How to integrate cloustack with physical network devices to replace system virtual machines

### The required feature described as a wish

CloudStack's network functions and management are usually implemented through System Virtual Machines (SVMs), especially network-related functions such as routing, NAT, VPN, DHCP, etc. How can we integrate with physical network devices to replace system virtual machines? Are there any relevant configuration cases?

该 issue 没有提及任何文件、测试或入口点。首先明确必须支持哪些物理网络设备和 CloudStack 网络功能，然后确定相关的集成点和配置示例。完成的标准包括：达成一致的范围，以及为替换指定的系统虚拟机而记录的配置案例。

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