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Max Frame Size and IP-MTU in AOS/AOS-CX with a MacSec interface in use over a ISP/L2tunnel

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  • 1.  Max Frame Size and IP-MTU in AOS/AOS-CX with a MacSec interface in use over a ISP/L2tunnel

    Posted Jul 24, 2022 06:44 AM

    ISP/mpls networks, MTU limitation vs. AOS/CX and MACSec

    Based on the ISP requirement/limitation they can only handle a Max Frame Size: 9192;    

    Inside the mpls network.

    sh jumbos (AOS)

    Configured :  Max Frame Size :  9216      IP-MTU :  9198

    In Use     :      Max Frame Size :  9216      IP-MTU :  9198

     

    The CX states on a Physical interface:

    SW(config-if)# mtu

    • BYTES The MTU value in bytes in the range <46-9198> (Default: 1500)

    The CX states on a SVI:

    SW(config-if-vlan)# ip mtu

    • <68-9198> The IP payload MTU value in bytes (Default: 1500)

     

     What should the Max Frame Size/IP-MTU be set to on the SVI and or Physical,

    for all MacSec frames to be traversed, understanding there is an overhead for the MacSec.



  • 2.  RE: Max Frame Size and IP-MTU in AOS/AOS-CX with a MacSec interface in use over a ISP/L2tunnel
    Best Answer

    Posted Jul 25, 2022 01:52 AM
    MacSec adds a 32byte overhead to the packets. Based on the mpls network MTU limitation , MTU size can be set in AOS-CX switches i.e 9192-32

    ------------------------------
    Shobana
    Aruba
    ------------------------------

    Original Message


  • 3.  RE: Max Frame Size and IP-MTU in AOS/AOS-CX with a MacSec interface in use over a ISP/L2tunnel

    Posted Jul 25, 2022 01:59 AM
    Thanks
    Original Message


  • 4.  RE: Max Frame Size and IP-MTU in AOS/AOS-CX with a MacSec interface in use over a ISP/L2tunnel

    Posted Jul 25, 2022 02:21 AM

    However is it necessary to decrease the OS,(2930F 's) Max Frame Size of 9216 equally ?,

    Alternatively, will this do the trick on a OS switch:

    • Configured :
      • Max Frame Size : 9216      IP-MTU :  9160

     

    • And OS-CX:
      • MTU & IP MTU: 9160

    Original Message