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.

Beginne damit, das Isolated-Netzwerk mit der Routed Dynamic virtual-router-Implementierung nachzuverfolgen und es mit der natted virtual-router-Implementierung zu vergleichen, die keepalived verwendet. Erledigt ist die Aufgabe, wenn aktive/passive virtual-router Redundanz bereitstellen, sodass ein Host- oder VM-Ausfall das Standard-Gateway, DHCP, DNS oder die Netzwerkverbindung nicht unterbricht.

Vom Indexierungsmodell aus dem Issue-Text verfasst.