The following is taken from Cacti's FAQ page at 
http://www.raxnet.net/products/cacti/documentation.php?action=view&id=8

Before you can create traffic graphs, Cacti must have working SNMP 
support. One way to do this is to compile PHP with SNMP support built 
in, many times you can install the 'php-snmp' package to do this. The 
second option is to have Cacti call the snmpget and snmpwalk binaries 
from your ucd-snmp or net-snmp installation [for the curious I chose to 
install net-snmp]. You can use the about page to determine whether to 
are using "built-in" or "external" SNMP support.

Now that you have working SNMP support, follow these steps.

    1. Click "Polling Hosts" on Cacti's menu.
    2. Click "Add" to add a new polling host.
    3. Type a description, hostname, management IP, and SNMP community. 
Make sure to select "Generic SNMP-enabled Host" under "Host Template" 
and click "Create".
    4. You should see one or more interfaces listed under the "Data 
Query [SNMP - Interface Statistics]" box. Place a check next to each 
interface that you want to graph. Below the box, select type of graph 
that you want to create (bits, bytes, summation, etc).
    5. Click "Save", and "Create" on the following screen to create your 
graphs.


Brian R. Watters wrote:
>  
> Care to share any of your config to make Cati work with M0n0wall?
> 
> Brian
> 
> -----Original Message-----
> From: zealot [mailto:zealot at tradersguild dot net] 
> Sent: Wednesday, February 04, 2004 12:14 PM
> To: m0n0wall at lists dot m0n0 dot ch
> Subject: Re: [m0n0wall] IP Accounting / snmp for signal strength
> 
> Barry Murphy wrote:
> 
>>Seeing as there are many BSD users here, does anyone know of a script to
> 
> grab 'ipfw count's and drop them into mysql. I need to create a php front
> end showing usage per IP per day for the month, so both the user and I can
> keep an eye on traffic usages.
> 
>>Secondly is it possible to get m0n0wall snmp to show the signal strength
> 
> of a connection so I can graph it.
> 
>>Thanks
>>Barry
> 
> 
> Tried Cacti? Read about it's features at
> http://www.raxnet.net/products/cacti/features.php
> 
> I'm currently using it to gather and display data from my firewall and
> router.