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  • 1.  Question on MPLS MTU

    Posted 09-08-2022 10:02



    An MPLS LDP ping sweep returns an MTU result of 1488 bytes.



    lab@vmx-1:PE1# run ping mpls ldp sweep     

     88! 5044. 2568. 1328! 1948. 1640. 1484! 1564. 1524. 1504. 1496. 1492. 1488!

    --- lsp ping sweep result---

    Maximum Transmission Unit (MTU) is 1488 bytes


    Why is the MPLS MTU only 1488 bytes? Juniper says this is to accommodate 3 4-byte MPLS headers. But the MPLS ping is using only one MPLS header, so the MPLS MTU should be 1496 bytes. Why is it only 1488 bytes?




    Juniper Business Use Only

  • 2.  RE: Question on MPLS MTU

    Posted 09-12-2022 06:58
    Please check the following KB

    Most probably you have a "default" Maximum labels: 3 - so it exactly matches your result 3x4B=12, 1500 - 12=1488B