Routing

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  • 1.  Why we need routing protocol in MPLS

    Posted 02-26-2015 00:03

    Hi I am new in MPLS. I read This week: Deploying MPLS but cannot understand what role the routing protocol in MPLS is playing.

     

    For example, RSVP MPLS

    We may need ISIS or OSPF, iBGP, RSVP and MPLS configured under protocol.

    I don't understand how the IGP work with MPLS.

     

    Can anyone explain it for me? Or you can leave a link here that I can learn from. Thanks!

     



  • 2.  RE: Why we need routing protocol in MPLS
    Best Answer

     
    Posted 02-26-2015 00:59

    Hi jackeygor,

     

    I think the below URL/Article may help you to understand the concept.

     

    http://networkengineering.stackexchange.com/questions/10297/do-mpls-lsrs-require-a-layer-3-ip-routing-protocol

     

    Thanks,

    Suraj

    Please Mark My Solution Accepted if it Helped, Kudos are Appreciated too



  • 3.  RE: Why we need routing protocol in MPLS

    Posted 02-26-2015 02:03

    Thanks!

    Let me know if I am wrong.

    PE router: LSP ingress router, route lookup base on destination address and assign MPLS label

    P router: LSP trasnsit router, label lookup and forward packet (swap label)

     

    If we need a route table for route lookup, we only need to configure either iBGP or OSPF. Why do we need both IBGP and OSPF(or ISIS)?



  • 4.  RE: Why we need routing protocol in MPLS

     
    Posted 02-26-2015 03:18

    Hi jackeygor,

     

    Your understanding about PE and P routers is correct. Regarding use of BGP and OSPF, its not necessary to have both protocols , you just need one.

     

    Thanks,

    Suraj

    Please Mark My Solution Accepted if it Helped, Kudos are Appreciated too



  • 5.  RE: Why we need routing protocol in MPLS

    Posted 02-26-2015 05:32

    Hello,

     

    @jackeygor wrote:

     

     

    For example, RSVP MPLS

    We may need ISIS or OSPF, iBGP, RSVP and MPLS configured under protocol.

    I don't understand how the IGP work with MPLS.

     

     

    Speaking about "RSVP MPLS" in particular, one needs link-state IGP (not RIP, and not static routes) for loop prevention. Before sending out RSVP Path message, ingress LSR needs to build a loop-free ERO (Explicit Route Object).

    RSVP does not have own loop prevention capability, it uses that of link-state IGP.

    Otherwise, if there is a loop in the network, the RSVP LSP will never establish.

    HTH

    Thanks

    Alex

     



  • 6.  RE: Why we need routing protocol in MPLS

    Posted 02-26-2015 19:23

    Thanks!

     

    Can I conclude those things like below?

    OSPF: the link-state IGP, is to prevent loop in MPLS, build ERO, then generate different LSP

    RSVP/LDP: the signaling protocol, is to label the packet

    iBGP: not necessary in MPLS, but need it when exchange route between end client.

    MPLS: a term that conclude all the things



  • 7.  RE: Why we need routing protocol in MPLS

     
    Posted 02-26-2015 21:11
    Good Summary.

    Thanks,
    Suraj
    Please Mark My Solution Accepted if it Helped, Kudos are Appreciated too


  • 8.  RE: Why we need routing protocol in MPLS

    Posted 02-27-2015 01:51

    Hello,

     

    @jackeygor wrote:

    iBGP: not necessary in MPLS, but need it when exchange route between end client.

     

    iBGP Labeled Unicast (BGP-LU) is necessary in seamless MPLS.

    www.juniper.net/us/en/local/pdf/whitepapers/2000452-en.pdf

    HTH

    Thanks

    Alex



  • 9.  RE: Why we need routing protocol in MPLS

    Posted 03-01-2015 19:39

    Thanks but your article seems too difficult for meSmiley Sad

     

    But I do think that it is all fine if I just wanna have the simplest MPLS configuration even if no iBGP configured.