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Dial Plan Considerations and Configuration?

Dial plans intelligently route your phone calls. For instance, you don't want to send local calls to your long distance circuit. If you do this you can expect to rack up long distance charges for a local call. A dial plan describes the number and pattern of digits that a user dials to reach a particular telephone number. Access codes, area codes, specialized codes, and combinations of the number of digits dialed are all part of a dial plan.

The Dial Peer

Dial plans are manually defined using dial peers. They are configured to identify where calls originate and terminate and what path the calls take through the network. Configurations in the dial peer determine which dialed digits the router collects and forwards to the destinations. There are 4 call legs associated with every call. They are show below:

Dial peer configurations include codec, Quality of Service (QoS), voice activity detection (VAD), and fax rate. To complete a voice call, you must configure a dial peer for each of the four call legs in the call connection. Dial peers are used for both inbound and outbound call legs. An inbound call leg is when an incoming call comes into the router. An outbound call leg is when an outgoing call is placed out of the router. If the inbound or outbound call legs do not match a pre-defined dial-peer, it will match dial-peer 0 and will be given the default configuration associated with that dial-peer. Below is a sample dial peer configuration for pots and VoIP:

dial-peer voice 1 pots
 destination-pattern 555....
 port 1/0:1

dial-peer voice 2 VoIP
 destination-pattern 555....
 session target ipv4:

Dial peer matching depends on what parameters are included in the configuration. In the above configuration the dial peer will match a call leg based on the destination-pattern. Wildcards for destination patterns are listed below in the chart. For inbound calls it matches on the calling number or ANI. For outgoing legs it matches on the called number or DNIS (dialed number identification service). Another option is to use the incoming called-number command. This command defines the called number destination or DNIS to match on an incoming call leg. Finally, you can use the answer-address command. Use this command to match the calling number of the inbound leg to an inbound dial peer. If two or more dial peers match an incoming or outgoing ANI or DNIS, you can use the preference command to distinguish which one to use. This is commonly done in fail over scenarios when your Subscriber server fails and you want to automatically match the dial peer that points to the Publisher. Preference 0 is the default and is the highest preference.

Wildcards used in destination patterns:

Symbol Description
. Indicates a single-digit placeholder. For example, 555.... matches any dialed string beginning with 555, plus at least four additional digits.
[ ] Indicates a range of digits. A consecutive range is indicated with a hyphen (-); for example, [5-7]. A nonconsecutive range is indicated with a comma (,); for example, [5,8]. Hyphens and commas can be used in combination; for example, [5-7,9].
Note Only single-digit ranges are supported. For example, [98-102] is invalid.
( ) Indicates a pattern; for example, 408(555). It is used in conjunction with the symbol ?, %, or +.
? Indicates that the preceding digit occurred zero or one time. Enter ctrl-v before entering ? from your keyboard.
% Indicates that the preceding digit occurred zero or more times. This functions the same as the "*" used in regular expression.
+ Indicates that the preceding digit occurred one or more times.
T Indicates the interdigit timeout. The router pauses to collect additional dialed digits.

The voice port

Voice ports on routers and gateways physically connect to telephony devices such as telephones, fax machines, PBXs, and PSTN central office (CO) switches. These devices may use several types of signaling interfaces to generate information about on-hook status, ringing, and line seizure. The voice ports at each end of the call need to agree on the type of signaling to be used or there could be an issue with call completion or degraded voice quality. Compared to a dial-peer, the voice port contains the physical parameters while the dial-peer contains the logical parameters. Below is a sample voice port configuration along with an explanation of each parameter:

router(config)# voice-port slot/port Enters voice-port configuration mode. The voice-port configuration commands are nested so that all subsequent commands affect only the specified voice port.
The slot number for analog voice ports on the Cisco MC3810 is always 1. There is no port 0 for voice ports.
router(config-voiceport)# codec {g729r8 | g729ar8 | g726r32 | g711alaw | g711ulaw} (Optional) Configures the voice-port compression mode. The g729ar8 value is the default and is recommended.
The g729ar8 compression mode supports a maximum of 24 simultaneously active on-net voice calls, while the g729r8 value supports a maximum of 12.
The g729r8 and g729ar8 compression modes have a nominal data rate of 8 kbps. The g726r32 compression mode has a nominal data rate of 32 kbps. The g711alaw and g711ulaw compression modes have a nominal data rate of 64 kbps.
router(config-voiceport)# connection {tie-line | plar | plar-opx} string Configures the voice-port connection mode type. If the connection is a PBX, use the tie-line option. If the connection is a Private Line Auto Ringdown (PLAR), use the plar option.
If the PLAR connection is Off-Premises extension (OPX), use the plar-opx option. By using this option, the local voice port provides a local response before the remote voice port receives an answer. For this option, FXO interfaces will not answer until the remote side answers.
Note After a transparent Common Channel Signaling (CCS) connection is configured by entering the connection plar command, any change to the configuration will not take place until the connection is shut down and restarted with a shutdown command and a no shutdown command. For example, the phone number in the plar command can be changed while the connection is in no shutdown state, but the change will not cause the current connection to be closed and a new connection opened to the new phone number. This will only take effect on the next no shutdown command after a shutdown command.

