The way to do it is to put the line: net.ipv4.tcp_challenge_ack_limit = 999999999
in a file in the /etc/sysctl.d directory named xxx.conf (replace xxx with your preferred name). Then run "sysctl -p xxx.conf" and the new value is installed in the kernel tree. My system had a value of 100 before I changed it. At boot the file will be read so the new value will be used then also. Check what is there now with: sysctl -a | grep net.ipv4.tcp_challenge_ack_limit You should see 999... after you run the sysctl -p command. When the kernel is fixed then you just need to delete the xxx.conf file and the next boot the default value will get used. ...Bob