Jumbo frame support in pfSense 2.2 within Hyper-V



  • I can't seem to get jumbo frames working on pfSense 2.2 within Hyper-V

    I can use jumbo frames between my Hyper-V host and another Windows guest OS within Hyper-V, but not pfSense.

    | When running on native hardware… | When running on within Hyper-V… |
    | If I run ifconfig em1 mtu 1508
    and then run route get [IP in local subnet]
    I see something like below, as you can see, the MTU is set correctly.

    route to: server
    destination: 10.7.2.0
          mask: 255.255.255.0
            fib: 0
      interface: em1
          flags: <up,done,pinned>recvpipe  sendpipe  ssthresh  rtt,msec    mtu        weight    expire
          0        0        0        0      1508        1        0</up,done,pinned>

    | If I run ifconfig hn1 mtu 1508
    and then run route get [IP in local subnet]
    I see something like below, as you can see, the MTU has not been set correctly.

    route to: server
    destination: 10.7.2.0
          mask: 255.255.255.0
            fib: 0
      interface: hn1
          flags: <up,done,pinned>recvpipe  sendpipe  ssthresh  rtt,msec    mtu        weight    expire
          0        0        0        0      1500        1        0</up,done,pinned>

    |

    Within this Hyper-V version of pfSense, running ifconfig hn1 does show an MTU of 1508, but without it also set within route, it's not possible to send anything larger than 1500 bytes.

    (FYI the reason for wanting 1508 is to use 'baby jumbo frames' to allow a full MTU 1500 over my PPPOE connection, you can read more here - https://forum.pfsense.org/index.php?topic=82939.0).



  • Do a reboot and it should be picked up automatically after reboot.



  • But the "ifconfig mtu" commands are temporary aren't they? Wouldn't they be reset to whatever setting I have in the GUI? (which also hasn't worked for me after a reboot).

    Any idea why I might be seeing different results on the native hardware (which was also without a reboot)

    M