Sorry for the top post
1. Lease Request - The client sends a broadcast requesting an IP address
2. Lease Offer - The server sends the above information and marks the
offered address as unavailable. The message sent is a DHCPOFFER
broadcast message.
3. Lease Acceptance - The first offer received by the client is
accepted. The acceptance is sent from the client as a broadcast
(DHCPREQUEST message) including the IP address of the DNS server
that sent the accepted offer. Other DHCP servers retract their
offers and mark the offered address as available and the accepted
address as unavailable.
4. Server lease acknowledgement - The server sends a DHCPACK or a
DHCPNACK if an unavailable address was requested.
All DHCP packets travel as UDP datagrams; all client-sent packets have
source port 68 and destination port 67; all server-sent packets have
source port 67 and destination port 68. For example, a server-side
firewall should allow the following types of packets:
* Incoming packets from 0.0.0.0 or dhcp-pool to dhcp-ip
* Incoming packets from any address to 255.255.255.255
* Outgoing packets from dhcp-ip to dhcp-pool or 255.255.255.255
where dhcp-ip represents any address configured on a DHCP server host
and dhcp-pool stands for the pool from which a DHCP server assigns
addresses to clients
Jim
Kevin Keane wrote:
Christian, actually, your question prompted me to try it again. Turned
out that it was the firewall software on my Nagios box that blocked the
DHCP request. As soon as I turned it off, check_dhcp worked. I'm not yet
sure which ports to open to make it work with the firewall on. So far, I
tried ports 67 and 68 for both TCP and UDP, but that seems not to be enough.
Christian Iñiguez wrote:
Exactly Kevin, you are right
----- Mensaje original ----
De: Kevin Keane <subscript...@kkeane.com>
CC: nagios-users@lists.sourceforge.net
Enviado: jueves, 15 de enero, 2009 13:39:47
Asunto: Re: [Nagios-users] check_dhcp seems not working
jmose...@corp.xanadoo.com wrote:
Christian Iñiguez <challenger_jos...@yahoo.com.mx> wrote:
Hi Everyone
I have a linux server as dhcp server and it's working very well, and I'd
like to monitoring it with nrpe plugin and check_dhcp.>
The problem here is the outcome of check_dhcp is always: CRITICAL: No
DHCPOFFERs were received. But the server is working alright.
The command line is: check_dhcp -s serverip -t 30
What am I doing wrong? Any suggest?
Thanks in advance!
I have no idea which flavor of DHCP you are running (probably ISC's), but I
don't think you are going to be able to run check_dhcp from the DHCP server
itself. The DHCP server will see an incoming requeset from itself and
probably block it. Therefore, using the nrpe method of doing these checks
is a moot point.
If your Nagios server is on the same network as the DHCP server, just run
check_dhcp from the Nagios box. If you're running Nagios on a different
network than the DHCP server and there is a firewall in between, you'll
probably have to do several things:
1. Open up a hole in the firewall to allow the Nagios server to request a
DHCP address from the DHCP server
2. Have a DHCP relay statement on the router's interface your Nagios server
connects to so it knows to which server to relay the DHCP request to
3. Setup a small DHCP subnet on the DHCP server in the same IP range as the
Nagios server so it can offer a valid IP address
I actually have the same problem as Christian, and it does NOT work even
though Nagios is running on a different box on the same network as the
DHCP server. In fact, the Nagios box actually gets its IP address from
the same DHCP server that I would like to monitor (ISC DHCP server 3.0.6
on a SuSE 10.3). I've seen the same problem before against a Windows
DHCP server, too, never been able to make check_dhcp work.
check_dhcp -v prints this:
DHCP socket: 3
Hardware address: 00:0c:29:0e:28:4f
DHCPDISCOVER to 255.255.255.255 port 67
DHCPDISCOVER XID: 2138668641 (0x7F797E61)
DHCDISCOVER ciaddr: 0.0.0.0
DHCDISCOVER yiaddr: 0.0.0.0
DHCDISCOVER siaddr: 0.0.0.0
DHCDISCOVER giaddr: 0.0.0.0
send_dhcp_packet result: 548
No (more) data received (nfound: 0)
Result=ERROR
Total responses seen on the wire: 0
Valid responses for this machine: 0
CRITICAL: No DHCPOFFERs were received.
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