6.3 Time Based Access Lists
6.3.4 Case study:  time based ISDN
This sample configuration shows an example of time-based DDR applied to ISDN and async (POTS/modem) connections. For ISDN, HTTP traffic is considered uninteresting at all times and any other IP traffic is considered interesting during "open hours" as defined by the time range "only-during-open-hours." For async (POTS/modem) connections, broadcasts are only considered interesting during "open hours" and all other traffic is considered interesting at all times. Again, "open hours" is defined by the user using the time range "only-during-open-hours."

The time policy used in this example starts January 1, 2001, and goes active weekdays between 7:30 a.m. and 6:30 p.m., Saturdays between 8:30 a.m. and 1:30 p.m., and Sundays between 8:30 a.m. and 6:30 p.m. Before January 1, 2001, the time range is inactive all days at all times.

These configurations were captured on a low-end platform; however, the concept can be easily applied to platforms with higher port density. In this particular case, the auxiliary port of the router is used for async (POTS/modem) dialing. The same async configuration can be applied to other access servers whether or not they have internal modems. Not all platforms maintain the correct time after reload. You may need to use Network Time Protocol (NTP) to guarantee that the date and time are correct even after reloading the router.

To implement this configuration, you need the following:

  • The hostname of each side.
  • A password for Challenge Handshake Authentication Protocol (CHAP).
  • The IP addressing scheme (subnets and addresses).
  • Phone numbers to dial.
  • The time policy to be defined and a time range to be applied to the definition of interesting traffic.
  • Cisco IOS® Software Release 12.0T