This is the validated design guide.
http://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Feb2016/CVD-IWANDesignGuide-FEB16.pdf
Things that make iWAN rock solid reliable:
- All routers have a public IP address directly on their outside interface - don't place them behind something else doing NAT.
- All routers running 15.4(3)M4 or better.
- Use Cisco 880 or higher routers. 880 and 890's should have advanced IP. 1900, 2900, 4000 series routers should have an AppX licence.
- All routers under SmartNet so you can upgrade their software or get support from Cisco TAC directly.
I have often violated the rules above, but I always strive for them. Like I say "rock solid reliable" if you follow them.
