Overview; Required Network Components - Cisco 7941G - Unified IP Phone VoIP Administration Manual

Understanding Security Features for Cisco Unified IP Phones

Overview

Required Network Components

Cisco Unified IP Phone 7961G/7961G-GE and 7941G/7941G-GE for Cisco Unified Communications Manager 6.1
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Cisco Unified IP phones and Cisco Catalyst switches have traditionally used
Cisco Discovery Protocol (CDP) to identify each other and determine parameters
such as VLAN allocation and inline power requirements. However, CDP is not
used to identify any locally attached PCs; therefore, Cisco Unified IP Phones
provide an EAPOL pass-through mechanism, whereby a PC locally attached to
the IP phone, may pass through EAPOL messages to the 802.1X authenticator in
the LAN switch. This prevents the IP phone from having to act as the
authenticator, yet allows the LAN switch to authenticate a data end point prior to
accessing the network.
In conjunction with the EAPOL pass-through mechanism, Cisco Unified IP
Phones provide a proxy EAPOL-Logoff mechanism. In the event that the locally
attached PC is disconnected from the IP phone, the LAN switch would not see the
physical link fail, because the link between the LAN switch and the IP phone is
maintained. To avoid compromising network integrity, the IP phone sends an
EAPOL-Logoff message to the switch, on behalf of the downstream PC, which
triggers the LAN switch to clear the authentication entry for the downstream PC.
The Cisco Unified IP phones also contain an 802.1X supplicant, in addition to the
EAPOL pass-through mechanism. This supplicant allows network administrators
to control the connectivity of IP phones to the LAN switch ports. The IP phone
802.1X supplicant implements the EAP-MD5 option for 802.1X authentication.
Support for 802.1X authentication on Cisco Unified IP Phones requires several
components, including:
Cisco Unified IP Phone—The phone acts as the 802.1X supplicant, which
•
initiates the request to access the network.
• Cisco Secure Access Control Server (ACS) (or other third-party
authentication server)—The authentication server and the phone must both be
configured with a shared secret that is used to authenticate the phone.
Cisco Catalyst Switch (or other third-party switch)—The switch must support
•
802.1X to act as the authenticator and pass the messages between the phone
and the authentication server. When the exchange is completed, the switch
then grants or denies the phone access to the network.
Chapter 1 An Overview of the Cisco Unified IP Phone
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