Dial-Peers

[shalushar]

• Introduction
• Syntax of a pots dial-peer
• Example
• Matching rules for Outbound dial-peer
• Matching rules for inbound VoIP peers
• Peer ID 0 (PID=0)
• Related Links
• dial peer location

Introduction

This describes concept of dial-peer and steps to debug dial-peer.

Cisco IOS uses two types of dial-peers. They are defined as:-

• Plain old telephone systems (POTS) dial peer—These define the characteristics of a traditional Telephony network connection. The POTS dial peer maps a dial string to a specific voice port on the local router/gateway. Normally, the voice port connects the router/gateway to the local public switched telephone network (PSTN), private automatic branch exchange (PBX), or telephone.

• Voice-Network dial peers—These define the attributes of a packet voice network connection. Voice-Network dial peers map a dial string to a remote network device.

Different technologies used by dial peers are explained here:-

• Voice over IP (VoIP) - The dial peer is mapped to the IP address, Domain Name System (DNS) name, or server-type of the destination VoIP device that terminates the call. This applies to all VoIP protocols such as H.323, SIP, and Media Gateway Control Protocol (MGCP).
• Voice over Frame Relay (VoFR) - The dial peer is mapped to the data-link connection identifier (DLCI) of the interface from which the call exits the router.
• Voice over ATM (VoATM) - The dial peer is mapped to the ATM virtual circuit for the interface from which the call exits the router.
• Multimedia Mail over IP (MMoIP) - The dial peer is mapped to the e-mail address of the Simple Mail Transfer Protocol (SMTP) server. This type of dial peer is used for Store and Forward Fax (on-ramp and off-ramp faxing).

Syntax of a pots dial-peer

dial-peer voice <tag> pots

destination-pattern <number>

port <port #>

<other configurable options>

• tag is a numeric value that has locally significant only.
• destination-pattern <number> - number needed to route a call (valid characters are 0-9, A-D, *, #, . , T).
• port <port#> - voice-port where the call is sent once a destination-pattern is matched.
• <Other configurable options>

application <ivr application>

Note - Pots peers strip the pattern that is match and forwards the rest.

Example

dial-peer voice 123 pots                            dial-peer voice 123 pots

  destination-pattern 2..   ===>                  destination-pattern 2

  port 1/1/0                                               port 1/1/0

  prefix 2                                                  prefix 2

Note:- the above 2 peers are functionally equivalent.

Wild-cards - A dot (.) is used to represent any single digit to be collected ex. 2…. Would match any extension in RTP.

T - used for variable length dialing - Gateway will continue to collect digits until the inter-digit timeout expires - can incorporate a terminating character with:‘dial-peer terminator x’ globally, where x is any DTMF tone.

Matching rules for Outbound dial-peer

For call routing, dial-peers are matched solely on destination-pattern using the following rules:-

1. Most exact longest match.

2. Preference is used as tie breaker.

Note: If variable length dialing is *NOT* used!

Example 1:

dialpeer           destpat               preference             session-target
1                      4085271048             0 (highest)               voip1
2                      408527....                0                             voip2
3                      408527....                1 (lower)                  pots 1 (interface)
4                       ..........                    1                            0:D (interface)
5                       ..........                    0                            voip3

So, if the called number is 4085271048, the order of attempts will be 1,2,3,5,4.

Example 2:

dial-peer            destpat             preference
1                          408527....             0
2                          4085271048          1
3                          4085271...            0

And the number dialed is 4085271048, the order will be 2, 3, 1.

Note that digits matched supercedes precedence.

If variable length dialing is used, then dial-peer matching changes slightly for calls where the DNIS is received one digit at a time (i.e. not PRI):

• The first match is taken regardless of the number of digits explicitly matched if “digit T” is not used.

• Longest match is still followed if all destination-patterns have “digit T”

Example - Variable length dial string

Example 1:

dialpeer              destpat             preference             session-target
1                        4085271048             0                                 voip1
2                        408…                      1                                 voip2
3                        408…                      0                                 voip3

So, if the called number is 4085271048, the  order of attempts will be 3 then 2. and only 408527 will be collected by the router.  Peer 1 will never be

used.  If the call is an inbound ISDN call with called party=4085271048, then peer 1 will be matched.

Example 2:

dialpeer              destpat                 preference             session-target

1                        408527104.T                  1                         voip1
2                        408…T                          0                         voip2

So, if the called number is 4085271048, the  order of attempts will be 1 then 2.

Matching rules for inbound VoIP peers

For peers where the call leg (VoIP) matches the dial-peer type (VoIP):

1. if the type is matched, associate the called number with the ”incoming called-number <string>”

2. else if the type is matched, associate calling-number with

    ”answer-address <string>”

3. else if the type is matched, associate calling-number with

    ”destination-pattern <string>”

4. else match PID=0

Answer-address: config option under a dial-peer that is used to match the ANI of the call to the <string> in the config command.

Incoming called-number: config option under a dial-peer that is used to match the DNIS of the call to the <string> in the config command.

Peer ID 0 (PID=0)

Peer ID 0 is an un-configured dial-peer used for inbound matching only.  The matched inbound peer defaults to PID=0 if no other inbound peer is found based on matching criteria.PID=0 has a default configuration that cannot be changed.

Example for inbound voip peer

Output of “debug voip ccapi inout”:

Example 1 - No voip peers:

*Mar  2 01:19:50.561: cc_api_call_setup_ind (vdbPtr=0x815CAA28, callInfo={called=200, calling=100, fdest=1 peer_tag=0}, callID=0x816AAEC0)

Example 2: - dest-pat only

dial-peer voice 1234 voip

destination-pattern 1..

session target ipv4:10.1.1.1

*Mar  2 01:22:14.089: cc_api_call_setup_ind (vdbPtr=0x815CAA28, callInfo={called=200, calling=100, fdest=1 peer_tag=1234}, callID=0x816AAEC0)

Example 3: - overriding with answer-address

dial-peer voice 1234 voip

destination-pattern 1..

session target ipv4:10.1.1.1

!

dial-peer voice 9876 voip

answer-address 100

*Mar  2 01:28:03.173: cc_api_call_setup_ind (vdbPtr=0x815CAA28, callInfo={called=200, calling=100, fdest=1 peer_tag=9876}, callID=0x816AAEC0)

Example 4: - overriding answer-address with incoming called number

dial-peer voice 1234 voip

destination-pattern 1..

session target ipv4:10.1.1.1

!

dial-peer voice 9876 voip

answer-address 100

!

dial-peer voice 5678 voip

incoming called-number 200

*Mar  2 01:29:11.089: cc_api_call_setup_ind (vdbPtr=0x815CAA28, callInfo={called=200, calling=100, fdest=1 peer_tag=5678}, callID=0x816AAEC0)

PID 0 for inbound voip peers has the following configuration:

•   any codec
•   ip precedence 0
•   vad enabled
•   no rsvp support
•   fax-rate voice

PID 0 for inbound pots peers has the following configuration:

  no ivr application

Related Links

• Understanding dial-peers

• dial peer location

https://supportforums.cisco.com/thread/2188482