I'm creating tunnel interfaces to support up to a potential number of 2000 end point terminations. I have "heard" that there is an NHRP limitation of 254 per interface, but cannot find a specific reference. Is this a real and hard limit? Does it depend on the Cisco platform, the tunnel interface, the physical interface? Any reference would be much appreciated.
I don't think I would be brave enough to load it up that hard on a single hub.
I've used iWAN with more than 254 spokes, but I don't think iWAN uses NHRP any more unless talking to an older IOS (not sure). This design guide shows how to build an iWAN configuration to support 2,000 spokes. You'll need an ASR1k. I notice they have used four tunnels each with a /23 (which is what I have done - and it works fine).
If you are using IPSec as well watch out for the maximum number of SA's that the hub router is using can handle (unless you are using an ASR 1k ...).
Thanks for the input Philip. I'm not too concerned with the 2000 number, these are LTE backup links and statistically, we expect only a maximum of 200 to be terminated at any give time. I'm more interested in the actual NHRP limit, per tunnel interface, and the source reference document(s) that specific the limit.