Cisco Systems OL-8356-01 User Manual

CHA PTER

Phone Hardening

To tighten security on the phone, you can perform tasks in the Phone Configuration window in
Cisco CallManager Administration. This chapter contains information on the following topics:

• Disabling the Gratuitous ARP Setting, page 9-1

• Disabling Web Access Setting, page 9-1

• Disabling the PC Voice VLAN Access Setting, page 9-2

• Disabling the Setting Access Setting, page 9-2

• Disabling the PC Port Setting, page 9-2

• Configuring Phone Hardening, page 9-3

• Where to Find More Information, page 9-3

9

Disabling the Gratuitous ARP Setting

By default, Cisco IP Phones accept Gratuitous ARP packets. Gratuitous ARP packets, which devices
use, announce the presence of the device on the network. However, attackers can use these packets to
spoof a valid network device; for example, an attacker could send out a packet that claims to be the
default router. If you choose to do so, you can disable Gratuitous ARP in the Phone Configuration
window of Cisco CallManager Administration.

Note Disabling this functionality does not prevent the phone from identifying its default router.

Disabling Web Access Setting

Disabling the web server functionality for the phone blocks access to the phone internal web pages,
which provide statistics and configuration information. Features, such as Cisco Quality Report Tool, do
not function properly without access to the phone web pages. Disabling the web server also affects any
serviceability application, such as CiscoWorks, that relies on web access.

To determine whether the web services are disabled, the phone parses a parameter in the configuration
file that indicates whether the services are disabled or enabled. If the web services are disabled, the
phone does not open the HTTP port 80 for monitoring purposes and blocks access to the phone internal
web pages.

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Cisco CallManager Security Guide

9-1

Disabling the PC Voice VLAN Access Setting

Disabling the PC Voice VLAN Access Setting

By default, Cisco IP Phones forward all packets that are received on the switch port (the one that faces
the upstream switch) to the PC port. If you choose to disable the PC Voice VLAN Access setting in the
Phone Configuration window of Cisco CallManager Administration, packets that are received from the
PC port that use voice VLAN functionality will drop. Various Cisco IP Phone models use this
functionality differently.

• Cisco IP Phone 7940 and 7960 drop any packets that are tagged with the voice VLAN, in or out of

the PC port.

• Cisco IP Phone 7970 drops any packet that contains an 802.1Q tag on any VLAN, in or out of the

PC port.

• Cisco IP Phone 7912 cannot perform this functionality.

Disabling the Setting Access Setting

By default, pressing the Settings button on a Cisco IP Phone provides access to a variety of information,
including phone configuration information. Disabling the Setting Access setting in the Phone
Configuration window of Cisco CallManager Administration prohibits access to all options that
normally display when you press the Settings button on the phone; for example, the Contrast, Ring Type,
Network Configuration, Model Information, and Status settings.

The preceding settings do not display on the phone if you disable the setting in Cisco CallManager
Administration. If you disable this setting, the phone user cannot save the settings that are associated
with the Volume button; for example, the user cannot save the volume.

Chapter 9 Phone Hardening

Disabling this setting automatically saves the current Contrast, Ring Type, Network Configuration,
Model Information, Status, and Volume settings that exist on the phone. To change these phone settings,
you must enable the Setting Access setting in Cisco CallManager Administration.

Disabling the PC Port Setting

By default, Cisco CallManager enables the PC port on all Cisco IP Phones that have a PC port. If you
choose to do so, you can disable the PC Port setting in the Phone Configuration window of
Cisco CallManager Administration. Disabling the PC port proves useful for lobby or conference room
phones.

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Cisco CallManager Security Guide

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