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?

此 issue 未列出任何檔案、測試或進入點。先釐清必須支援哪些實體網路裝置與 CloudStack 網路功能，接著找出相關的整合點與設定範例。完成的條件包括已達成共識的範圍，以及為替換指定的系統虛擬機所記錄的設定案例。

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