ISDN CHAP conversion FAQs

What is CHAP?
What does CHAP mean to me?
What will happen if I'm using a password greater than 8 characters?
What will happen if I'm using a Cisco 800 series ISDN router?
What will happen if I’m using a Toshiba ISDN modem?

Q: What is CHAP?

A: CHAP stands for "Challenge Handshake Authentication Protocol". With CHAP, the authenticator (i.e. the server) sends a randomly generated ``challenge'' string to the client, along with its hostname. The client uses the hostname to look up the appropriate secret, combines it with the challenge, and encrypts the string using a one-way hashing function. The result is returned to the server along with the client's hostname. The server now performs the same computation, and acknowledges the client if it arrives at the same result.

CHAP doesn't only require the client to authenticate itself at startup time, but sends challenges at regular intervals to make sure the client hasn't been replaced by an intruder, for instance by just switching phone lines.

Q: What does CHAP mean to me?

A: Qwest Internet Services is making changes to its network to gain efficiencies and expand the Qwest.net footprint. To accommodate this optimization, the Qwest.net authentication process will be changing.

Q: What will happen if I'm using a password greater than 8 characters?

A: When Qwest switches to the new CHAP-first architecture, customers who use passwords greater than 8 characters will not be able to authenticate for Internet Access. To avoid an interruption of service simply follow our instructions on changing your password.

Q: What will happen if I'm using a Cisco 800 series ISDN router?

A: Customers with Cisco 800 series ISDN routers may need to make a configuration change to authenticate using CHAP. The instructions for making that change are as follows:

First make sure you have the ability to access the router. If you can, continue with the steps listed below:

• Scenario 1 - You have full access to your router configuration with the current IOS.
• Scenario 2 - You have full access to your router configuration with an older IOS.
• If you cannot access your router configuration, please contact your IT department or Cisco for help configuring the commands below.

• Go into your dialer interface and type this command --- (remember to hit "Enter" after each command):
  ppp authentication chap callin
• If you cannot browse, type the next two commands and proceed to Scenario 2:
  ppp chap hostname (qwest username)
  ppp chap password (qwest password)
• If you can browse:
  • Save the changes
  • Reboot the router
  • Connect and browse

Scenario 2 - You have full access to your router configuration with an older IOS.

• Go into your dialer interface and type this command --- (remember to hit "Enter" after each command):
  ppp authentication chap callin
• Exit the dialer interface
• Enter the main configuration page and type these two commands:

hostname (qwest user name)
ppp chap password (qwest password)
• Save the changes
• Reboot the router
• Connect and browse

Q: What will happen if I’m using a Toshiba ISDN modem?