Overview

  1. Setting the Static IP Address in the Modem
  2. Obtaining the PPPoE Login Credentials from the Modem
  3. Configuring the Replacement Router
  4. Setting the Modem’s Router to Transparent Bridge
  5. Connecting the Replacement Router and Modem

While CenturyLink definitely has sub-par speeds and poor customer service compared to other ISPs, they are a good choice for a home business or serious computing enthusiast for a few reasons:

  • Unlike most ISPs, they do not block consumer accounts on ports 80, 443, 25, etc.  In other words, one can host one’s own servers for websites, email, etc.
  • They offer static IPs for consumer accounts (highly unusual!), and the monthly charge is reasonable (currently $5).
  • While their speeds are low, their prices are reasonable.

Unfortunately the modem + router supplied (ActionTec C1000A) is pretty poor, and while it offers a decent range of features the level of control is not adequate for any serious networking (eg, mapping incoming ports to different local ports).  In order to get the most out of a CenturyLink connection, it’s necessary to use a different router and so the provided unit’s router needs must be re-purposed as a transparent bridge.

While easy enough to do, the process is complicated by the fact that the replacement router also needs to be set up with PPPoE credentials that are not provided by CenturyLink by default, in conjunction with CenturyLink’s terrible website simply failing to redirect or display help or FAQ pages – sadly, this “please wait” redirection page is a not uncommon end point when clicking around on CenturyLink’s website:

CenturyLink Fail

A good alternative resource for information on the ActionTec C1000A can be found on Rachel Bauer’s Setup Router.

Setting the Static IP Address in the Modem

While not strictly necessary, it’s a good idea to first set the ActionTec C1000A to the static IP address for you CenturyLink account in order to test that it’s available using CenturyLink’s supported equipment.

  1. Log in to the ActionTec C1000A through the web GUI (ie, use your browser to navigate to 192.168.0.1, assuming the default settings haven’t been changed).
  2. Click on the round red “button” labelled “Advanced Setup”.
  3. From the left hand navigation menu under “IP Addressing”, select “WAN Settings”.
  4. Ensure that the “ISP Protocol” is set to “PPPoE”.
  5. Ensure that the “IP Addressing Type” is set to “Static IP”
  6. As per the information provided by CenturyLink upon adding the static IP to your account, enter the “Single Static IP’, “Subnet Mask”, “Gateway Address”, “Primary DNS” and “Secondary DNS”.
  7. Click the “Apply” button to save your changes.

Test your static IP by trying to access some kind of service offered on your local network from outside your local network (eg, if you have a webserver try to access your website using the static IP from your mobile device using your cellular network internet connection, or trying to make a remote desktop connection).  Be sure that any service you are trying to access via the static IP is available, either by adding a port forwarding rule in the modem or by virtue of the service’s provider’s IP being in the modem’s DMZ.

Obtaining the PPPoE Login Credentials from the Modem

While the CenturyLink branded ActionTec C1000A does not provide access to the credentials through the web GUI, they *can* be obtained through some minor trickery via a telnet connection to the modem.  While the configuration files have the password encrypted (or b64 encoded), the actual modem service (pppd) requires that the password be in plain text either in the config file or on the command line.  And if it’s specified on the command line, then it will be visible in the process table – a very common security issue, but to the consumer’s benefit in this instance.

First, ensure that telnet is enabled for the modem:

  1. Log in to the ActionTec C1000A through the web GUI (ie, use your browser to navigate to 192.168.0.1, assuming the default settings haven’t been changed).
  2. Click on the round red “button” labelled “Advanced Setup”.
  3. From the left hand navigation menu under “Remote Management”, select “Remote Telnet”.
  4. Enable telnet and set the user name and password.

Then, telnet into the modem and do a little bit of jiggery-pokery to obtain the PPPoE login credentials.  CenturyLink technical support should be able to provide this as well, but their support is not very reliable or easy to work with so obtaining them directly from the modem will likely be both faster and more accurate.

