Consider my local network infrastructure map:


I've a device with a Virtual Machine that acts as a QOS manager/firewall to filter and prioritize traffic with complex rules that my main router cannot manage.

I would know if it's possible to route all connection to ZeroShell VM only when it's up and running, otherwise keeping the main router as default route for internet.

I need it because sometime the Firewall/QOS machine can go offline/under maintenance but i need that all devices continue to have internet access without manually change IP

  • Where is the Internet router connected? I don't see it in your diagram.
    – Ron Trunk
    Jan 26, 2015 at 16:39
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 11, 2017 at 3:31

2 Answers 2


you should check out VRRP or HSRP (when using Cisco)

http://en.wikipedia.org/wiki/Virtual_Router_Redundancy_Protocol http://en.wikipedia.org/wiki/Hot_Standby_Router_Protocol

In a nutshell:

2 routers will check availability, when the main disconnects, the backup takes over. These routers need to be in the same subnet doh, using 1 IP per router and 1 shared IP.

This shared IP is your default gateway.

  • Unfortunately my main router seems not implement both features. So i've thought using the routes and metrics: if the route to firewall is not available, then choose that with "higher metric". But i don't know if is it doable Feb 3, 2015 at 8:57
  • Metrics you can use on your WAN part, but to provide a single IP to the LAN part, you need these protocols. A client doesn't have prioritisation.
    – Bulki
    Feb 4, 2015 at 7:14

You could use a routing protocol like BGP and create a relationship with your router. Give your router preference to the VM, and let the routing protocol handle it.

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