[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: Baffled by a Cable Modem

Patrick wrote:
Did you try another browser to see if it works with the other sites?

Here's one way to troubleshoot it:

Using FireFox, see if you can get to the cable modem's GUI interface.
Most of them will have one of the following four IPs as their default:

The first thing you should do is make sure your NIC can access all of
those addresses without using a gateway.  As root in a console:

	ifconfig eth0 netmask

This puts your computer on the class B (CIDR /16) network of
and you should be able to hit any of the above four addresses directly
(in fact, any IP from through

Next, try ""; and see if you get the modem's GUI.  If
you don't, try the other three IPs above.  If it's none of those, check
the manual for the modem and see what the default LAN IP is.  Make sure
you get the LAN IP, _NOT_ the WAN IP (anything on the WAN side is the
cable company's side of the connection).

If you can browse the IP, then you know that at least your machine and
your modem can communicate.  Wander through the modem's user interface
looking for its DHCP server settings. Make sure the DHCP server is enabled and take note of which addresses it will offer (usually called
the "pool").

At this point, you should be able to have the modem give you an IP.
Make sure your system is set up to fetch an IP address via DHCP and
either reboot your system, restart NetworkManager (if you use it):

	service NetworkManager restart

or restart the non-NM service:

	service network restart

Once that's all done, again as root in a console, do:

	ifconfig eth0

and verify it has an IP address that's in the range described by the
pool data you got before.  If that's all good, do:

	netstat -rn

and verify that the line that contains the flags "UG" is the same
IP as the cable modem.  Example:    UG  0 0    0 eth0
	          IP of cable modem

If all that checks out, then you SHOULD have a live connection to the
Internet.  The last thing to check is your /etc/resolv.conf file and
ensure that the "nameserver" lines have legitimate IP addresses for
live DNS servers.  This should be set up when the DHCP server gives you
the IP address and default route, but not always.  If it doesn't set
this up, you could manually add entries.  Here's a couple of entries you
can use:


Hope that helps a bit.
- Rick Stevens, Systems Engineer                      ricks nerd com -
- AIM/Skype: therps2        ICQ: 22643734            Yahoo: origrps2 -
-                                                                    -
-         Microsoft Windows:  Proof that P.T. Barnum was right       -

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]