Understanding Dial Peers and Call Legs on Cisco IOS Platforms

Understanding Dial Peers and Call Legs on Cisco IOS Platforms

In Cisco Unified Communications, particularly on IOS (Internetwork Operating System) platforms, dial peers and call legs are essential components for managing voice communications. Let’s delve into what dial peers and call legs are and how they function in a Cisco IOS environment:

Dial Peers:

A dial peer is a concept in Cisco IOS that defines a set of rules and characteristics for matching and routing outgoing or incoming calls. It determines how calls are routed based on certain criteria.

2.Types of Dial Peers:
POTS (Plain Old Telephone Service) Dial Peers: Used for traditional analog and digital voice interfaces.

  • VoIP Dial Peers: Used for routing Voice over IP (VoIP) calls.
  • PSTN Dial Peers: Used for connecting to the Public Switched Telephone Network (PSTN).

3.Matching Criteria:
Dial peers use matching criteria such as destination patterns, incoming/outgoing voice ports, session target addresses, and more to determine which dial peer should handle a particular call.

4.Configuration Example:
dial-peer voice 1 pots
9Tport 0/0/0

Call Legs:

A call leg represents one segment of a call’s journey, from the source to the destination. Each call leg involves a separate set of resources and configurations, such as dial peers and voice ports.

2.Inbound and Outbound Call Legs:

  • Inbound Call Leg: The call leg that handles the incoming call. It involves operations such as matching inbound dial peers, codec negotiation, and connecting the call to the destination.
  • Outbound Call Leg: The call leg responsible for placing the outgoing call. It involves matching outbound dial peers, codec negotiation, and connecting the call to the destination.

3.Call Leg Characteristics:

  • Voice Ports: The physical or virtual interfaces through which voice traffic enters or exits the router.
  • Codecs: The audio compression and decompression algorithms used to encode and decode voice signals.
  • Dial Peers: Define call routing characteristics for matching and connecting calls.

4.Configuration Example:
Copy code
voice-port 0/0/0
voice-class codec 1
cptone US

1.Dial Peer and Call Leg Interaction:

  • Dial peers are used to route calls based on specific criteria.
  • Call legs are the actual instances of calls in progress, involving voice ports, codecs, and other characteristics.

2.Matching and Processing:

  • Inbound dial peers are used to match incoming calls, and outbound dial peers are used to match outgoing calls.
  • Once a dial peer is matched, the associated call leg is created, and the call is processed based on the configurations of that dial peer.

Understanding the interaction between dial peers and call legs is crucial for configuring and managing voice communication on Cisco IOS platforms. This knowledge is particularly important in environments where traditional telephony interfaces coexist with VoIP technologies.

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