If you have correctly installed the MPTCP-kernel and configured the routing tables as needed, you can start using MPTCP


This server ( is running the latest build of our kernel. Thus, every time you connect to this server you will be using MPTCP.

Download some files

You can also visit to see how well your network supports MPTCP on different port-numbers.

No MPTCP at all

If it looks like you don't use MPTCP at all, please check these points:

  • Are you using a kernel with MPTCP?
    • sudo dmesg | grep MPTCP
  • Is MPTCP enabled?
    • sysctl net.mptcp.mptcp_enabled
  • Does the application create an MPTCP connection?
    • tcpdump -n -i <interface> tcp | grep mptcp
  • Is MPTCP blocked somewhere between the client and the server?
    • Visit and check the different ports
    • sudo tracebox -p 'IP/tcp{dst=443}/MPCAPABLE' (See Tools)
    • Feel free to report such issues to the network owner (ISP, etc.): most of the time, it is a mistake or due to some default configurations.

MPTCP only with one path

If MPTCP is used but only with one path, please check:

  • Did you configure a path manager on the client side to establish more subflows?
  • Did you configure a path manager on the server side to announce more available IP addresses?
  • Did you configure the routing?
  • Is MPTCP blocked on some paths?
    • See above about tracebox.