New bridge network is not working well

Hello folks,
I am with a behavior, saying, strange. I am using Alpine Linux to run my Docker. I started my Docker and create my own network with the default command:
$docker network create mynet
What is happening is that when I attach a container at this network, the ports published have not been working properly. Then I reboot my entire system (Alpine) and all goes working well.
I tryed the following example:
$docker network create mynet
$docker run -d --name alpine1 --network mynet -p 8080:80 nginx:alpine
When I check
$docker network inspect mynet
All is ok, alpine1 is connected.
I tried access via web browser at 8080 port and nothing works.
After Alpine reboot, I tried again and all is ok, alpine1 is accessing normaly by port 8080.
Someone with similar a issue? Could help me?