Redundant Virtual Router support in Isolated network with network mode set to Routed Dynamic

### Feature request

At the moment, the _Isolated network with Routed Dynamic network mode_ only supports running with a single virtual router. This means in the event of a host or VM failure, there will be a network outache of about 5 to 7 minutes. This virtual router is the default gateway of all VM's in this network, so the impact can mean downtime and loss of services (DHCP, DNS, networking).

### Solution

It would be great to have the same implementation as the "natted" virtual router type where keepalived is used between an active and passive virtual router in order to give redundancy.

首先跟踪采用 Routed Dynamic virtual-router 实现的 Isolated 网络，并将其与使用 keepalived 的 natted virtual-router 实现进行比较。完成的标准是 active/passive virtual-router 提供冗余，使主机或 VM 故障不会中断默认网关、DHCP、DNS 或网络。

由索引模型根据 Issue 内容生成。