We have 4 1410 bridges between 2 buildings (point to point). each set of bridges sits behind an 1841 router that is helping us with load balancing across both bridges and doing VPN tunnels. Anytime we do a file copy (30mb or higher) the CPU on the router jumps up to 60+% and the performance dies on the bridge, even EIGRP hellos are not making it through so it removes the neighbor and causes a couple second outage. I am not sure if it just the 1841 not being able to handle this or something else. I am using CEF per-destination with EIGRP and doing 3des-md5 tunnels between each set of bridges. It seems there is really no config needed for cef per-destination, just turning on cef takes care of that. If it is the router, what router can handle 108mb/s of load-balanced, vpn encrypted traffic.
Hi, as you noticed, the problem is not the VPN, but the CPU performance itself. The 1841 is a small wan router and is not apt for sustained LAN to LAN usage. I was suggesting a L3 device because it does wire-speed routing, but of course doesn't do VPN.
Attached a document with info on router performance. The embedded VPN module is adequate for most uses and does not requires upgrade.
Hope this helps, please rate post if it does!