Route Filters

When creating route patterns, you can use the "@" wildcard to represent all the routes defined in the North American Numbering Plan (NANP). Although this is a simple way to provide PSTN access to your internal users, you might be providing far more access than you intend. As shown in Figure 11-1, the NANP includes high-expense patterns such as international dialing access, service numbers (such as 411), and 900 numbers. You can assign route filters to route patterns with the @ route pattern to help reduce the danger that full access to the NANP provides. You can accomplish this reduction by filtering what is included in the @ (or 9.@) route pattern.

Figure 11-1. @ Route Pattern Without Route Filters

When using the 9.@ route pattern, Cisco CallManager recognizes that dialing is complete when the user dials 1 + 10 digits (signifying long-distance dialing) or just dials 10 digits (local area codes without the 1). If the number dialed does not begin with a 1, Cisco CallManager considers it a local area code and assumes that dialing is complete after 10 digits.

In an area where seven digits are dialed for local numbers, Cisco CallManager cannot recognize which office exchange codes (NXXs) to use for routing unless you specifically code them as route patterns.

Note

NXX is the central office (CO) exchange code, which consists of three digits that designate a particular CO or a block of 10,000 subscriber lines. N is any digit between 2 and 9, and X is any digit between 0 and 9.

Generally, telephone company service providers arrange many NXXs in a given area code contiguously where you can use route pattern wildcards to assist in your configuration. Coding these individual route patterns for NXXs can be extremely difficult. You can use a route filter to simplify this procedure.

A route filter called seven-digit dialing is always preconfigured in Cisco CallManager. You should assign this route filter to any 9.@ route pattern in an area that uses seven-digit dialing. This route filter removes all local area codes. If a dialed number does not begin with a 1, then it is a seven-digit number, and Cisco CallManager considers dialing complete after seven digits. This situation requires you to configure local area codes specifically as separate route patterns. Doing so is generally not an issue because the number of area codes in a geographical region is usually small.

Note

Route filters are only used with the @ route pattern and are not necessary if you have configured a robust dial plan (that does not use the @ route pattern).

 

Route Filter Tags

You can design and configure route filters using a number of predefined tags in the Cisco CallManager CCMAdmin web utility. Table 11-1 provides a list of tags available to you when implementing route filters.

Table 11-1. Cisco CallManager Route Filter Tags

Tag Name	Example Pattern	Description
AREA-CODE	1 214 555 1212	The area code in an 11-digit long-distance call
COUNTRY-CODE	011 33 123456#	The country code in an international call
END-OF-DIALING	011 33 123456#	The #, which terminates interdigit timeout for an international call
INTERNATIONAL-ACCESS	01 1 33 123456#	The initial 01 of an international call
INTERNATIONAL-DIRECT-DIAL	01 1 33 123456#	The digit that denotes the direct-dial component of an international call
INTERNATIONAL OPERATOR	01 0	The digit that denotes the operator component of an international call
LOCAL-AREA-CODE	214 555 1212	The area code in a 10-digit local call
LOCAL-DIRECT-DIAL	1 555 1212	The initial 1 that is required for some 7-digit calls
LOCAL-OPERATOR	0 555 1212	The initial 0 that is required for operator-assisted local calls
LONG-DISTANCE-DIRECT-DIAL	1 214 555 1212	The initial 1 that is required for long-distance direct-dialed calls
LONG-DISTANCE-OPERATOR	0 214 555 1212	The initial 0 that is required for operator-assisted long-distance calls
NATIONAL-NUMBER	011 33 123456#	The national number component of an international call
OFFICE-CODE	1 214 555 1212	The office exchange code of a North American call
SATELLITE-SERVICE	011 88141234#	A specific value that is associated with calls to the satellite country code
SERVICE	1 411	A value that provides access to local telephony provider services
SUBSCRIBER	1 214 555 1212	A particular extension that is served by a given exchange
TRANSIT-NETWORK	101 0321 1 214 555 1212	A long-distance carrier code
TRANSIT-NETWORK-ESCAPE	101 0321 1 214 555 1212	The escape sequence that is used for entering a long-distance carrier code

 

Configuring Route Filters

Route filter configuration occurs in two major steps:

Step 1.	Configure route filter with necessary tags and arguments.
Step 2.	Apply the route filter to a route pattern or translation pattern.

