Working with Tagged Traffic MPLS/QinQ

To support tagged MPLS or QinQ traffic, it is necessary to change the MTU.
For QinQ, an MTU of 1508 is sufficient, while for MPLS, the MTU depends on the depth of the label stack.
Additionally, some implementations of the ISIS protocol use more MTU than specified in the network equipment settings.

Changing MTU

DPI provides the ability to increase the MTU to 1518 without changing other settings.
Settings depend on the cards used.

Intel Cards

In the configuration file fastdpi.conf set the parameter snaplen=<mtu_size>

Mellanox Cards

  1. In the configuration file fastdpi.conf set the parameter snaplen=<mtu_size>
  2. Set on the network interfaces:
    ifconfig: sudo ifconfig eth0 mtu 1500

    or

    nmcli: sudo nmcli connection modify team1-port1 802-3-ethernet.mtu 9000

    or

    /etc/sysconfig/network-scripts/ifcfg-if1
     
    TYPE=Ethernet
    MTU=4096
    PROXY_METHOD=none
    BROWSER_ONLY=no
    IPV6INIT=no
    IPV6_DEFROUTE=yes
    IPV6_FAILURE_FATAL=no
    IPV6_ADDR_GEN_MODE=default
    NAME="if1"
    UUID=53b84dd0-3c5e-3397-b764-7ad40f1ad14c
    DEVICE=enp129s0f0np0
    ONBOOT=yes
    AUTOCONNECT_PRIORITY=-999
    IPV6_DISABLED=yes
To see the list of all connections:
nmcli con show

:!: A significant MTU change may lead to decreased performance and may require changes to other driver settings and internal DPI service settings.
If a more significant MTU change is necessary, consult with technical support.