Site to Site VPN with Fault Tolerence/Failover


I have a situation where I require an IPSEC tunnel between two sites. Site 2 is a small branch office with basic (ADSL) connectivity and Site 1 is the "main" office with SDSL and ADSL for redundancy should the SDSL fail. From Site 1, all traffic bound for the network will then be sent down another IPSEC tunnel to a supplier's Remote Server. See below for the basic premise (this is a rough idea and things can be moved about etc...)

I am considering specifying Cisco ASA devices as the firewalls for both sites for all connections. Would it be possible to employ something like HSRC to provide a backup at Site 1 should the SDSL go down? I suppose the key aims here are that Site 2 can somehow failover to initiate a VPN to the ASA behind the ADSL at Site 1. I will have a 21 subnet mask on all internet connections so can play with Class C routing if need be...

If I'm barking up the wrong tree with HSRC, is there another way I can acheive this without massive expenditure on Barracuda routers et al?

Many Thanks.
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Jody LemoineNetwork ArchitectCommented:
If you're looking at redundant VPN connections and transparent failover between them, I would investigate using Cisco routers rather than ASA devices.  The routers will give you the flexibility of tunnel-based VPNs which will allow you to use a routing protocol to provide load balancing or fast failover between the VPNs.  For the backup unit at site 1, you'll want a router as opposed to the ASA for HSRP functionality.

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