Information Technology Reference
In-Depth Information
.Jul 2 17:16:46.426: //-1/77671F238035/DPM/dpMatchPeersCore:
Result=Success(0) after DP_MATCH_DEST
.Jul 2 17:16:46.426: //-1/77671F238035/DPM/dpMatchPeersMoreArg:
Result=SUCCESS(0)
List of Matched Outgoing Dial-peer(s):
1: Dial-peer Tag=1101
Notice the highlighted output from the
debug
command in Example 6-9. This shows the
router performing digit-by-digit call processing. As the attached phone dials each digit,
the router processes that digit and attempts to find a match from among its dial peer con-
figuration. For the first three dialed digits, the result is clear: more digits needed. After the
caller dials the fourth digit, the router matches dial-peer tag 1101 and processes the call.
Now, we can turn our attention to the POTS dial peer configuration on ROUTER_B,
which has a T1 PRI connection to a PBX system hosting 2XXX extensions (four-digit ex-
tensions beginning with the number 2). In the earlier section, “Configuring Digital Voice
Ports,” the physical characteristics of the T1 VWIC interface were configured to support
T1 PRI connectivity (by using the
pri-group
command). When that command was en-
tered, the router automatically created the voice port 1/0:23, which represented the signal-
ing channel of the T1 PRI connection. Example 6-10 now configures the router to use this
T1 PRI port anytime it receives a call for a 2XXX extension.
Example 6-10
Configuring a POTS Dial Peer for a T1 Interface
ROUTER_B(config)#
dial-peer voice 2000 pots
ROUTER_B(config-dial-peer)#
destination-pattern 2...
ROUTER_B(config-dial-peer)#
no digit-strip
ROUTER_B(config-dial-peer)#
port 1/0:23
It's that simple. Notice that you can use the “.” wildcard to represent any dialed digit. This
instructs the router to send all 2XXX extensions out port 1/0:23 (the T1 PRI interface).
One additional command in this example brings up a big point of discussion:
no digit-
strip
. This command prevents the router from automatically stripping dialed digits from
this dial peer. Now, why would the router do that? Because of the POTS dial peer rule
Cisco programmed into Cisco IOS. Here's the rule:
Digit-Stripping Rule of POTS Dial Peers:
The router automatically strips any explicitly defined digit from a POTS dial
peer before forwarding the call.
Key
To p i c
An explicitly defined digit is any non-wildcard digit. In the case of Example 6-10, 2 is an
explicitly defined digit. This rule is in place primarily to assist with stripping outside dial-
ing codes before sending calls to the PSTN. For example, organizations commonly require
users to dial 9 to access an outside line (often receiving a second dial tone after they have
dialed 9). However, if you keep this access digit prepended to the dialed phone number,
the PSTN carrier rejects the call. Therefore, if you create a POTS dial peer with the