  1. Using the telnet client of your choice, telnet to 192.168.0.1 and log in using the credentials you set up.
  2. Search through the process list with pidstat (full listing of process information) and sh (to get around the basic shell commands being neutered by ActionTec – another security hole):
     sh -c "/usr/bin/pidstat -l -C pppd"
  3. Copy the PPPoE credentials username and password from the output.  Example (with the user ID and password edited out):
    10:02:05          PID    %usr %system  %guest    %CPU   CPU  Command
    10:02:05         1623    0.00    0.01    0.00    0.01     1  pppd -c ppp0.1 -D 0 -i ptm0.0 -u “[user]@qwest.net” -p “[password]” -f 0 -k -P “[password]” -M 1492

Todd Miller reports that his C1000A lacks pidstat altogether.  However, the entire command line entry can still be viewed by examining the process file associated with it ([pid] is the process ID obtained from ps):

$ sh -c "ps | grep pppd"
[pid]
$ sh -c "cat /proc/[pid]/cmdline"
pppd -c ppp0.1 -D 0 -i ptm0.0 -u "[user]@qwest.net" -p "[password]" -f 0 -k -P "[password]" -M 1492

On a side note, there are many more web GUI pages available that are not linked to from the main GUI.  These can be listed for manual access from the telnet command line, but they are likely not supported and may actually screw up your modem’s settings beyond recovery if used.  Nonetheless, for the braver souls here’s how to list the pages available:

cd webs
ls -al

Configuring the Replacement Router

Next up is transferring these settings to the router to be used in place of the ActionTec C1000A.  In this post, the router is assumed to be flashed with DD-WRT in order to generalize the process as much as possible; specifically, the ASUS RT-N66U with DD-WRT version K3.X, build 27360, feature-set ‘big’.

Configure the Static IP Address in the Router

  1. Log in to the replacement router web GUI from any machine connected to it.
  2. Navigate to the “Setup” tab, “Basic Setup” secondary tab, “WAN Setup” section.
  3. Change the connection type to “Static IP”.
  4. Enter the “WAN IP Address”, “Subnet Mask”, “Gateway”, “Static DNS 1” and “Static DNS 2” to match the CenturyLink information from the modem / customer service:CenturyLink WAN Setup Static IP
  5. Click the “Apply Settings” button to save & apply the new settings.

Configure PPPoE in the Router

  1. Log in to the replacement router web GUI from any machine connected to it.
  2. Navigate to the “Setup” tab, “Basic Setup” secondary tab, “WAN Setup” section.
  3. Change the connection type to “PPPoE”.
  4. Enter the PPPoE username and password obtained from the router / customer service.CenturyLink WAN Setup PPPoE

Setting the Modem’s Router to Transparent Bridge Mode

With the replacement router ready to take over for the modem’s built in routing functions, we should first disable the router’s wifi. While not strictly necessary, it won’t work after bridging mode is enabled and so wastes power and may produce interference with the replacement router’s wireless signal:

  1. Log in to the ActionTec C1000A through the web GUI (ie, use your browser to navigate to 192.168.0.1, assuming the default settings haven’t been changed).
  2. Click on the round grey “button” labelled “Wireless Setup”.
  3. From the left hand navigation menu under “Basic Settings”, select “Radio Setup”.
  4. Ensure “Wireless Radio” radio button “Disable” is selected.
  5. Click the “Apply” button to save the changes.

Next, the CenturyLink modem’s router should be set to transparently bridge the connection from the modem to the replacement router:

  1. Log in to the ActionTec C1000A through the web GUI (ie, use your browser to navigate to 192.168.0.1, assuming the default settings haven’t been changed).
  2. Click on the round red “button” labelled “Advanced Setup”.
  3. From the left hand navigation menu under “IP Addressing”, select “WAN Settings”.
  4. For “ISP Protocol”, select “Transparent Bridging”.
  5. Click the “Apply” button to save the changes.

Connecting the Replacement Router and Modem

The modem’s LAN ethernet ports are now functionally equivalent to a switch connected to the CenturyLink network.  Connect the WAN port of the replacement router to any of the modem’s ethernet LAN ports and power cycle the modem and router.  The replacement router should now provide full internet connectivity via the CenturyLink network, with the static IP pointing to it.

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