neighbor send-label ?

Topology :

  PE-1       ----- P (RR)   ------ PE-2    (mpls enable).

 

P:router bgp <>

      address-family ipv4  

           neighbor <PE-1> route-reflector-client

           neighbor <PE-1> send-label



           neighbor <PE-2> route-reflector-client

           neighbor <PE-2> send-label

 

What is the fucntion of neighbor <PE> send-label on P node for ?

 

I thought the label exchange automatically enabled when enable mpls on interface.

 

Comments

  • How are you enabling MPLS though?  mpls ip enables LDP, not BGP labels.  This is what send-label does.

     

    Brian McGahan, CCIE #8593 (R&S/SP/Security)

    [email protected]

     

    Internetwork Expert, Inc.

    http://www.INE.com

     

    From: [email protected] [mailto:[email protected]] On Behalf Of AndiS
    Sent: Saturday, March 17, 2012 4:07 PM
    To: Brian McGahan
    Subject: [CCIE R&S] neighbor send-label ?

     

    Topology :

      PE-1       ----- P (RR)   ------ PE-2    (mpls enable).

     

    P:router bgp <>

          address-family ipv4  

               neighbor <PE-1> route-reflector-client

               neighbor <PE-1> send-label

               neighbor <PE-2> route-reflector-client

               neighbor <PE-2> send-label

     

    What is the fucntion of neighbor <PE> send-label on P node for ?

     

    I thought the label exchange automatically enabled when enable mpls on interface.

     




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  • Brian

    I ussually enable mpls ip on interface to distribute label between PE on MPLS VPN configuration. 

    I'm not familiar with BGP labels. What is ussually used for ? MPLS VPN Inter-AS ?

    http://www.cisco.com/en/US/docs/ios/12_2t/12_2t13/feature/guide/ftiasl13.html#wp1037040

    simple example/config will be great. Thanks!

     

     

  • If you have MPLS LDP path from ingrees PE to egrees PE, Then You dont need send-labe

     

    Lets look How Sned Label Work's 


    How BGP Sends MPLS labels with routes

    When BGP {eBGP/iBGP} distributes a route, it can also distribute an MPLS label that is maaped to that route. The MPLS label mapping information for the route is carried in BGP update message that contains the information about the route. Is a next hop is not changed, the label is preserved.

    You can issue neighbor send-label command on both of BGP router, the router advertise each other that they can then send MPLS Label with the routes {using AFI/SAFI: 1/4 in Open message}. If the routers successfully negotiate their ability to send MPLS labels, the routers adds MPLS label to all outgoing BGP update

    Neighbor x.x.x.x Send-label: enables a BGP router to send MPLS label with BGP refix to a neighbor

    It’s Always a good Practice to filter a specific routes via a route-map so that only a desired prefix are injected into a BGP table and propagated using IPv4 + labels. Proper filtering is required so that only loopback of PE and RR are advertised with the MPLS label

    You can use a route-map to filter {control} the distribution of MPLS label between routers

    • For the router distributing routes with MPLS label, you can specify which routes are distributed with MPLS label
      • For Distributing routes, You can use set mpls-label with route-map
      • Set-mpls label, Enables a route to distributed with an MPLS label if the route matches

    • For the router receiving routes with  MPLS label, you can specify which routes are accepted with label and installed in BGP table
      • For receiving routes, you need to configure match mpls-label using a route-map
      • Match mpls-label: Ensures that only BGP routes  with Labels are redistributed into the IGP; these should be the only routes that are reachable across the ASBR-link for PE router-to-PE router connectivity



  • “If you have MPLS LDP path from ingrees PE to egrees PE, Then You dont need send-label” is true if the PEs are learning each other’s routes via IGP.  For Intra-AS MPLS L3VPN, you would normally have an LDP+IGP path, or possibly MPLS TE with RSVP.  For Inter-AS MPLS L3VPN, you normally would not run IGP between the different ASes.

     

    This is the design where you would need to use BGP to exchange the MPLS labels: http://www.cisco.com/en/US/docs/ios-xml/ios/mp_ias_and_csc/configuration/15-1mt/mp-vpn-connect-ipv4.html

     

     

    Brian McGahan, CCIE #8593 (R&S/SP/Security)

    [email protected]

     

    Internetwork Expert, Inc.

    http://www.INE.com

     

    From: [email protected] [mailto:[email protected]] On Behalf Of Prakash.K
    Sent: Sunday, March 18, 2012 6:15 AM
    To: Brian McGahan
    Subject: Re: [CCIE R&S] RE: neighbor send-label ?

     

    If you have MPLS LDP path from ingrees PE to egrees PE, Then You dont need send-labe

     

    Lets look How Sned Label Work's 

    How BGP Sends MPLS labels with routes

    When BGP {eBGP/iBGP} distributes a route, it can also distribute an MPLS label that is maaped to that route. The MPLS label mapping information for the route is carried in BGP update message that contains the information about the route. Is a next hop is not changed, the label is preserved.

    You can issue neighbor send-label command on both of BGP router, the router advertise each other that they can then send MPLS Label with the routes {using AFI/SAFI: 1/4 in Open message}. If the routers successfully negotiate their ability to send MPLS labels, the routers adds MPLS label to all outgoing BGP update

    Neighbor x.x.x.x Send-label: enables a BGP router to send MPLS label with BGP refix to a neighbor

    It’s Always a good Practice to filter a specific routes via a route-map so that only a desired prefix are injected into a BGP table and propagated using IPv4 + labels. Proper filtering is required so that only loopback of PE and RR are advertised with the MPLS label

    You can use a route-map to filter {control} the distribution of MPLS label between routers

    • For the router distributing routes with MPLS label, you can specify which routes are distributed with MPLS label
      • For Distributing routes, You can use set mpls-label with route-map
      • Set-mpls label, Enables a route to distributed with an MPLS label if the route matches
    • For the router receiving routes with  MPLS label, you can specify which routes are accepted with label and installed in BGP table
      • For receiving routes, you need to configure match mpls-label using a route-map
      • Match mpls-label: Ensures that only BGP routes  with Labels are redistributed into the IGP; these should be the only routes that are reachable across the ASBR-link for PE router-to-PE router connectivity




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