[opennms-discuss] DHCP monitoring questions

[Miller-2, David (Dynacs)]

I have been looking for some info on monitoring DHCP using OpenNMS (didn't
see anything in the faq or docs), but have been running into a little
trouble with it. To the best of my knowledge the following items need to be
configured for monitoring DHCP:

a) OpenNMS must be configured for DHCP monitoring of appropriate
servers (also, OpenNMS should not actually be using a DHCP acquired address
for its address)
b) The DHCP servers must be set up with scope and policy to dole out
addresses on the subnet where the OpenNMS server exists
c) If they (the OpenNMS server and the DHCP servers) are on
different subnets, then IP helper addresses must be configured in the router
where OpenNMS is attached to allow the BOOTP messages to get passed to the
DHCP servers.

The capsd.log currently is showing that Discover request for DHCP fails and
it thinks DHCP is not supported for one of my active DHCP servers, thus it
does not add it to the poller. Any ideas what may be missing or
misconfigured for the Discover to fail?

I also have a few additional DHCP related questions:
1. Any details on what the DHCP monitor actually does? (e.g., does
it attempt to discover DHCP service only, does it actually obtain an IP
address, or is it checking how many addresses are available to be
distributed)
2. How long are addresses held by OpenNMS... does it release
addresses immediately after a successful acquisition of an address ?
3. Can a single OpenNMS poller monitor many DHCP servers (i.e., can
it direct its address request to specific servers) ?

Thanks,
Dave

[Bill Ayres]

Dave,

Here's how I handled this situation. Set up a DHCP relay on the subnet
where opennms resides and configure its helper address to forward
requests to your DHCP server which is on a different subnet. Then
instead of monitoring the actual DHCP server, just monitor DHCP service
on the relay instead. You need to set the correct MAC address of your
opennms host in dhcpd-configuration.xml, and be sure your DHCP server
is configured to send a valid response to a request coming from your
opennms host.

--Bill--

Post by Miller-2, David (Dynacs)
I have been looking for some info on monitoring DHCP using OpenNMS (didn't
see anything in the faq or docs), but have been running into a little
trouble with it. To the best of my knowledge the following items need to be
a) OpenNMS must be configured for DHCP monitoring of appropriate
servers (also, OpenNMS should not actually be using a DHCP acquired address
for its address)
b) The DHCP servers must be set up with scope and policy to dole out
addresses on the subnet where the OpenNMS server exists
c) If they (the OpenNMS server and the DHCP servers) are on
different subnets, then IP helper addresses must be configured in the router
where OpenNMS is attached to allow the BOOTP messages to get passed to the
DHCP servers.
The capsd.log currently is showing that Discover request for DHCP fails and
it thinks DHCP is not supported for one of my active DHCP servers, thus it
does not add it to the poller. Any ideas what may be missing or
misconfigured for the Discover to fail?
1. Any details on what the DHCP monitor actually does? (e.g., does
it attempt to discover DHCP service only, does it actually obtain an IP
address, or is it checking how many addresses are available to be
distributed)
2. How long are addresses held by OpenNMS... does it release
addresses immediately after a successful acquisition of an address ?
3. Can a single OpenNMS poller monitor many DHCP servers (i.e., can
it direct its address request to specific servers) ?
Thanks,
Dave
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