Cable Modems

[Peter R. Wood (Lists)]

>
> hey, an integrated webserver in a cable modem sounds pretty neat!
>
> ...but i'm entirely puzzled about how it would work.  it's obious enough
> in the case of cable/dsl router/firewall products where rfc1918 address
> space is in use, but how would this thing possibly intercept web traffic
> destined to the default router's mac address and rfc1918 ip addresses?
>
> could it be analyzing every packet at wirespeed?  amazing for a consumer
> grade product.
>
> anyone?

I'm not sure of the technical details, but I do know that it works. Below is
a sample from my cable modem's logfile, starting at the bottom with
'BOOTING' (which is when I switch the modem on) to 'Bridge Forwarding
Enabled' (which is when everything has finished).

Time       Priority     Code                              Message
020209063855 7-Information F502.1                   Bridge Forwarding
Enabled.
020209063855 7-Information F502.3                    Bridge Learning
Enabled.
020209063855 7-Information B518.0                  Baseline Privacy is
skipped
020209063855 7-Information I500.0                     Registration Completed
020209063855 7-Information  I0.0                  REG-RSP Registration
Response
020209063855 7-Information  I0.0                   REG-REQ Registration
Request
020209063855 7-Information D509.0       Retrieved TFTP Config
/DOCSIS/1500x300st-1 SUCCESS
020209063855 7-Information D507.0                 Retrieved Time.......
SUCCESS
************ 7-Information D511.0                Retrieved DHCP ..........
SUCCESS
************   5-Warning   D520.2      DHCP Attempt# 1 BkOff: 4s Tot DSC:1
OFF:1 REQ:1 ACK:1
************ 7-Information  D0.0        DHCP CM Net Configuration download
and Time of Day
************ 7-Information T500.0              Acquired Upstream ..........
SUCCESS
************    8-Debug    T503.1     Acquire US with status OK, powerLevel
43, tempSid 3733
************    8-Debug    T505.0                Acquired Upstream with
status OK
************ 7-Information T501.0       Acquired Downstream (693000000
Hz)........ SUCCESS
************    8-Debug    T509.0     Acquired DS with status OK, DS Freq
693000000, US Id 3
************ 7-Information I510.0           *** BOOTING ***
SB4100-4.0.9-SCM07-NOSHELL

Interesting to note the "Retrieved TFTP Config /DOCSIS/1500x300st-1
SUCCESS" - this is the modem's config file which is downloaded from ATT
every time the modem boots. As you can see from the file name, it's set up
for 1500x300 download/upload speeds, which is typically what I get.

Also, here is the information on my cable modem's signal:

Downstream Value
Frequency 693000000 Hz Locked
Signal to Noise Ratio 31 dB
QAM 64
Network Access Control Object ON
Power Level -15 dBmV

Upstream             Value
Channel ID             3
Frequency      38000055 Hz Ranged
Ranging Service ID        3733
Symbol Rate        1.280 Msym/s
Power Level          43 dBmV