[TriLUG] (~OT) RoadRunner Network Config

[Ben Pitzer]

So basically what happens is that everything, cable modem included, uses
DHCP.  Here are the steps that occur in a DOCSIS cable modem boot:

1. Cable modem is powered on
2. CM ranges for upstream frequency, and locks on with the Cable Modem
Termination System (CMTS) at the cable provider hub site
3. CM ranges for downstream frequency, and locks on with the CMTS at the
cable provider hub site
4. The CM broadcasts a DHCP request, which the CMTS fowards to the
appropriate DHCP IP, as configured in its helper addresses.
5. The DHCP server refers to its database, typically LDAP, and returns the
record for the CM's mac address.  This LDAP record includes the name of the
config file that the CM needs to download
6. Now armed with an IP after DHCP responds (not a 192.168.x.x, typically,
but rather a provider specific subnet assignment on a private subnet), the
CM broadcasts a TFTP request to pull down the config file.  The CMTS fowards
this request along as well, using a configured helper address, to the
correct TFTP server, which provides the CM's requested config file.
7. The CM configures itself with the config file, which specifies (among
other things) the upstream and downstream bandwidth caps for that modem, and
the # of IP addresses that Customer Premise Equipment (CPEs) behind that
modem can get.
8. Each CPE (could be a computer, router, or whatever, anything that is
connected to the CM or cable router's Ethernet backend) is now able to make
a DHCP request for an IP address.
9. The MAC address for the CM is again verified with the LDAP database, and
the IP is provided to the CPE, so long as you aren't trying to exceed the
max # of IPs that your account will provide.  Thus, if you are allowed 3
IPs, then DHCP will allow 3 CPEs to get IPs, but should refuse the 4th.  Or
that might get stopped at the CM.  I can't remember.
10 CPE is now configured with an IP

I'm not sure how much of this has changed since my days at TWC/RR, but
that's how I remember it working at that time.  So basically, that's why
they tell you to reboot your cable modem any time you have a problem, to get
it to reload the config.  Just FYI.

Regards,
Ben Pitzer

On 9/5/07, Craig Taylor <ctalkobt at gmail.com> wrote:
>
> I got it configured - just had to unplug the modem, renew my leases and
> plug
> it back in.
>
> On 9/5/07, John Broome <jbroome at gmail.com> wrote:
> >
> > On 9/5/07, Matt Pusateri <mpusateri at wickedtrails.com> wrote:
> > > I believe the modem actually sits at 192.168.100.1
> >
> > Crap.  that's what i get for trying to use my memory.
> >
> >
> > --
> > There are three R's to windows tech support: "Restart, Reboot,
> Reinstall"
> > --
> > TriLUG mailing list        :
> http://www.trilug.org/mailman/listinfo/trilug
> > TriLUG Organizational FAQ  : http://trilug.org/faq/
> > TriLUG Member Services FAQ : http://members.trilug.org/services_faq/
> >
> --
> TriLUG mailing list        : http://www.trilug.org/mailman/listinfo/trilug
> TriLUG Organizational FAQ  : http://trilug.org/faq/
> TriLUG Member Services FAQ : http://members.trilug.org/services_faq/
>