You may need to reconfigure the firewall if you add a new machine to your network.

如果在网络中增加新计算机，可能就得重新设定防火墙。

《牛津词典》

youdao

Ensure the iptables is initialized with your new configurations when the virtual machine reboots and not with the default setup. You can issue the following commands to save the firewall rules.

确保iptables在虚拟机重启时用新配置而不是默认设置进行初始化。

youdao

But I don't really know about how long it would take people to hack, like, the general firewall

但我不知道人们具体要用多长时间才能穿过防火墙，

理想是当密码专家 - SpeakingMax英语口语达人

Most firewall vendors include a VPN application as a part of the firewall itself.

FORBES: Teach Your Boss to Speak Security: Economy of Mechanism

So why not deploy an intelligent appliance behind the router and in front of the firewall?

FORBES: Clean That Network Traffic

Any change to the complex rule set in the firewall could have unintended consequences.

FORBES: Reduce Policy Complications to Enhance Security