Cable modem activity even when computer off

I was looking forward to the increase in download speed
that RCN promised to all its Internet customers in a Feb.
letter. Along with the speed increase, though, has come
something strange: the modem's data light is now continuously
flickering, as if I'm connected to a streaming audio or video
Web site, even when the computer is turned off. The obvious
first troubleshooting response -- recycling the modem
power -- has no effect. Only disconnecting the modem from
the computer or unplugging the computer from the power
outlet stops the activity. This means that the activity
must be driven from somewhere out on the Internet, right?
Is there any easy way to find out where it's coming from?

--
Charles Packer
http://cpacker.org/whatnews
mailboxATcpacker.org

On 5.3.11 6:19 , Charles Packer wrote:
> I was looking forward to the increase in download speed
> that RCN promised to all its Internet customers in a Feb.
> letter. Along with the speed increase, though, has come
> something strange: the modem's data light is now continuously
> flickering, as if I'm connected to a streaming audio or video
> Web site, even when the computer is turned off. The obvious
> first troubleshooting response -- recycling the modem
> power -- has no effect. Only disconnecting the modem from
> the computer or unplugging the computer from the power
> outlet stops the activity. This means that the activity
> must be driven from somewhere out on the Internet, right?
> Is there any easy way to find out where it's coming from?
>
> --
> Charles Packer
> http://cpacker.org/whatnews
> mailboxATcpacker.org


Start with tcpdump or Wireshark to capture what is
in the incoming interface. It is not completely
sure if the traffic comes as far, as it is there
when the Ethernet link is up, but the computer
is down.

It may be the modem discussing with its network
control as soon as the link is up.

--

Tauno Voipio
tauno voipio (at) iki fi

On Fri, 04 Mar 2011 20:19:08 -0800, Charles Packer rearranged some
electrons to say:

> I was looking forward to the increase in download speed that RCN
> promised to all its Internet customers in a Feb. letter. Along with the
> speed increase, though, has come something strange: the modem's data
> light is now continuously flickering, as if I'm connected to a streaming
> audio or video Web site, even when the computer is turned off. The
> obvious first troubleshooting response -- recycling the modem power --
> has no effect. Only disconnecting the modem from the computer or
> unplugging the computer from the power outlet stops the activity. This
> means that the activity must be driven from somewhere out on the
> Internet, right? Is there any easy way to find out where it's coming
> from?

It's coming from all the other users (your neighbors) that are sharing
the cable connection. You didn't think they ran a cable JUST to your
house, did you?

On 03/04/2011 10:19 PM, Charles Packer wrote:
> I was looking forward to the increase in download speed
> that RCN promised to all its Internet customers in a Feb.
> letter. Along with the speed increase, though, has come
> something strange: the modem's data light is now continuously
> flickering, as if I'm connected to a streaming audio or video
> Web site, even when the computer is turned off. The obvious
> first troubleshooting response -- recycling the modem
> power -- has no effect. Only disconnecting the modem from
> the computer or unplugging the computer from the power
> outlet stops the activity. This means that the activity
> must be driven from somewhere out on the Internet, right?
> Is there any easy way to find out where it's coming from?

Looks like your modem just got a firmware change to support your
increased speed, and now you're seeing the background ARP and
broadcast DHCP packets that are a normal part of IPv4 networking
on a shared medium. Whether or not the modem flashes the data
light for those packets is a function of the modem's firmware.
Some do, some don't. Standard advice for those who don't like to
see that light flashing is, "Put a piece of black tape over it."

--
Bob Nichols AT comcast.net I am "RNichols42"

On Mar 5, 10:21 am, Robert Nichols
<SEE_SIGNAT...@localhost.localdomain.invalid> wrote:
> Looks like your modem just got a firmware change to support your
> increased speed, and now you're seeing the background ARP and
> broadcast DHCP packets that are a normal part of IPv4 networking
> on a shared medium. Whether or not the modem flashes the data
> light for those packets is a function of the modem's firmware.
> Some do, some don't. Standard advice for those who don't like to
> see that light flashing is, "Put a piece of black tape over it."

Okay...I can live with the blinking if I know what it is. Now the
problem is that RCN increased my upload speed as promised,
but not my download speed, according to the results I'm getting
from using the testing tool at bandwidthplace.com. What RCN
desk should I call: technical or accounts?

--
Charles Packer
http://cpacker.org/whatnews
mailboxATcpacker.org