Tc Seems To Have No Effect On The NIC’s

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Hello all,

We have installed this network testing environment:

which seems pretty nice overall.

It allows you to artificially degrade your network performance by issuing tc commands to directly affect your networking.

I have it set up on two CentOS 6 machines – one a Dell server, one a VirtualBox VM. The tc syntax seems OK, it seems to all make sense – only it seems to have no effect whatsoever on the actual network performance.

Hence the question: is there a known issue with tc? Am I perhaps missing some kernel modules, or do I perhaps now have some kernel parameters set correctly?

Any insight will be helpful.

Thanks in advance,



One thought on - Tc Seems To Have No Effect On The NIC’s

  • Hi Boris,

    Maybe it’s just not matching your traffic and thus putting it in the main class, lets say.

    You can check how it’s going on with
    tc -s qdisc show dev DEV
    tc -s class show dev DEV
    Both have some interestings stats that you can watch using watch -d and check through where your traffic is flowing.

    If the numbers you want to are not changing, you’re probably missing the tc filters for matching them.