mpls bgp forwarding

Hi

Could anyone explain difference between interface command 'mpls bgp forwarding' and 'mpls ip' when configuring an InterAS link?

interface Serial1/1:0
 ip address 192.168.13.1 255.255.255.0
 mpls ip or mpls bgp forwarding

Both commands seems to behave identically, except for mpls bgp forwarding not enabling LDP neighbour.

 

Jon

Comments

  • mpls ip - is required if you want to have labels assigned based on LDP/TDP setup.

    mpls bgp forwarding - this is designed for BGP assigned labels; this command appears on the interface after you put send-label command in BGP configuration

    More information about second option:

    http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fsiasleb.html#wp1044724

    Cheers,

    Seba

     

  • But why doesn't it appear on an interface in the non-S trains?
    Using normal 12.4 you can use the send-label as well, but you can't configure mpls bgp forwarding on the interface.






    Rick Mur
    CCIE #21946 (R&S)
    CCNP, CCIP, JNCIA-ER, MCSE





    On 9 jan 2009, at 04:02, Seba wrote:

    mpls ip - is required if you want to have labels assigned based on LDP/TDP setup.

    mpls bgp forwarding - this is designed for BGP assigned labels; this command appears on the interface after you put send-label command in BGP configuration

    More information about second option:

    http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fsiasleb.html#wp1044724

    Cheers,

    Seba

     



    Internetwork Expert - The Industry Leader in CCIE Preparation
    http://www.internetworkexpert.com

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  • seems a bit strange to me

    ASBR config:

    router bgp 12
     no bgp default ipv4-unicast
     no bgp default route-target filter
     bgp log-neighbor-changes
     neighbor iBGP peer-group
     neighbor iBGP remote-as 12
     neighbor iBGP update-source Loopback0
     neighbor 12.1.1.2 peer-group iBGP
     neighbor 192.168.13.3 remote-as 34
     !
     address-family ipv4
     neighbor iBGP activate
     neighbor iBGP next-hop-self
     neighbor 12.1.1.2 peer-group iBGP
     no auto-summary
     no synchronization
     exit-address-family
     !
     address-family vpnv4
     neighbor iBGP activate
     neighbor iBGP send-community extended
     neighbor 12.1.1.2 peer-group iBGP
     neighbor 192.168.13.3 activate
     neighbor 192.168.13.3 send-community extended

    interface Serial1/1:0
     ip address 192.168.13.1 255.255.255.0
     mpls bgp forwarding

    Does not need eBGP neigbour in address-family ipv4 - or send-label to do InterAS.

    Tested between 12.2S and 12.2SB routers

     

    Jon

  • I haven't tried it on 12.4, so I just don't know. I would say it is IOS feature...
    When you have configured label path using BGP what can you see in show mpls interface output? Is there any information about Label assignement enabled for BGP?

    Actually I was a bit mistaken about send-label requirement, and Jon included other scenario in his test output for InterAS config without send-label, where mpls bgp forwarding is inserted on the interface anyway.

    I will try to test it today.

    Cheers,

    Seba

    But why doesn't it appear on an interface in the non-S trains?
    Using normal 12.4 you can use the send-label as well, but you can't configure mpls bgp forwarding on the interface.




















    Rick Mur

    CCIE #21946 (R&S)

    CCNP, CCIP, JNCIA-ER, MCSE














    On 9 jan 2009, at 04:02, Seba wrote:


    mpls ip - is required if you want to have labels assigned based on LDP/TDP setup.

    mpls bgp forwarding - this is designed for BGP assigned labels; this command appears on the interface after you put send-label command in BGP configuration

    More information about second option:

    http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fsiasleb.html#wp1044724

    Cheers,

    Seba

     





    Internetwork Expert - The Industry Leader in CCIE Preparation
    http://www.internetworkexpert.com

    Subscription information may be found at:
    http://www.ieoc.com/forums/ForumSubscriptions.aspx




     

  • Explanation for your case (from command reference - http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fsiasleb.html#wp1066456):



    Usage Guidelines


    Us the mpls bgp forwarding
    command when you want to enable MPLS forwarding on directly connected
    loopback interfaces. This command is automatically generated by BGP for
    directly connected nonloopback neighbors.

    Cheers,

    Seba

    seems a bit strange to me

    ASBR config:

    router bgp 12
     no bgp default ipv4-unicast
     no bgp default route-target filter
     bgp log-neighbor-changes
     neighbor iBGP peer-group
     neighbor iBGP remote-as 12
     neighbor iBGP update-source Loopback0
     neighbor 12.1.1.2 peer-group iBGP
     neighbor 192.168.13.3 remote-as 34
     !
     address-family ipv4
     neighbor iBGP activate
     neighbor iBGP next-hop-self
     neighbor 12.1.1.2 peer-group iBGP
     no auto-summary
     no synchronization
     exit-address-family
     !
     address-family vpnv4
     neighbor iBGP activate
     neighbor iBGP send-community extended
     neighbor 12.1.1.2 peer-group iBGP
     neighbor 192.168.13.3 activate
     neighbor 192.168.13.3 send-community extended

    interface Serial1/1:0
     ip address 192.168.13.1 255.255.255.0
     mpls bgp forwarding

    Does not need eBGP neigbour in address-family ipv4 - or send-label to do InterAS.

    Tested between 12.2S and 12.2SB routers

     

    Jon

     

  • Actually I just found very nice document. Here is some extract:

    When using eBGP (IPv4 - by using the send-label command) or MP-eBGP
    (VPNv4) for label exchange over a non-MPLS enabled interface, “mpls bgp
    forwarding” is automatically configured under the interface.

    So I wasn't mistaken about send-label option, but my description wasn't good enough.

    URL - http://networkers-online.com/blog/?p=101

    Cheers,

    Seba

  • Thanks

    URL had very good descriptions and explanations on most InterAs scenarios. Uses this as complimentary to CCO.

    Testet it to be possible to enable InterAS between ASBRs in more ways:

    Link could have 'mpls ip' or 'mpls bgp forwarding' or both configured

    If you have 'mpls bgp forwarding' you may choose not to enable ipv4 send-label (for an VPNv4 connection)

     

    Jon

  • Dear All

    So far i can not understand what is the differnce between mpls bgp forwarding and mpls ip command

     

    i need further explaination when mpls bgp forwarding is sufficient and when mpls ip under an interface is a must. also LDP theoritically not doing label assigment for BGP routes, so can mpls bgp forwarding do this task with addition to sening labels ?!!

     

    Regards

    Tamer A.Saleh

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