Multiple Default Gateways

Simple WAN - 3 sites, one main and two remote sites connected via a MetroE with Cisco routers.  IP address of cisco router is at a particular site...

Each site has sonicwall to ISP internet.  For this example, sonicwall is  DHCP is handled by sonicwall and default gateway for network is  

Is there anyway to have the default gateway change automatically should the internet go down at a remote site.  For example, Internet goes out at the 1.x network.  If I manually change the default gateway to 1.253, then devices would use MetroE to access Internet at main site plus all other devices over the MetroE.

I need this to happen automatically.  I could make the internal MetroE cisco router as the default route but again, on the fly how would I route "unknown" traffic across the MetroE should the local Internet go down?

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Jason JohanknechtIT ManagerCommented:
Are you asking if your WAN goes down on site A, that site B or C would somehow solve the problem?  The routers can be connected by site-2-site VPN. Without a failover ISP on the failed location, there is no way the VPN could stay up to keep the sites connected.  The Gateway is your router for each site.  What model Cisco routers?
RFloyd30Author Commented:
I should have be clearer - my apologies.

No VPN.   Cisco 1800 series routers connect site to site via a MetroE circuit - old school like a point to point.  The provider of the MetroE hands it off with no IP's so we build the WAN and the LAN and handle all routing.  

The Sonicwall connects each site to their own Internet.   The Sonicwall is currently the default gateway for each site and has a route statement that points data to the MetroE to go to a specific network (ie main site network).  

What i'm asking is that if the remote site's Internet goes out, how can we make ALL traffic go across MetroE (which is still live) without manually changing the default gateway from the sonicwall to the cisco 1800 router?
Jody LemoineNetwork ArchitectCommented:
One option is to configure the SonicWALL and the Cisco 1800 for VRRP and have them share the IPv4 address of the default gateway. Make sure that the SonicWALL has better priority so that it will hold the gateway address as long as it's active. Should it go down or lose connection to the LAN, the Cisco 1800 will take over the gateway address. If you configure preempting on VRRP, the SonicWALL will take the address back when it is reachable again.

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Jason JohanknechtIT ManagerCommented:
If you have a Point-2-Point (P2P) fibre or T1 or whatever network joining everything that is fine.  But what is the bandwidth of that P2P?  Do you  have support contract with Sonicwall?  Contact them directly on this and they should be able to tell you if it is possible and how.
N. SpearsSr.Net.EngCommented:
I agree with Jody. VRRP is in the right direction. It offers the redundancy you need if your Sonicwall fails and will have your traffic route through the Metro Router. Additionally I would add a method of detecting the failure of the ISP on the Sonicwall. I believe Sonics have static route probes that you can configure to do reachability testing and will remove the static route if it fails.
RFloyd30Author Commented:
Understood and easy enough.

Very much appreciate the replies!

Take care,
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