To configure ISDN, you need to understand that there are both simple and complex configurations.
Although you certainly can make more money by understanding the complex configurations, the
simple ones are just as important. In this section, you will look at some benefits and drawbacks of
two ISDN configuration types: PRI and BRI. In this section you will learn about the differences
between the PRI and BRI interface configurations. First, though, you need to understand how the
old and new ways differ.
How to Order ISDN
Okay, we know this is a CCNP Study Guide and you are probably getting ready for the test, but
after you are certified (or certifiable), you are the Cisco expert and should know the process of
attaining as well as configuring the lines. Here’s what you do:
Who Do I Call?
The first step to getting your ISDN service up and running is to contact your local telephone
company (service provider). The telephone numbers and web addresses for ordering ISDN service
are provided at http://www.nationalisdncouncil.com.
What Do I Need to Tell the Telephone Company?
Ordering ISDN can be as easy as requesting basic phone service from the telephone company;
most of the questions that the telephone company will ask you are the same in both
cases. For example, because ISDN was designed to work over the existing wire, which supports
your current telephone service, you will probably not have to specify any unique wiring
changes or additions. However, some specialized capabilities of ISDN will require you
to provide additional information related to your ISDN equipment selection. The best
way to provide this additional information is through an ISDN Ordering Code (IOC), or as
Cisco calls them, the capabilities package ordering codes, which should be identified in
your ISDN equipment documentation. This will give you a set of standardized BRI line
features that simplify the process of configuring an ISDN line that is connected to an NI1
switch. An example is the package R, which provides circuit-switched data on both B channels
(no voice capabilities). Data capabilities include calling number identification. Cisco
recommends this NI1 capability package for Cisco 801 and Cisco 802 routers.
What Does the Phone Company Need to Tell Me?
Most ISDN connections in North America require the use of one or more service profile identifiers
(SPIDs), which we discussed earlier in this chapter. SPIDs are numbers assigned only by
North American telephone service providers. SPIDS identify the ISDN B channels. As stated
earlier, the SPID format is generally an ISDN telephone number with several numbers added to
it, for example, 40855512340101. Depending on the switch type that supports your ISDN BRI
line, your ISDN line could be assigned none, one, or two SPIDs.
And that’s it. The configuration of and use of this information is covered in the context of
this chapter.
Some of you might have grown up in a router world, where you used dialer map statements
to configure a dial session. But the times they are a-changin’, and actually for the better. By
using a dialer profile, the basic configuration for a physical interface is entered under the actual
interface, but the detailed configuration is placed under a virtual dialer interface. This is a really
good feature if you have a PRI that receives and makes calls to and from different locations
(with different subnets).