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580 Chapter 8: WAN Protocols and Design
DDR Legacy Concepts and Configuration
Two ways exist by which to configure DDR. The two styles of DDR configuration are called
DDR legacy and DDR dialer profiles. The main difference between the two is that DDR legacy
associates dial details with a physical interface, but DDR dialer profiles-style configuration
disassociates the dial configuration from a physical interface, allowing a great deal of flexibility.
The concepts behind legacy DDR apply to DDR dialer profiles as well, but DDR legacy is a
little less detailed. Although not overly stated in the course, the DDR coverage in the ICND
class is for DDR legacy.
DDR can be used to cause the router to dial or to receive a dial on asynchronous serial
interfaces, synchronous serial interfaces, and ISDN BRI and PRI interfaces. All examples in
this chapter use ISDN BRI.
The following list identifies the four key concepts behind DDR configuration. The first two
concepts are not actually related to the dial process, but relate to the process of choosing when
to dial and when not to dial. The other two concepts relate to dialing, or signaling. The term
signaling is used in ISDN to describe the processes of call setup and takedown, and it is used
synonymously with the term dialing here. The four key concepts are as follows:
Step 1
Routing packets out of the to-be-dialed interface
Step 2
Determining the subset of these packets that trigger the dialing
process
Table 8-31
ISDN-Related EXEC Commands
Command
Function
show interfaces bri
number[:b-channel]
Includes reference to the access lists enabled on the interface.
show controllers bri number
Shows Layer 1 statistics and status for B and D channels.
show isdn {active | history |
memory
| status | timers}
Shows various ISDN status information.
show interfaces bri
number[[:bchannel] | [first]
[last]] [accounting]
Displays interface information about the D channel or the B
channel(s).
show dialer interface bri
number
Lists DDR parameters on the BRI interface. Shows whether currently
dialed by indicating current status. Also shows previous attempts to
dial and whether they were successful.
debug isdn q921
Lists ISDN Layer 2 messages.
debug isdn q931
Lists ISDN Layer 3 messages (call setup/teardown).
debug dialer {events |
packets}
Lists information when a packet is directed out a dial interface, telling
whether the packet is interesting.
ch08.fm Page 580 Monday, March 20, 2000 5:17 PM