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Description of problem:

NETMASK is not mentioned in our documentation (RHEL8.2):
~~~
$ man nm-settings-ifcfg-rh 2>/dev/null | grep 'NETMASK\>'
~~~

Version-Release number of selected component (if applicable):
RHEL8.2

Actual results:

Only PREFIX is mentioned:
~~~
$ man nm-settings-ifcfg-rh 2>/dev/null | sed -n '/Simple ethernet configuration with static IP/,/^$/p' 
           Simple ethernet configuration with static IP:
           TYPE=Ethernet
           BOOTPROTO=none
           IPADDR=10.1.0.25
           PREFIX=24
           GATEWAY=10.1.0.1
           DEFROUTE=yes
           IPV4_FAILURE_FATAL=no
           IPV6INIT=yes
           IPV6_AUTOCONF=yes
           IPV6_DEFROUTE=yes
           IPV6_PEERDNS=yes
           IPV6_PEERROUTES=yes
           IPV6_FAILURE_FATAL=no
           NAME=ethernet-em2
           UUID=51bb3904-c0fc-4dfe-83b2-0a71e7928c13
           DEVICE=em2
           ONBOOT=yes

~~~

Expected results:
The NETMASK option should also be mentioned.

Roughly my idea:

--- nm-settings-ifcfg-rh.5      2021-02-05 01:30:16.990194909 -0500
+++ new-nm-settings-ifcfg-rh.5  2021-02-05 01:30:08.190126502 -0500
@@ -242,6 +242,8 @@
 The UUID values in the config files must be unique\&. You can use
 \fIuuidgen\fR
 command line tool to generate such values\&. Alternatively, you can leave out UUID entirely\&. In that case NetworkManager will generate a UUID based on the file name\&.
+.br
+The PREFIX option (CIDR) can be replaced by the traditional NETMASK option\&.
 .SH "DIFFERENCES AGAINST INITSCRIPTS"
 .PP
 The main differences of NetworkManager ifcfg\-rh plugin and traditional initscripts are:

upstream:

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/commit/eebd9c2a86747b1879fae3d538452c60388a411b

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: NetworkManager and libnma security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:1574