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MPLS don't push label to BGP route

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  • 1.  MPLS don't push label to BGP route

    Posted 06-25-2018 19:10
      |   view attached

    Hi All

     

    I set a mpls enviroment with some routers. Looks like MPLS/LDP is established normallly.

    But routes learning from iBGP are not pushed label.

     

    Please refer to the sample configuration as the attachment.

    Can give me some suggestion to troubleshoot it ?

     

    Thanks 

    Cloud

     


    #MPLS

    Attachment(s)

    rtf
    MPLS.rtf   2K 1 version


  • 2.  RE: MPLS don't push label to BGP route

    Posted 06-25-2018 19:17

    Are you running l3vpn (inet-vpn) or bgp LU?

     

    Can you show your bgp config?

     

    also, bgp assign labels to vpn routes when family "inet-vpn" is enabled. it doesn't assign the labels to internal routes

     

     

     

     



  • 3.  RE: MPLS don't push label to BGP route

    Posted 06-25-2018 22:42

    Hi Kingsman

     

    Yes, I am running L3 VPN.

     

    I think my problem is still on LDP on OSPF with FRR. It will cause adjaceny that can't push label , and indirect router will be fine.

    Although I try to enable remote LFA to solve it, but it made my router's proccess crashing.

    Now I need to figure out  another workaround.

     

    Best regards,

    Cloud  



  • 4.  RE: MPLS don't push label to BGP route

    Posted 06-25-2018 23:42

    Hello,

    If routerA and routerB are directly connected, then by default the transport (LDP) label is 3 (implicit null).

    If You want to see a label pushed, enable "protocols ldp explicit-null" - that would be label 0.

    HTH

    Thx

    Alex



  • 5.  RE: MPLS don't push label to BGP route

    Posted 06-26-2018 01:24

    Hi 

     

    Thanks for your relpy and I think  you got what I confused.

    So, let say that direct connected router will display label 3 only by default ?

     

    Thanks

    Cloud 



  • 6.  RE: MPLS don't push label to BGP route

    Posted 06-26-2018 01:54

    Hi Cloud, 

     

    the route which you are cheking is learned via BGP.

     

    BGP doesn't advertise lable for internal routes unless you use BGP -LU family.

     

    and yes, as Alex mentioned, Directly connected neighbor advertise (LDP) lable 3 (implicit nul) for local prefix ( loopback address) to each other 



  • 7.  RE: MPLS don't push label to BGP route

    Posted 06-26-2018 02:57

    Hello,


    @Cloud wrote:

     

    So, let say that direct connected router will display label 3 only by default ?

     

     


    No, it will not "display" label 3. This label has a special meaning, it is never present in the packet and JUNOS does not show this label as being imposed/pushed.

    By default, it will advertise via LDP:

    1/ the FEC for own lo0.0 IP address(es) only

    2/ the associated label 3 (implicit null") for the above

    If You are not sure what FEC means please see RFC 5036 section 2

    https://tools.ietf.org/html/rfc5036#page-8

    HTH

    Thx

    Alex



  • 8.  RE: MPLS don't push label to BGP route

    Posted 06-26-2018 19:15

    Hi All

     

    So, if two router is connecting directly, showing any bgp route from each other will not be shown label what push by LDP. 

    Only bgp routes learnning from indirect adjaceny will be shown label.

    Am I correct about this ?

     

    Thanks

    Cloud 



  • 9.  RE: MPLS don't push label to BGP route
    Best Answer

    Posted 06-27-2018 01:09

    Hello,

    You are correct - if

    1/ You don't enable "protocol ldp explicit-null" knob

    2/ don't use RSVP with "protocols mpls explicit-null" knob

    HTH

    Thx

    Alex



  • 10.  RE: MPLS don't push label to BGP route

     
    Posted 06-30-2018 10:57

    Hi Folks,

    Just thought of sharing this pointer on “How-To: Build a service provider network with a single Juniper Networks box--Part 1” to check control plane behavior in one box…

     

    http://forums.juniper.net/t5/Routing/How-To-Build-a-service-provider-network-with-a-single-Juniper/ta-p/302237