Line groups, hunt lists, and hunt pilots work together to provide call-distribution capabilities in Cisco CallManager Administration. Call distribution is the ability of a caller to dial a number and have the call extended in an ordered manner to members of a group. An example of this functionality is a company 800 number to reach a company technical support department.
A line group contains directory numbers (DNs) and designates the order in which DNs are chosen.
A hunt list contains one or more prioritized line groups.
A hunt pilot is a number that is associated with a hunt list. The hunt pilot can be called directly (for example, to a technical support hotline for a company), or can be reached through forwarding (for example, a caller places a direct call to a technical support group member, and if that member is not available, the call is forwarded to the hunt pilot number). Figure 12-1 demonstrates the proper design of the Cisco CallManager call distribution components.
Figure 12-1. Cisco CallManager Call Distribution Components
A line group allows you to designate the distribution mechanism where DNs are chosen.
Line groups contain the following components, shown in Figure 12-2:
- Idle Not serving any call
- Available Serving an active call but able to accept new calls
- Busy Unable to accept any calls
- Distribution Algorithm A method for distributing calls to members.
- Ring No Answer Reversion (RNAR) timeout value A mechanism for determining how to handle calls that go unanswered. The RNAR is a value, in seconds, after which Cisco CallManager will distribute a call to the next available or idle member of this line group or to the next line group if the call is not answered and if the first hunt option, Try Next Member; Then, Try Next Group in Hunt List, is chosen. The RNAR timeout applies at the line-group level to all members.
- Hunt options The ability to roll past members who are busy, not available, or do not answer, continuing until the call is answered or options are exhausted.
Figure 12-2. Line Group Components
Cisco CallManager distributes a call to idle or available members of a line group based on the call-distribution algorithm and on the RNAR setting.
Line groups contain an algorithm that controls how calls that come in on the hunt pilot are distributed to members, as follows:
Figure 12-3. Call-Distribution Algorithms
Hunt options configured in the line group apply to members in one of the three states: no answer, busy, or not available. Not available is a state triggered by the Do Not Disturb (DND) line state, covered later in the chapter. For a given distribution algorithm, the hunt option specifies where CallManager should distribute a call next if a member of a line group is busy, does not answer, or is not available. The Line Group Configuration window provides the following options for each of the three hunt options:
Distributing the call to other line groups can be useful in an environment where you have Tier 1 and Tier 2 tech support. If all the lines in Tier 1 are busy, the call can spill over to the Tier 2 group. In addition, the Tier 2 employees will see the call redirect information so they can answer the call appropriately.
Call Distribution Scenarios: Top-Down Example
Figure 12-4 shows an example of a line group (Line Group 1) with the following setup information:
- RNA Try Next Member; Then, Try Next Group in Hunt List
- Busy Try Next Member; Then, Try Next Group in Hunt List
- Not available Try Next Member; Then, Try Next Group in Hunt List
Figure 12-4. Call Distribution Example
The call flow is as follows:
Hunting and Forwarding
Hunting differs from call forwarding, although both allow calls to be redirected. Hunting allows Cisco CallManager to extend a call to one or more lists of numbers, where each such list can specify a hunting order that is chosen from a configurable set of algorithms. When a call extends to a hunt party from these lists and the party fails to answer or is busy, hunting resumes with the next hunt party. (The next hunt party varies depending on the current hunt algorithm.) Hunting thus ignores the Call Forward No Answer (CFNA) or Call Forward Busy (CFB) settings for the attempted party.
Call forwarding allows detailed control as to how to extend (divert and redirect are equivalent terms for extend) a call when a called party fails to answer or is busy and hunting is not taking place. For example, if the CFNA setting for a line is set to a hunt pilot number, an unanswered call to that line diverts to the hunt pilot number and thus begins a hunt.
Starting with Cisco CallManager Release 4.1, Cisco CallManager offers the ability to redirect a call when hunting fails (that is, when hunting terminates without any hunt party answering, either because the list of hunt numbers exhausts or because the hunt process times out). If used, this final redirection constitutes a Call Forwarding action. Therefore, the Hunt Pilot Configuration window in Cisco CallManager Administration (choose Route Plan > Route/Hunt > Hunt Pilot) includes call forwarding configuration concepts that are similar to those found in the Directory Number Configuration window (Forward No Answer/Forward Busy).
In Cisco CallManager Release 4.0, hunting stops either when one of the hunt parties answers the call or when the hunt list is exhausted. When hunting stops due to exhaustion, the caller receives a reorder tone (or an equivalent announcement).
Part I: Cisco CallManager Fundamentals
Introduction to Cisco Unified Communications and Cisco Unified CallManager
Cisco Unified CallManager Clustering and Deployment Options
Cisco Unified CallManager Installation and Upgrades
Part II: IPT Devices and Users
Cisco IP Phones and Other User Devices
Configuring Cisco Unified CallManager to Support IP Phones
Cisco IP Telephony Users
Cisco Bulk Administration Tool
Part III: IPT Network Integration and Route Plan
Cisco Catalyst Switches
Configuring Cisco Gateways and Trunks
Cisco Unified CallManager Route Plan Basics
Cisco Unified CallManager Advanced Route Plans
Configuring Hunt Groups and Call Coverage
Implementing Telephony Call Restrictions and Control
Implementing Multiple-Site Deployments
Part IV: VoIP Features
Configuring User Features, Part 1
Configuring User Features, Part 2
Configuring Cisco Unified CallManager Attendant Console
Configuring Cisco IP Manager Assistant
Part V: IPT Security
Securing the Windows Operating System
Securing Cisco Unified CallManager Administration
Preventing Toll Fraud
Hardening the IP Phone
Understanding Cryptographic Fundamentals
Understanding the Public Key Infrastructure
Understanding Cisco IP Telephony Authentication and Encryption Fundamentals
Configuring Cisco IP Telephony Authentication and Encryption
Part VI: IP Video
Introducing IP Video Telephony
Configuring Cisco VT Advantage
Part VII: IPT Management
Introducing Database Tools and Cisco Unified CallManager Serviceability
Configuring Alarms and Traces
Using Additional Management and Monitoring Tools
Part VIII: Appendix
Appendix A. Answers to Review Questions