[c-nsp] Rogue NAT gateways

[Dan Letkeman]

Wondering if anyone has any tricks for disabling the use of any NAT
gateways?  I know the best way is to remove it physically, but in the
case of guest access and mobile devices its sometimes difficult to do
so.  Now that many devices can act as a hotspot, some of these devices
are becoming difficult to find.  I have looked into ACL's with ttl
requirements, but I could not seem to get it to work like I wanted.