Route patterns

A route pattern is defined as a string of digits and a set of associated digit manipulations that can be assigned to a route list or a gateway. A route pattern is created on the Call Manager via the administration pages. The configuration area can be found by going to route plan>route pattern. Route patterns are similar to dial-peers on an H323 gateway. They provide a means for directing calls to specific gateways. They tie in with route lists and route groups so that redundant gateways can be set up in the event a channel is not available. When creating route patterns there are several wildcard symbols that can be used to encompass a wide range of numbers. Some of the common wildcard characters are listed below.

Character Description Examples
@ The at symbol (@) wildcard matches all NANP numbers.
Only one @ wildcard is allowed in each route pattern.
The route pattern 9.@ routes or blocks all numbers recognized by the NANP.
The following route patterns are examples of NANP numbers encompassed by the @ wildcard.
X The X wildcard matches any single digit in the range 0 through 9. The route pattern 9XXX routes or blocks all numbers in the range 9000 through 9999.
! The exclamation point (!) wildcard matches one or more digits in the range 0 through 9. The route pattern 91! routes or blocks all numbers in the range 910 through 91999999999999999999999.
? The question mark (?) wildcard matches zero or more occurrences of the preceding digit or wildcard value. The route pattern 91X? routes or blocks all numbers in the range 91 through 91999999999999999999999.
+ The plus sign (+) wildcard matches one or more occurrences of the preceding digit or wildcard value. The route pattern 91X+ routes or blocks all numbers in the range 9100 through 91999999999999999999999.
[ ] The square bracket ([ ]) characters are used to enclose a range of values. The route pattern 813510[012345] routes or blocks all numbers in the range 8135100 through 8135105.
- The hyphen (-) character is used, with the square brackets, to denote a range of values. The route pattern 813510[0-5] routes or blocks all numbers in the range 8135100 through 8135105.
^ The circumflex (^) character is used, with the square brackets, to negate a range of values. It must be the first character following the opening bracket ([).
Only one ^ character is allowed in each route pattern.
The route pattern 813510[^1-5] routes or blocks all numbers in the range 8135106 through 8135109.
. The dot (.) character is used as a delimiter to separate the Cisco Call Manager access code from the directory number.
This special character can be used, with the discard digits instructions, to strip off the Cisco Call Manager access code before sending the number to an adjacent system.
Only one . character is allowed in each route pattern.
The route pattern 9.@ identifies the initial 9 as the Cisco Call Manager access code in an NANP call.
* The asterisk (*) character is available as an extra digit for special dialed numbers. The route pattern *411 can be configured to provide access to the internal operator for directory assistance.
# The octothorpe (#) character is generally used to identify the end of the dialing sequence. The route pattern 901181910555# routes or blocks an international number dialed from within the NANP. The # character after the last 5 identifies this as the last digit in the sequence.

Route lists

Route lists contain a list of route groups that are available to send a call to. The route list for a router pattern is selected on the route-pattern configuration page. You configure route patterns from Route Plan>Route List. You add route groups to route lists. Once a route group is added you can manipulate items like the calling party transformation mask, prefix digits outgoing, dial plan type, discard digits and called party transformation mask.

Route groups

The order of configuration in dial plans is as follows. First configure the route group. Then configure the router list. Finally, associate the route pattern to the route list. A route group is an ordered list of gateways for sending calls to. The route group configuration can be found on the Call Manager configuration page at Route Plan>Route group. When configuring a new route group you have the option of adding gateways. You can also select the order to use the gateways. For instance, you might want to use a gateway that provides PRI PSTN access before you use a gateway that only has 2 FXO ports. Each gateway, or all ports or selected ports combination, can only belong to one route group and can only be listed once within that route group. A route group can be part of multiple route lists. In the following diagram a number is dialed. The number matches a pre-configured dial-pattern in Call Manager. The route-pattern has a route-list configured. The route-list contains one or more ordered route-groups. Each route-group has an ordered list of gateways. The logic flows through each route-group and each gateway until an open channel is found. Once an open channel is found the call will be routed.

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