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How to check DHCP server information

More than 1 year has passed since last update.

Prerequiste

  • nmap
yum install nmap

Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base: ftp.nara.wide.ad.jp
 * elrepo: ftp.yz.yamagata-u.ac.jp
 * epel: ftp.jaist.ac.jp
 * epel-debuginfo: ftp.jaist.ac.jp
 * epel-source: ftp.jaist.ac.jp
 * extras: ftp.nara.wide.ad.jp
 * updates: ftp.yz.yamagata-u.ac.jp
Resolving Dependencies
--> Running transaction check
---> Package nmap.x86_64 2:6.40-7.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

Installing:
 nmap                               x86_64                               2:6.40-7.el7                                base                               4.0 M

Transaction Summary
Install  1 Package

Total download size: 4.0 M
Installed size: 16 M
Is this ok [y/d/N]: y
Downloading packages:
nmap-6.40-7.el7.x86_64.rpm                                                                                                             | 4.0 MB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : 2:nmap-6.40-7.el7.x86_64                                                                                     1/1 
  Verifying  : 2:nmap-6.40-7.el7.x86_64                                                                                     1/1 
Installed:
  nmap.x86_64 2:6.40-7.el7                                                                                                                                    
Complete!

How to check

  • nmap --script broadcast-dhcp-discover
nmap --script broadcast-dhcp-discover

Starting Nmap 6.40 ( http://nmap.org ) at 2018-04-13 09:47 JST
Pre-scan script results:
| broadcast-dhcp-discover: 
|   IP Offered: XXX.XXX.XXX.XXX
|   DHCP Message Type: DHCPOFFER
|   Server Identifier: YYY.YYY.YYY.YYY
|   IP Address Lease Time: 0 days, 0:05:00
|   Subnet Mask: 255.255.255.0
|   Time Offset: 32400
|   Router: ZZZ.ZZZ.ZZZ.ZZZ
|   Domain Name Server: 
|   Domain Name: 
|   Broadcast Address: 
|_  NTP Servers: 
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 0.23 seconds
tkprof
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