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pufferfish
Asked: 2010-08-19 00:45:07 +0800 CST

Command line program to test DHCP service

  • 772

Is there a simple ping-like command to test whether a DHCP service is running on a network? ...on Linux

linux ubuntu dhcp

9 Answers

  1. Based on this answer, assuming you have installed nmap (sudo apt install nmap):

    sudo nmap --script broadcast-dhcp-discover

    Add the -e $interface option if you have more than one network interface. (For example: nmap --script broadcast-dhcp-discover -e eth0)

    Sample output:

    Starting Nmap 7.01 ( https://nmap.org ) at 2017-09-27 17:40 CEST
Pre-scan script results:
| broadcast-dhcp-discover: 
|   Response 1 of 1: 
|     IP Offered: 192.168.81.94
|     DHCP Message Type: DHCPOFFER
|     Server Identifier: 192.168.81.2
|     IP Address Lease Time: 5m00s
|     Subnet Mask: 255.255.255.0
|     Router: 192.168.81.2
|     Domain Name Server: 192.168.81.2
|     Domain Name: example.lan
|     NTP Servers: 192.168.81.10, 192.168.81.2
|     NetBIOS Name Server: 192.168.81.10
|_    NetBIOS Node Type: 8
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 0.66 seconds

    Or this output on a different network, with nmap v. 6 :

    Starting Nmap 6.00 ( http://nmap.org ) at 2017-09-27 17:42 CEST
Pre-scan script results:
| broadcast-dhcp-discover: 
|   IP Offered: 192.168.4.101
|   DHCP Message Type: DHCPOFFER
|   Server Identifier: 192.168.4.1
|   IP Address Lease Time: 7 days, 0:00:00
|   Subnet Mask: 255.255.255.0
|   Time Offset: 7200
|   Router: 192.168.4.1
|   Domain Name Server: 208.91.112.53, 208.91.112.52
|   Renewal Time Value: 3 days, 12:00:00
|_  Rebinding Time Value: 6 days, 3:00:00
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 1.15 seconds
    • 90
  2. Best Answer

    Even if you don't use a Nagios monitoring server, you can grep the check_dhcp binary or compile it from source and use the check to test a DHCP-Server. E.g.

    ./check_dhcp -v -s <dhcp_server_address> -r <expected_ip_address> -m <mac_address_touse>
    • 17

  3. or you can try dhcpcd in test mode:

    dhcpcd -T eth0
    • 15

  4. dhcpdump is good for sniffing and displaying DHCP packets on the network.

    E.g.

    # dhcpdump -i eth0
---------------------------------------------------------------------------

  TIME: 2015-11-27 11:41:37.379
    IP: 0.0.0.0 (0:11:b9:5:0:b8) > 255.255.255.255 (ff:ff:ff:ff:ff:ff)
    OP: 1 (BOOTPREQUEST)
 HTYPE: 1 (Ethernet)
  HLEN: 6
  HOPS: 0
   XID: abce9327
  SECS: 0
 FLAGS: 0
CIADDR: 0.0.0.0
YIADDR: 0.0.0.0
SIADDR: 0.0.0.0
GIADDR: 0.0.0.0
CHADDR: 00:11:b9:05:00:b8:00:00:00:00:00:00:00:00:00:00
 SNAME: .
 FNAME: .
OPTION:  53 (  1) DHCP message type         1 (DHCPDISCOVER)
OPTION:  57 (  2) Maximum DHCP message size 576
OPTION:  55 (  4) Parameter Request List      1 (Subnet mask)
                          3 (Routers)
                         28 (Broadcast address)
                          6 (DNS server)

---------------------------------------------------------------------------

    You can use it in conjunction with another tool to do DHCP requests, or just use it to watch PCs/devices query DHCP.

    • 12

  5. Why not just make a DHCP request? 

    dhclient

    For verbose output use:

    dhclient -v

    • 7

  6. I wrote a DHCP test client program a while ago, works on Windows and POSIX:

    https://github.com/CyberShadow/dhcptest

    • 6

  7. There is a program called dhcping (with just one p)

    • 4

  8. if you use nagios you could monitor it with check_dhcp

    • 0

  9. On Debian-Ubuntu systems:

    dhcpd -f

    gives good feedback and tests the configuration.

    On RH systems try:

    /etc/rc.d/init.d/dhcpd configtest
    • 0