Troubleshooting communication between containers and the external network
Packets can only pass between containers if the ip_forward parameter is set to 1. Usually, you will simply leave the Docker server at its default setting of --ip-forward=true and Docker will set ip_forward to 1 for you when the server starts up. To check the settings, use the following command:
# cat /proc/sys/net/ipv4/ip_forward 0 # echo 1 > /proc/sys/net/ipv4/ip_forward # cat /proc/sys/net/ipv4/ip_forward 1
By enabling ip-forward, users can make communication between containers and the external world possible; it will also be needed for inter-container communication if you are in a multiple bridge setup:
ip-forward = true forwards all the packets to/from the container ...
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