[isaack]

A carrier deploying NAT might not be using CGNAT, and hence, in compliance with the spec, decide not to use the 100.64/16 space.

One requirement of CGNAT, for instance, requires that the carrier's router be able to handle "address crashes". [1]

[1] https://tools.ietf.org/html/rfc6598#section-4

[nickysielicki]

I think it says that you can use it even if you're not doing CGNAT, provided that you are a service provider.

> In particular, Shared Address Space can only be used in Service Provider networks OR on routing equipment that is able to do address translation across router interfaces when the addresses are identical on two different interfaces.

(edit: no, very clearly, "Devices MUST be capable of performing address translation when identical Shared Address Space ranges are used on two different interfaces." )

Also, is it wrong to assume that cellular networks are able to handle "address crashes" due to the inherent centralization that comes as a result of having clients maintain the same IP (and same connections) as the device hops from tower to tower? Maybe I don't understand the topics at play here...