Visit Our UNIX and Linux User Community

DHCP server discover

Thread Tools Search this Thread
Special Forums IP Networking DHCP server discover
# 1  
Old 11-14-2011
DHCP server discover

I need a script to scan the surrounding DHCP servers. I want to know how many dhcp servers are there on my connected etnernet.
# 2  
Old 11-14-2011
Mrm. A script won't help you. Something like nmap would be your tool of choice. I'm thinking this is what you want to use (run as root):
nmap -oN /tmp/dhcp-discovery.txt -sU -p 67,547

Change the portion in blue to match your subnet/bits-in-mask.

Then grep the results:
grep -B4 open /tmp/dhcp-discovery.txt

If your grep doesn't support "-B", try:
egrep "(^Interesting)|( open)" /tmp/dhcp-discovery

And you'll see output like:
Interesting ports on
Interesting ports on
67/udp open|filtered dhcps
Interesting ports on
Interesting ports on
Interesting ports on

And the line in red is the one you're interested in.

Last edited by otheus; 11-14-2011 at 10:18 AM.. Reason: corrections, expounding on output
# 3  
Old 11-17-2011
Thanks dud, I have tried your recommendation. I got a lot of ip addresses on my network as result. I didn't understand that which one is dhcp offer,discover or inform packages. It only shown dhcp open or closed. I'm just looking for the ip address that the dhcp packages are offered. only offered packages not discover or inform packages.

I found script that is searching dhcp offer packages. DHCP offer packages mean DHCP server. Smilie

Script is on related link. roguedetector - Revision 29: /trunk/RogueDetect It have dependency : libconfig, libnet, libnet-devel, libpcap. You can read README file.

Wireshark is searching DHCP offer, discover and inform packages. We must write bootp on filter box.

Previous Thread | Next Thread
Test Your Knowledge in Computers #406
Difficulty: Medium
Cygwin was originally developed by Cygnus Solutions, which was later acquired by Microsoft.
True or False?

10 More Discussions You Might Find Interesting

1. Ubuntu

Ubuntu Server in VM - DHCP Server not working

Hello. Doing my first steps in Linux and while trying to configure a DHCP server in Linux i encountered some problems: TOPOLOGY: - Laptop with Windows 8.1 - VM Player 12 with Linux installed (Ubuntu Server 14.04) - ICS-DHCP-SERVER installed and running - Another LAPTOP conected to a... (1 Reply)
Discussion started by: Portuguevos
1 Replies

2. Solaris

Solaris DHCP Server

I need to find out the MAC address of an IP leased from DHCP server . For Eg:-i need to know the MAC of the below mentioned IP at the below mentioned time . IP : Date :Sunday July 2nd 2011 Time : 14.07.2011 OS -Solaris 10 Vital QIP IP management software using to... (0 Replies)
Discussion started by:
0 Replies

3. Red Hat

DHCP Server address

Where can you find your DHCP Server address? I checked all of the files that this mentioned with no luck. Quick HOWTO : Ch08 : Configuring the DHCP Server - Linux Home Networking (6 Replies)
Discussion started by: cokedude
6 Replies

4. Solaris

Is a Solaris dhcp server better than windows?

hi, we are moving to dhcp from a static ip and i'm thinking which should best be the DHCP server? i have a windows 2003 server and a solaris 10 running on sun's m5000 server. Note to pinoy43v3r: Your avatar was NSFW. We changed it. (5 Replies)
Discussion started by: pinoy43v3r
5 Replies

5. Solaris

Exporting DHCP to backup server

Hi just looking for some advise on the best way to set-up a passive dhcp server in solaris. Was thinking of exporting the dhcp data/macros etc to a separate server to use as a backup that will be activated when the main dhcp server goes down Any hints/tips etc greatly appreciated (1 Reply)
Discussion started by: eeisken
1 Replies

6. IP Networking

DHCP server also acting as relay

Hi. I want to use the DHCP server that comes with vxWorks 6.4. The DHCP server implementation has a table that contains addresses of DHCP servers that will receive a copy of all the client requests that the local server gets, thus the server acts as a dhcp relay at the same time. Can anyone... (4 Replies)
Discussion started by: tomwolf
4 Replies

7. Solaris

couldn't contact the DHCP server

hi when i configure for DHCP in my solaris it says not able to contact dhcp server.. what might be the problem( is there any problem in recognizing my hostname by DHCP Server)? can any one explain thanks in advance (1 Reply)
Discussion started by: srikanthg
1 Replies

8. AIX

AIX & DHCP Server

Dear people, i have a problem with my DHCP Server based on an AIX. I try to evaluate my dhcpsd.log and find some errors. But now i'm missing a documentation about this errors. For example "protocol_spsm: address check failed". i would be happy if someone could tell me where to find a... (0 Replies)
Discussion started by: ektoplasma2000
0 Replies

9. IP Networking

DHCP server question

hi all... i have a question about of the dhcp server.... how i can configurate 3 vlans on the server....? thank you (5 Replies)
Discussion started by: chanfle
5 Replies

10. UNIX for Dummies Questions & Answers

DHCP Server Suggestions

I need to setup a DHCP server in our office for Macs, Windows (98/ME/NT/2000) Linux and Unix servers and workstations. We want it on a Unix server, but I'm unsure what is out there. The Unix world is new to me, so any suggestions would be appreciated. Thanks! Corey (2 Replies)
Discussion started by: coreyhead
2 Replies

Featured Tech Videos