Information Technology Reference
In-Depth Information
The following line of
debug
dialer events output for an IP packet lists the name of the DDR interface
and the source and destination addresses of the packet:
Dialing cause: Async1: ip (s=172.16.1.111 d=172.16.2.22)
If this does not occur, the most common reason is improper configuration, either of the interesting traffic
definitions, the state of the dialer interface, or the routing (Table 17-6).
Table17-6
Traffic Does Not Initiate a Dial Attempt
Possible Causes
Suggested Actions
Missing or
incorrect
“interesting
traffic”
definitions
Using the command
show running-config
, ensure that the
interface is configured with a dialer group and that there is a
global level dialer list configured with a matching number.
1.
Ensure that the
dialer-list
command is configured to permit
either an entire protocol or to permit traffic matching an
access list.
2.
Verify that the access list declares packets going across the
link to be interesting. One useful test is to use the privileged
exec command
debug ip packet [list number]
using the
number of the pertinent access list, and then attempt to
ping
or otherwise send traffic across the link. If the interesting
traffic filters have been properly defined, you will see the
packets in the
debug
output. If there is no
debug
output from
this test, then the access list is not matching the packets.
3.
Interface state
Using the command
show interfaces [
interface name
]
, ensure
that the interface is in the state “up/up (spoofing).”
Interface in
“standby” mode
Another (primary) interface on the router has been configured to
use the dialer interface as a backup interface. Furthermore, the
primary interface is not in a state of “down/down,” which is
required to bring the dialer interface out of standby mode. Also, a
backup delay
must be configured on the primary interface, or the
backup interface
command will never be enforced.
To check that the dialer interface will change from standby to
up/up (spoofing), it is usually necessary to pull the cable from the
primary interface. Simply shutting down the primary interface
with the configuration command
shutdown
will not put the
primary interface into down/down, but instead will put it into
administratively down, which is not the same thing.
In addition, if the primary connection is via Frame Relay, the
Frame Relay configuration must be done on a point-to-point serial
subinterface, and the telco must be passing the “active” bit, a
practice also known as “end-to-end LMI.”
