怎样知道ECS实例公网IP的子网掩码？

CIDR表示方法：IP地址/网络ID的位数

那要怎么才能知道公网IP的网络ID位数呢？

https://stackoverflow.com/a/41922845/13095968

这个回答中说，可以查找RIR的数据库

olawod@name:~$ whois -T route 我的公网ip
% This is the RIPE Database query service.
% The objects are in RPSL format.
%
% The RIPE Database is subject to Terms and Conditions.
% See http://www.ripe.net/db/support/db-terms-conditions.pdf

% Note: this output has been filtered.
%       To receive output for a database update, use the "-B" flag.

%ERROR:101: no entries found
%
% No entries found in source RIPE.

% This query was served by the RIPE Database Query Service version 1.97 (BLAARKOP)

olawod@name:~$ whois 我的公网ip
% [whois.apnic.net]
% Whois data copyright terms    http://www.apnic.net/db/dbcopyright.html

% Information related to '120.24.0.0 - 120.27.255.255'

% Abuse contact for '120.24.0.0 - 120.27.255.255' is 'ipas@cnnic.cn'

inetnum:        120.24.0.0 - 120.27.255.255
netname:        ALISOFT
descr:          Aliyun Computing Co., LTD
descr:          5F, Builing D, the West Lake International Plaza of S&T
descr:          No.391 Wen'er Road, Hangzhou, Zhejiang, China, 310099
country:        CN
admin-c:        ZM1015-AP
tech-c:         ZM877-AP
tech-c:         ZM876-AP
tech-c:         ZM875-AP
mnt-by:         MAINT-CNNIC-AP
mnt-irt:        IRT-CNNIC-CN
status:         ALLOCATED PORTABLE
last-modified:  2014-07-30T02:24:03Z
source:         APNIC

irt:            IRT-CNNIC-CN
address:        Beijing, China
e-mail:         ipas@cnnic.cn
abuse-mailbox:  ipas@cnnic.cn
admin-c:        IP50-AP
tech-c:         IP50-AP
auth:           # Filtered
remarks:        Please note that CNNIC is not an ISP and is not
remarks:        empowered to investigate complaints of network abuse.
remarks:        Please contact the tech-c or admin-c of the network.
mnt-by:         MAINT-CNNIC-AP
last-modified:  2017-11-01T08:57:39Z
source:         APNIC

person:         Li Jia
address:        NO.969 West Wen Yi Road, Yu Hang District, Hangzhou
country:        CN
phone:          +86-0571-85022088
e-mail:         jiali.jl@alibaba-inc.com
nic-hdl:        ZM1015-AP
mnt-by:         MAINT-CNNIC-AP
last-modified:  2014-07-30T02:02:01Z
source:         APNIC

person:         Guoxin Gao
address:        5F, Builing D, the West Lake International Plaza of S&T
address:        No.391 Wen'er Road, Hangzhou City
address:        Zhejiang, China, 310099
country:        CN
phone:          +86-0571-85022600
fax-no:         +86-0571-85022600
e-mail:         anti-spam@list.alibaba-inc.com
nic-hdl:        ZM875-AP
mnt-by:         MAINT-CNNIC-AP
last-modified:  2014-07-30T01:56:01Z
source:         APNIC

person:         security trouble
e-mail:         cloud-cc-sqcloud@list.alibaba-inc.com
address:        5th,floor,Building D,the West Lake International Plaza of S&T,391#Wen’er Road
address:        Hangzhou, Zhejiang, China
phone:          +86-0571-85022600
country:        CN
mnt-by:         MAINT-CNNIC-AP
nic-hdl:        ZM876-AP
last-modified:  2013-07-08T02:56:02Z
source:         APNIC

person:         Guowei Pan
address:        5F, Builing D, the West Lake International Plaza of S&T
address:        No.391 Wen'er Road, Hangzhou City
address:        Zhejiang, China, 310099
country:        CN
phone:          +86-0571-85022088-30763
fax-no:         +86-0571-85022600
e-mail:         guowei.pangw@alibaba-inc.com
nic-hdl:        ZM877-AP
mnt-by:         MAINT-CNNIC-AP
last-modified:  2013-07-09T01:34:02Z
source:         APNIC

% Information related to '120.26.0.0/15AS37963'

route:          120.26.0.0/15
descr:          Addresses from CNNIC
country:        CN
origin:         AS37963
mnt-by:         MAINT-CNNIC-AP
last-modified:  2016-04-07T03:20:01Z
source:         APNIC

% This query was served by the APNIC Whois Service version 1.88.15-46 (WHOIS-NODE1)

因此网络号15位，子网掩码255.254.0.0，对吗？