[smokeping-users] Network Latency of DHCP clients

Dan O'Neill dano at northpb.com
Mon Jul 1 15:07:10 CEST 2013

On Mon, Jul 1, 2013 at 2:25 AM, Paul Mansfield <
paul.mansfield+smokeping at grapeshot.co.uk> wrote:

> On 1 July 2013 10:20, puneet bhardwaj <puneetbhrdwj02 at gmail.com> wrote:
> > Yes  I want to measure network latency between my smokeping monitoring
> > server and all clients who have been allocated a DHCP address and also
> the
> I would suggest using cacti and monitor switch ports instead.
While it is certainly possible to measure latency to your clients, DHCP
allocated addresses add some behaviors that are somewhat incompatible with
long-term measurements. DHCP hands out addresses on request. These
addresses have a lease lifetime and the device that requested the address
will be required to renew prior to the expiration of the lease. There is no
guarantee that the device will always receive the same IP address, although
it is very likely. Further problems arise when devices with an allocated
address leave the network - a cell phone on WiFi, for example, will travel
away from the network and therefore the address is no longer active or may
be reassigned to a different device. This will generate graphs with holes,
spikes and all kinds of noisy information.

Assuming you're going to continue down this path, you'll need to find the
dhcpd.leases file on your DHCP server. In a Linux installation, the file is
normally located at /var/lib/dhcp3/dhcpd.leases. You'll then need to write
a script to read this file, extract IP addresses, generate a set of
Smokeping targets in your smokeping configuration file and finally reload
Smokeping. You may also want to remove targets from leases that are no
longer active, or not...

Bandwidth measurement is not a strength of Smokeping. As mentioned by Paul
Mansfield, you will want to use a different solution that can read SNMP
information from your managed switch to retrieve the number of packets
being sent and received.


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