CCIE SP inter-AS MPLS L3VPN

Hello friends,

I have a few questions regarding inter-AS MPLS L3VPN

1] Why we have to use IBGP with MPLS ( mpls ip under the interface) inside an AS and EBGP with the command sen-label between AS .Why cannot we use IBGP with the command send-label inside an AS ?

2] Why we have to declare on inter-AS MPLS L3VPN architecture loopbacks networks on the PE which is directly connected to the other AS . for example on the inter AS option C exercice we declare on each side the loopbacks of R5, R2, XR2 and R6.

the question is why we have to declare them on the router R1 and XR1 and not on the routers that originate the networks?

thanks

Bobby

 

Comments

  • Hi Bobby,

    The assumption is the two AS are different service providers (SPs)  and not sharing any IGP (and LDP). Technically, yes you can use iBGP and do send label b/n them.

    To your second question, these Loopback are part of IGP with an AS and have to be somehow known by the remote SP (via redistribute to BGP from IGP so that the ASBR can send that to remote ASBR via BGP). The remote side needs these loopbacks to form VPNv4 neighborhood.

    Hope I have understood your question and gave you correct response....

    This may also help:



    TF

    On Mon, Dec 22, 2014 at 11:50 AM, Bobby_sixkiller <[email protected]> wrote:

    Hello friends,

    I have a few questions regarding inter-AS MPLS L3VPN

    1] Why we have to use IBGP with MPLS ( mpls ip under the interface) inside an AS and EBGP with the command sen-label between AS .Why cannot we use IBGP with the command send-label inside an AS ?

    2] Why we have to declare on inter-AS MPLS L3VPN architecture loopbacks networks on the PE which is directly connected to the other AS . for example on the inter AS option C exercice we declare on each side the loopbacks of R5, R2, XR2 and R6.

    the question is why we have to declare them on the router R1 and XR1 and not on the routers that originate the networks?

    thanks

    Bobby

     




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  • HI tfeleke,

     

    thank you for you reply.

    I tried to use in, an inter-AS MPLS L3VPN architecture, IBGP + Label (send-label) without LDP and this didn't work.

    Maybe I should retry, but what I misunderstand is, why in all the exercices I did, they all implement inside the AS : IBGP + LABEL + LDP .

    If IBGP + LABEL should work why use LDP ?

     

  • Hi Bobby,

    Still talking about option C? If so, you have to AS (AS1 and AS2). The ASBRs directly connected need to exchange Label for each other and for the RRs and PEs within their AS. The label exchange can be either done via BGP and IGP mutual redistribution (with proper RPL or route-map to limit scope) OR they can do it via iBGP and send label within their AS. The label exchange is just to setup the LSP transport path so that the two SPs can form VPNv4 connection to their CEs (customers).

    If you have access to INE option c lecture (part 2), it has is covered very nice .

    Pls send me your failed config.



    Sincerely,
    TF

    Sent from my iPhone

    On Dec 23, 2014, at 10:55 AM, Bobby_sixkiller <[email protected]> wrote:

    HI tfeleke,

     

    thank you for you reply.

    I tried to use in, an inter-AS MPLS L3VPN architecture, IBGP + Label (send-label) without LDP and this didn't work.

    Maybe I should retry, but what I misunderstand is, why in all the exercices I did, they all implement inside the AS : IBGP + LABEL + LDP .

    If IBGP + LABEL should work why use LDP ?

     




    INE - The Industry Leader in CCIE Preparation

    http://www.INE.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx
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