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  1. Hi Rene,
    First of all- thank you for your amazing job !!!
    I just started working for a service provider and I am trying to figure out how MPLS VPN's work, I have a problem understanding a (probably basic for you) concept :
    - Is the VPN label created based on the Route Targets or on VRF's ? -I mean -if the customer wants to have some routes to be kept within their network and some to be shared with other customers, then he would use the same Route Distinguisher but different Route Targets ? - is that correct?
    Wouldn't you have to have something like 'VPN label to Route Target' table on the router ?
    Thank you

  2. Marek,
    This topic can become less confusing if you think about what is going on in the control plane vs the data plane. The RTs are used in the control plane to associate ROUTES with VRFs. The VPN label is used in the data plane to associate PACKETS with VRFs.

    Check out this great article that talks about why RDs, RTs, and VPN Labels are all needed:
    https://mellowd.co.uk/ccie/?p=2923

  3. Andrew- thank you, it all makes sense now!
    The link you shared is also awesome but it melted my brain until I realised the guy forgot to mention that R6 and R7 BOTH advertise route 6.6.6.6 :wink:

  4. Dear Rene,,
    I have encountered following log message when setting this up. Can you confirm if we need to make the Loopback Interfaces as /32 s across the MPLS core ?

    *Jan 15 01:49:04.853: %BGP-4-VPNV4NH_MASK: Nexthop 1.1.1.1 may not be reachable from neigbor 2.2.2.2 - not /32 mask

  5. This error occurs if you have a loopback interface with a subnet mask that is not /32 and that is advertised in OSPF.

    OSPF will always advertise a loopback as a /32 (network type LOOPBACK). LDP however, looks at the actual subnet mask of the interface so there will be a mismatch between LDP and your routing table.

    To fix this, you have two options:

    • Change the network type of your loopback interface to ip ospf network-point-to-point so that OSPF advertises the actual subnet mask of the interface.

    OR

    • Change the subnet mask of the loopback interface to /32.

    Rene

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