In a nat instance , already add 8120 address for private user to access Internet .
but only 7170 users can access Internet .other user cannot access .
When executed command "display aaa online-fail-record " get this error :Add nat user data fail(Port PreAlloc Fail)

Check nat instance configuration ,we find port-range is 8192 .but this command just for port pre-allocation.
And about the facing error :Add nat user data fail(Port PreAlloc Fail) ,because public address port not enough for user online.
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Public address port not enough for user online.

about other users cannot online ,there are two ways to solve it :
1、 customer need extension the public address pool for the online-fail nat instance
2、 modify port-range value , please refer below , need online user offline release resource , then new user can online .
[HUAWEI] nat instance 1
[HUAWEI-nat-instance-1] undo port-range
[HUAWEI-nat-instance-1] port-range 4096
[HUAWEI-nat-instance-1]quit
[HUAWEI]aaa
[HUAWEI-aaa]cut access-user domain domain-name /// must kick off user offline , this configuration can work .
Or if not cut users offline , must wait user online again , this configuration can work .