Just as with access lists on routers, you can create route filters all day and they will never make any difference until you have applied them. Just like an access list, the sole purpose of a route filter is to match criteria; how you apply the route filter determines if the criteria is permitted or denied.

To configure a route filter, use the Cisco CallManager Administration window:

Step 1.	Choose the Route Plan menu.
Step 2.	Choose Route Filter from the menu bar.
Step 3.	Click the Add a New Route Filter hyperlink.
Step 4.	Choose North American Numbering Plan from the Dial Plan menu.
Step 5.	Enter a name in the Route Filter Name field. The name can consist of up to 50 alphanumeric characters, and can contain any combination of spaces, periods (.), hyphens (-), and underscore characters (_). Each route filter name must be unique to the route plan.

After you have accomplished these initial steps, the Route Filter Clause Configuration window appears, as shown in Figure 11-2.

Figure 11-2. Route Filter Clause Configuration Window

From this point, you can combine your tags with operators to define match conditions. Table 11-2 describes the four operators available when configuring route filters.

Table 11-2. Cisco CallManager Route Filter Operators

Operator	Description
NOT-SELECTED	Do not filter calls based on the dialed digit string associated with this tag.
EXISTS	Filter calls when the dialed digit string associated with this tag is found.
DOES-NOT-EXIST	Filter calls when the dialed digit string associated with this tag is not found.
==	Filter calls when the dialed digit string associated with this tag matches the specified value.

The following are examples of match conditions using route filter tags and operators:

• A route filter that uses the tag AREA-CODE and the operator DOES-NOT-EXIST selects all dialed digit strings that do not include an area code.
• A route filter that uses the tag AREA-CODE, the operator = =, and the entry 515 selects all dialed digit strings that include the 515 area code.
• A route filter that uses the tag AREA-CODE, the operator = =, and the entry 5[2-9]X selects all dialed digit strings that include area codes in the range of 520 through 599.
• A route filter that uses the tag TRANSIT-NETWORK, the operator ==, and the entry 0288, along with the tag TRANSIT-NETWORK-ESCAPE, the operator ==, and the entry 101, selects all dialed digit strings with the carrier access code 1010288.

Applying Route Filters

After you have configured the route filter, you must apply them to a route pattern or translation pattern to define the permit or deny action.

Note

Translation patterns are discussed later in this chapter.

To apply the route filter you have created to a route pattern, perform the following steps:

Step 1.	Choose the Route Plan > Route/Hunt > Route Pattern menu selection.
Step 2.	Choose the Add a New Route Pattern hyperlink.
Step 3.	Define the route pattern as @ (or 9.@) to represent the NANP.
Step 4.	Choose your configured route filter from the Route Filter drop-down list, as shown in Figure 11-3.   Figure 11-3. Applying a Route Filter to a Route Pattern
Step 5.	Choose a PSTN exit gateway or route list.
Step 6.	Select the Route This Pattern radio button to allow the numbers matching the filter to route to the PSTN or select the Block This Pattern radio button to block the numbers matching the filter from reaching the PSTN.

Practical Route Filter Example

To demonstrate route filter configuration, imagine that a company wanted to create a route filter that kept 1-900 numbers from being made available in the CallManager route plan. The first step would be to create a route filter that matched the area code 900, as shown in Figure 11-4.

Figure 11-4. Route Filter Matching the 900 Area Code

After the route filter has been added to the configuration, you then need to apply it to a route pattern to define the action required. Figure 11-5 illustrates the creation of a 9.@ route pattern (representing the NANP) with the Match 900 Numbers route filter applied. The key action rests in the Route This Pattern or Block This Pattern radio buttons. If you select to Route This Pattern, you would add only 900 numbers to the Cisco CallManager route plan. Unless you had a very strange organization, this is not a desired effect. Rather, you would select the Block This Pattern radio button to block any numbers containing the 900 area code.

Figure 11-5. Route Pattern Configuration

CallManager allows you to configure multiple 9.@ route patterns, provided each has a unique route filter configuration. This provides flexibility when creating your route plan. By combining multiple 9.@ route patterns with unique route filters, you can route (or block) exactly what you want from the CallManager route plan.

Tip

You could also accomplish this same objective by creating a route pattern of 1900XXXXXXX and choosing Block this Pattern under the route pattern configuration.

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