[c-nsp] ASR1k IOS recommendation

[Ramcharan, Vijay A]

For what it's worth, 
We recently upgraded a pair of ASR 1004 to latest available 15.0
software. These are used as large scale DMVPN hubs. We ran into a memory
leak on the previous 12.2.33 XNF software version that required some
tweaking of NHRP. We also saw as of about a month ago, on one hub, the
front end interface simply stop establishing sessions with spokes. That
required a reload to fix. At the time, the hubs were handling about 1500
spokes and had done so for over a month without problems. 

Still testing 15.0, not many spokes on it at this time. 
One fantastic feature addition to this new train is the "bgp
listen-range" command. That alone has cut down the configuration lines
in the router by a significant margin. There was one "cdp enable" line
that was left out of the configuration once the router had started up on
the new software but we found and fixed it. It occurred on both routers.
Once manually entered, it has remained despite subsequent reboots. 

We have not seen any issues with the new software but again, the routers
have only been running for about a week now on it and they are not
supporting production traffic at this time.  

Vijay Ramcharan