, I will send a free webinar invite to all of the comment participants.

 

Inter

Figure – Inter AS MPLS VPN Option B

Question : Which technologies/protocols should be enabled on the PE1, P and PE3 in AS 100 and RR in AS200 ?

Answer A –

PE1 : IGP, MPLS, VRF, EBGP VPNv4

P : IGP , MPLS , VRF

PE3: IGP , MPLS, IBGP VPNv4

RR: IGP, MPLS, IBGP VPNv4

 

Answer B –

PE1: IGP, MPLS, VRF, IBGP VPNv4

P: IGP , MPLS

PE3: IGP , MPLS, IBGP VPNv4

RR: IGP, MPLS, IBGP VPNv4

 

Answer C –

PE1: IGP, MPLS, VRF, IBGP VPNv4

P: IGP , MPLS

PE3: IGP , MPLS, IBGP VPNv4,EBGP VPNv4

RR: IGP, MPLS, IBGP VPNv4

 

Answer D –

PE1: IGP, MPLS, IBGP VPNv4

P: IGP , MPLS

PE3: IGP , MPLS,EBGP VPNv4

RR: IGP, MPLS, IBGP VPNv4

 
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  • John

    C

  • Grzegorz Wypych

    Answer is C, however instead MPLS i will suggest to replace it with LDP. MPLS is just overall encapsulation format, not protocol itself to provide labels. Ofcrouse LDP is not the only choice, RSVP and BGP can also do labeling but in this situation I assume that core is base on LDP+IGP

  • Bassel Kablawi

    Option C because:

    PE1: needs a routing protocol to connects with its neighbors in the domain so that it need IGP and the IGP used also to provide the reachability to the iBGP peers.
    The iBGP used to carry the VPN4 traffic which used for MPLS L3 and the MPLS laying on the BGP and for sure we need to enable the MPLS and as the PE1 connected the CE we need VRF to provide the customer with the service.

    P: uses the IGP to connect with the other routers in the domain and act as a core so it must run IGP with both routers PE1 and PE3
    The MPLS configured to enable the MPLS and to put router P in the MPLS cloud and for labeling reasons too.
    The BGP did not mentioned here I think it should run iBGP to work as route reflector.

    PE3: the use of IGP and iBGP and MPLS the same of PE1 but here we dont have to have a VRF because no customer connected with it
    The eBGP used to connect AS 100 with AS 200

    Regarding RR, do you mean Route Reflector ?
    If yes the use of IGP and iBGP and MPLS will be for the reasons mentioned in PE1 and PE2

    Please consider my answer is a correct one, I answered from my mobile while I was stuck in the traffic jam and it took a long time to write the above lines 😀

  • J N

    Option C

  • JC

    I’d say option C. PE3 needs to speak both ebgp (peering with AS200) and ibgp within the AS100. The P router doesn’t need BGP at all, only IGP and MPLS.

    The PE1 needs VRF to carry the traffic from VPN B coming from the CE, and the RR needs ibgp to reflect the routes inside the AS200

  • Kamal

    C is the answer for this question.

  • benjaminlong

    C

  • Sadath Puthiyaveettil

    C

  • Bilal Saleem

    C

  • johny

    C

  • Prabhat bhatti

    C

  • Alvaro

    For Option B it should clearly be answer C.

  • Ric

    C, Sir.

  • Jignesh

    See

  • mohialdeen

    The answer is: C

  • Adam

    Saying C feels conformist.

  • Harpreet

    Option C

  • Harpreet

    C is the answer

  • Ramesh

    Option C but should RR also have EBGP VPNV4 running?

    • Orhan Ergun

      Hi Ramesh, No. That’s in Inter AS Option C, and in that case between PE3 of ASBR it would be RFC3107 not EBGPVPNv4

  • Mohamed Samir

    C is the correct answer

  • Mujtaba Bashir

    Answer: C

  • Tarun

    C is the Correct Answer to this question.

  • chris

    The Answer is C, PE1 has to have all necessary tech to allow MPLS VPN, PE3 must have the necessary to allow MPLS VPN plus eBGP since it communicates with an external AS. But for RR I am wondering why MPLS needed, if it is not on data plane path, it may or may not have MPLS.