単一の NAT 対応ルーターで、一部のユーザーが NAT を使用し、他のユーザーが同じイーサネット インターフェイス上で独自の IP アドレスを使用し続けることができるようになりますか??

はい. This can be accomplished through the use of an access list describing the set of hosts or networks that require NAT. All sessions on the same host will be either translated or will pass through the router and not be translated.

Access lists, extended access lists, and route maps can be used to define rulesby which IP devices get translated. The network address and appropriate subnet mask should always be specified. The keyword anyshould not be used in place of the network address or subnet mask. With Static NAT configuration, when packet doesn’t matched with any STATIC rule configuration, packet will be sent through without any translation.