POP MPLS labels confusion-:

Discussion in 'CCENT / CCNA' started by shivaji, Jun 1, 2022.

  1. upload_2022-6-1_14-15-23.png

    IP packet comes to ingress router. Then MPLS header is attached to it.
    now, it becomes.

    MPLS hdr(contains label)|IP hdr|payload |

    Now while pushing, there could be 2 cases-:
    1) Only IP packet
    2) MPLS header+IP packet
    If there's only IP packet, push will add a label to IP packet
    If case 2), push will add a label to another MPLS label.
    So it's alright.

    Now for popping, there could be same 2 cases-:
    1) Only IP packet
    2) MPLS header+IP packet
    i) MPLS header+MPLS header+IP packet

    If there is only IP packet, there is no such thing as popping.
    If case 2) then pop will remove label from another MPLS label.
    If case 3) then pop will remove label from yet another MPLS label.

    So how does pop removes label from IP packet? I don't get that.
     
  2. dmarsh
    Honorary Member

    dmarsh Petabyte Poster

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    Look up stack or LIFO
     
  3. hmm i have idea about it. i have done a lot of stack stuffs in the past in various courses. am i missing sth? here the stack is for "label" only. so once labels are popped, there is nth else to pop as stack is empty.
     

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