1、故障现象：
[root@localhost ~]# docker run -d -P httpd:centos
WARNING: IPv4 forwarding is disabled. Networking will not work.
解决方法：开启路由转发
cat /etc/sysctl.conf
net.ipv4.ip_forward=1
sysctl -p
需开启路由转发后再重启docker服务
Systemctl restart docker
2、故障现象：
[root@localhost tomcat]# docker run -d --name tomcat -p 80:8080 tomcat:v1
故障原因
大概率在docker启动的情况下关闭了防火墙
错误提示如下：
/usr/bin/docker-current: Error response from daemon: driver failed programming external connectivity on endpoint
tomcat (5f4478b0762c6c9e918688c1971d004626a29c96f39977459be48fd6d01fda46): (iptables failed: iptables --wait -t nat -A DOCKER -p tcp -d 0/0 --dport 80 -j DNAT --to-destination 172.17.0.3:8080 ! -i docker0: iptables: No chain/target/match by that name.
解决：实际原因：
docker服务启动时定义的自定义链DOCKER由于某种原因被清掉
重启docker服务及可重新生成自定义链DOCKER
```
systemctl restart docker
