Having problem measuring throughput (ntop, iftop, systat, etc.)

Y

Yamil Selman

Hi,

I got a problem here, I installed net/ntop to monitor my network traffic , the problem that I have been having is that ntop(8), iftop(8), systat(1), or whatever tool that I use to monitor the bandwidth reports a wrong measure.

Let me clarify;

I have a FreeBSD 10.2 fresh installation. I set sysctl net.inet.ip.forwarding=1(gateway enable), then I installed net/ntop and net-mgmt/iftop.

So the problem is when I test from inside the router (FreeBSD host) for example:

Code: 
wget http or ftp://ftp.freebsd.org/pub/FreeBSD/releases/amd64/amd64/ISO-IMAGES/10.2/FreeBSD-10.2-RELEASE-amd64-dvd1.iso

Wget reports that I am downloading at 4.0 MegaBytes per second and when I take a look to the iftop(8) really I am downloading at 4.0 MegaBytes.

Now if I test from another machine in the network with the default gateway pointed to the FreeBSD(router)

In that machine I am getting 4.0 MegaBytes of speed but in FreeBSD iftop(8) is telling me that I am downloading at 30 KiloBytes per second only, the same thing with ntop(8).

Just to make a point, the FreeBSD router that I am using only have 1 network card, so that is not the real router, it is pointing to the real router. I just want to redirect the traffic to it for measure purpose.

This is the layout:
  • Client(192.168.1.50) with gw (192.168.1.254)
  • Real Router(192.168.1.1)
  • FreeBSD (acting like a router) (192.168.1.254) with gw (192.168.1.1)
So

Code: 
Client >>>> FreeBSD(router) >>>>> RealRouter >>>>>> INTERNET

So what I think is that there is something related with what the FreeBSD only has 1 NIC card. I hope you can help me

Thanks
 
I am testing connecting the FreeBSD Box connected to a Sonicwall mirror Port(SPAN), to catch all the traffic, and I see everything, but the ntop(8), iftop(8), darkstat(8), etc., does not measure the bandwidth properly, I mean the throughput, I see the traffic but I don't see correctly the amount of bandwidth passing through.

Somebody please! Can help me? I am trying to set up a FreeBSD box with ntop(8), to see all the traffic passing through the Sonicwall for monitoring purpose.

Thank you!
 
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