I use munin to monitor my system. Here's a munin plugin to monitor the connection stats of the Comcast business class SMC 8014 cable mode/router

This isn't a munin plugin writing guide. I use this one, there are plenty out there.

Anyway, this should be the live link to my cable modem line stats munin daily stats graphic:

You're seeing the frequency in Mhz up/down, power up/down and SNR down numbers. The frequency numbers tend to dwarf everything else so I scaled them down.

Here's the script

#!/bin/sh

case $1 in
   config)
        cat <<'EOM'
graph_title cable modem line stats
graph_args --base 1000 -l 0 -u 100 --rigid
graph_vlabel values up (-u) / down (-d)
graph_category network
graph_info This graph shows the cable modem line stats (down freq scaled 10x)
freu.label fre-u
freu.info Upstream Frequency Mhz
powu.label pow-u
powu.info Upstream Power dBmV
fred.label fre-d/10
fred.info Downstream Frequency Mhz
powd.label pow-d
powd.info Downstream Power dBmV
snrd.label snr-d
snrd.info SNR
freu.cdef freu,1000000,/
fred.cdef fred,10000000,/
EOM
        exit 0;;
esac

curl -s -d "user=user&pws=pass" -c /tmp/ccc.txt "http://10.1.10.1/goform/login" > /dev/null
curl -s  -b /tmp/ccc.txt "http://10.1.10.1/user/feat-gateway-modem.asp" | grep \<td\> | sed -n -e '8s/^<td>/fr
ed.value /' -e '8s/ Hz<\/td>//' -e '12s/^<td>/powd.value /' -e '12s/ dBmV<\/td>//' -e '13s/^<td>/snrd.value /'
 -e '13s/ dB<\/td>//'  -e '14s/^<td>/freu.value /' -e '14s/ Hz<\/td>//' -e '18s/^<td>/powu.value /' -e '18s/ d
BmV<\/td>//'  -e '8p' -e '12,14p' -e '18p'

The only thing you'll need to change is the user/pass values, and the URL for the modem.

Enjoy!