You can resolve issues caused by abnormal kernel parameter configurations in a NAT environment by fixing the tcp_tw_recycle and tcp_timestamps parameters. These issues include failure to connect to the instance via SSH, abnormalities when you access HTTP services on the instance, and connection resets when you use the telnet command for network testing.

Causes

Due to the local network accessing the internet via NAT sharing and abnormal Linux system-related kernel argument configuration, the involved abnormal kernel arguments include tcp_tw_recycle and tcp_timestamps.

Procedure

Execute the following commands in sequence to view whether the current kernel configuration is normal.

cat /proc/sys/net/ipv4/tcp_tw_recycle
cat /proc/sys/net/ipv4/tcp_timestamps

If the result is 1, the configuration is abnormal. Follow the following steps to fix the tcp_tw_recycle and tcp_timestamps parameters.

If the result is 0, the configuration is normal. There is no need to fix the tcp_tw_recycle and tcp_timestamps parameters. Submit a ticket or contact your account manager for technical support.

Execute the following command to add kernel arguments in the /etc/sysctl.conf configuration file.

net.ipv4.tcp_tw_recycle=0
net.ipv4.tcp_timestamps=0

Execute the following command to make the configuration take effect.

sysctl -p

Last updated: 2026.04.13 16:50:03

Public security network record in Beijing: No. 11010802032137