Routing

last person joined: 4 days ago 

Ask questions and share experiences about ACX Series, CTP Series, MX Series, PTX Series, SSR Series, JRR Series, and all things routing, including portfolios and protocols.

  • 1.  entries in mpls.0

    Posted 10-21-2012 09:24

    HI,experts

     

     I use ldp to bulid the lsp

     

    mpls.0: 8 destinations, 8 routes (8 active, 0 holddown, 0 hidden)
    + = Active Route, - = Last Active, * = Both

    0                  *[MPLS/0] 01:33:11, metric 1
                          Receive
    1                  *[MPLS/0] 01:33:11, metric 1
                          Receive
    2                  *[MPLS/0] 01:33:11, metric 1
                          Receive
    299808             *[LDP/9] 01:02:44, metric 1
                        > to 192.168.12.2 via em1.12, Pop      
    299808(S=0)        *[LDP/9] 01:02:44, metric 1
                        > to 192.168.12.2 via em1.12, Pop      
    299840             *[LDP/9] 00:46:09, metric 1
                        > to 192.168.13.3 via em1.13, Pop      
    299840(S=0)        *[LDP/9] 00:46:09, metric 1
                        > to 192.168.13.3 via em1.13, Pop      
    299856             *[LDP/9] 00:36:09, metric 1
                        > to 192.168.13.3 via em1.13, Swap 299856
                          to 192.168.12.2 via em1.12, Swap 299872

     

     

     

    a little confused by this output

     

    299808             *[LDP/9] 01:02:44, metric 1
                        > to 192.168.12.2 via em1.12, Pop      
    299808(S=0)        *[LDP/9] 01:02:44, metric 1
                        > to 192.168.12.2 via em1.12, Pop    

     

     

    they are the same ,(S=0) is the only difference

     

     

    what is the difference between these 299808 and 299808(s-0)?



  • 2.  RE: entries in mpls.0

    Posted 10-21-2012 18:05

    Hi,

     

    S represents Label- stack depth.

     

    299840 - Label Stack Depth is 1. That means the packets come with one label will be treated according to this entry.

     

    299840(S=0)  - Denotes , the Label Stack depth is not equal 1. That means the packets come with more than one label will be treated according to this entry.

     

    For both cases, the operation pops the top label off the stack.

     

    These two entries will appear in the penultimate routers.

     

    Regards,

    Moses N



  • 3.  RE: entries in mpls.0
    Best Answer

    Posted 10-21-2012 22:33

    299840 - Label Stack Depth is 1. That means the packets come with one label will be treated according to this entry.

     

    299840(S=0)  - Denotes , the Label Stack depth is not equal 1. That means the packets come with more than one label will be treated according to this entry.

     

    every lable will have these 2 entries in penultimate routers,right?

    if the operation is pop this lable,why there is 2 entries to handle this.................



  • 4.  RE: entries in mpls.0

     
    Posted 10-23-2012 17:28

    Hi Robbie,

     

    These entries are mainly for the forwarding-plane on how they have to handle the packets. From user point of view, it should be transparent.

     

    Say, for ethernet outgoing interface, if the MPLS packet has S=1, then the ether-type has to be set to 0x0800 before forwarding. Similarly for S=0, then it has to be set to 0x8847

     

    Regards

    Surya