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Cisco 675 DSL Modem - Single Static IP Configuration

Earthnet Cisco 675 NAT Configuration

This document will assist you in configuring a Cisco 675 DSL router for use with Earthnet's DSL internet access service. You can also follow this tutorial if you need to update your DNS servers addresses.

Part 1 - Connect to your modem's interface

You should receive several items with your DSL router package, including a "management cable". You will need to use this cable in conjunction with your computer to enter the appropriate configuration into your router's non-volatile RAM (NVRAM), so that it can connect to our service with all of the proper settings.

One end of the management cable connects to the computer's serial port and has 9 pins. The other end (which looks similar to a phone connector) connects to the port on the Cisco labeled MGMT.

Once this is connected, you can log in using a program such as HyperTerminal (assuming you are using a Microsoft Windows-based computer), or any other terminal emulation software. The settings on your terminal software should be:

Once you've set up the connection you should be able to hit ENTER a couple of times and see it ask for a password. You've successfully establish a serial connection with the router and can now configure it!

Part 2 - Enter Enable Mode

The Cisco 675 ships with no password by default.

You will know that you're in 'enable mode' by the # sign after the prompt.

To make the necessary changes to your router, begin with the following:

set nvram erase

The router will then reboot.

As you progress through these instructions, whenever it says 'enter enable mode', repeat the paragraph above.

Part 3 - Set a Password for the Router's Configuration Shell

The first thing you want to do after entering your router's configuration mode is to set a password for the router's configuration shell. This will keep malicious people from logging into your router, and enable you to remotely manage the router's configuration in the future.

The password should be something you can remember, but something that is secure.
Secure passwords have a combination of uppercase and lowercase letters, numbers, and at least one special character (like ! or @). Examples of these are:

(Please don't use any of these examples!)

Once you have chosen a password, either make sure it is something you can remember, or write it down in a safe place where only you have access to it.

To change it in the router, type:

set password exec <password>

For example: set password exec Open!d00r

Because a person would have to know the exec password to log into the router at all, it's not necessary to put a password on the enable mode. However, if you elect to do this anyway, the syntax is as follows:

set password enable <password>

If you do not set an enable password, just hit ENTER from now on when it prompts you for a password after typing 'enable'.

Part 4 - Configure the Router

Type the following:

set bridging rfc1483 disabled

This disables bridging mode, which Earthnet does not support (We use PPP instead)

When it reboots, enter enable mode, and continue typing:

set ppp wan0-0 ipcp <your ip address>
set ppp wan0-0 dns
set ppp restart enabled
set ppp wan0-0 authentication enable
set ppp wan0-0 login <loginname>
set ppp wan0-0 password <password>
set int eth0 address
set int eth0 netmask

set dhcp server pool 0 ip
set dhcp server pool 0 netmask
set dhcp server pool 0 size 252
set dhcp server pool 0 dns
set dhcp server pool 0 sdns
set dhcp server pool 0 gateway
set dhcp server pool 0 lease 86400
set dhcp server pool 0 enabled
set dhcp server enabled

set web disabled
set web port 64800
set nat enabled
set dhcp client disabled


At this point your router will reboot and should successfully connect to Earthnet's network using the IP address you specified.

If you watch the WAN link light (the green one), it should blink for a little while, and then go solid. It should stay solid thereafter.

If it goes black or starts blinking, there is a problem, and you should contact Earthnet at 303-546-6362. Usually this is going to be a Century Link problem, but we suggest you call us first so that we can determine that for sure, to prevent any sort of "wild goose chase" with Century Link.

You can test the connection by logging into the router and attempting to ping something. An address outside of the Earthnet network that should usually be up is From your CBOS prompt, type 'ping' and press ENTER. You should see a 'ping reply,' which indicates that your router is configured correctly. If you see 'request timed out,' then it means there are errors, and you should contact our support to troubleshoot it.

At this point, in most cases, you should make sure that your Cisco 675 is plugged into your computer's ethernet card with provided crossover cable, attaching it to the ENET jack on the 675. Alternatively, if you are using an ethernet hub for connectivity, the 675 should either be plugged into the 'crossover' port with the crossover cable, or it should be plugged into a normal port with a normal ethernet cable.

After your Cisco 675 is connected reliably, you should configure your computer to use DHCP for its IP address. The way to do this varies with operating systems - some show it as "obtain an IP address automatically" or "obtain an address from a DHCP server."

Once your computer is set up to get its IP address from DHCP, you may have to reboot it. If so, when it comes back up, it should have requested an IP address from the Cisco 675 and received one (the first one will be, the second, and so on). You can test this by trying to ping from your computer. You should be able to ping your router(, as well as something outside of the router ( is a good one to check your xDSL circuit).

If all of this works correctly, you have successfully set up your DSL connection.

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