LAN slow or dead, intermittently

Janos Dohanics web at
Fri Jun 24 15:34:13 UTC 2016

Hello List,

Please help me figure out what makes my LAN intermittently slow or just
about dead.

The LAN consists of a pfSense router (m1n1wall), a Netgear GS724T
switch, a recently installed FreeBSD 10.3 machine, several Windows 7 Pro
machines, androids and iPhones, and a Brother printer, altogether
between a dozen and 2 dozen networked devices. 

There are no local servers on the network, so as far as I can tell,
most traffic to and from the local nodes is with the internet

Desktops have wired connections (100 MB or 1 GB NICs), but the phones
and most laptops are connected by WiFi.

WiFi is provided by a Linksys E1500 configured to work only as a WiFi

There is also a Linksys RE4000W WiFi extender on the network.

The FreeBSD machine, the printer, the switch, the E1500 and RE4000W
WiFis have static IP addresses. Most of the Windows machines have
reserved DHCP addresses, the rest are unreserved DHCP. pfSense is
providing the DHCP server.

I started to investigate the problem using mtr(8) which runs every 10
minutes. Several times in my testing, the average RTT between the
FreeBSD machine ( and the router's LAN interface
( was hundreds of milliseconds. Also, several times, 1 out
of the 10 packets is lost, but whenever this packet loss occurs, RTTs
are mostly 0.1 or 0.2 ms, but always less than 1 ms.

Pinging various hosts on the LAN at times is in the 10s of milliseconds
or higher.

Using my FreeBSD laptop and the FreeBSD machine, I tested the LAN with
netperf(1) which showed over 80 Mbit/s in good times but also less than
1 Mbit/s at other times.

During off-hours, I have disconnected and then reconnected computers
one by one, but could not identify any as the culprit. Replaced the
switch and patch cables - the problem is still there... intermittently.

None of the Windows computers seems to have any malware which might
flood the network. I looked at pftop, and traffic seems to be legit -
but how could I see all LAN traffic and possibly correlate it with the
slowdown? Could this be caused by a broken networking hardware? How
would I identify that?

What is the intelligent way to track down this problem? Please advise.

Janos Dohanics

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