Skinny is a protocol used in VoIP applications. (Skinny is another name for the Simple Client Control Protocol [SCCP].) Cisco IP Phones, Cisco CallManager, and Cisco CallManager Express use this protocol. Figure 8-13 demonstrates the registration and communication process between a Cisco IP Phone and all the respective components such as Cisco CallManager.

Figure 8-13. Cisco IP Phone Registration and Communication Flow

In Figure 8-13, the Cisco IP Phone is assigned to a specific VLAN. After that, it sends a request to the DHCP server to get an IP address, DNS server address, and TFTP server name or address. It also gets a default gateway address if you have set these options in the DHCP server.


If a TFTP server name is not included in the DHCP reply, the Cisco IP Phone uses the default server name.

The Cisco IP Phone obtains its configuration from the TFTP server. It resolves the Cisco CallManager name via DNS and starts the Skinny registration process.

The Cisco ASA inspects the Skinny transactions with the use of the inspect skinny command. This command is enabled by default.


Cisco ASA does not support fragmented Skinny messages.

As previously discussed, Cisco IP Phones download their configuration information from a TFTP server. This information includes the name or IP address of the Cisco CallManager server to which they need to connect. You must use an ACL to open UDP port 69 when the Cisco IP Phones are on a lower security interface compared to the TFTP server. If the Cisco IP Phones are on a lower security interface compared to the Cisco CallManager, create a static NAT entry for the Cisco CallManager.


Instructions on how to create ACLs and static NAT entries are covered in Chapter 5, "Network Access Control."

Part I: Product Overview

Introduction to Network Security

Product History

Hardware Overview

Part II: Firewall Solution

Initial Setup and System Maintenance

Network Access Control

IP Routing

Authentication, Authorization, and Accounting (AAA)

Application Inspection

Security Contexts

Transparent Firewalls

Failover and Redundancy

Quality of Service

Part III: Intrusion Prevention System (IPS) Solution

Intrusion Prevention System Integration

Configuring and Troubleshooting Cisco IPS Software via CLI

Part IV: Virtual Private Network (VPN) Solution

Site-to-Site IPSec VPNs

Remote Access VPN

Public Key Infrastructure (PKI)

Part V: Adaptive Security Device Manager

Introduction to ASDM

Firewall Management Using ASDM

IPS Management Using ASDM

VPN Management Using ASDM

Case Studies

Cisco Asa(c) All-in-one Firewall, IPS, And VPN Adaptive Security Appliance
Cisco ASA: All-in-One Firewall, IPS, and VPN Adaptive Security Appliance
ISBN: 1587052091
EAN: 2147483647
Year: 2006
Pages: 231 © 2008-2020.
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