You need to configure port security on switch R1. Which two statements are true about this technology? (Choose two)

A.
Port security can be configured for ports supporting VoIP.

B.
With port security configured, four MAC addresses are allowed by default.

C.
The network administrator must manually enter the MAC address for each device in order for the switch to allow connectivity.

D.
With port security configured, only one MAC addresses is allowed by default.

E.
Port security cannot be configured for ports supporting VoIP.

Explanation:

You can use the port security feature to restrict input to an interface by limiting and identifying MAC addresses of the workstations that are allowed to access the port. When you assign secure MAC addresses to a secure port, the port does not forward packets with source addresses outside the group of defined addresses. If you limit the number of secure MAC addresses to one and assign a single secure MAC address, the workstation attached to that port is assured the full bandwidth of the port.

This feature is indeed supported on voice VLAN ports. If you enable port security on a port configured with a voice VLAN and if there is a PC connected to the CiscoIPPhone, Cisco tells us to set the maximum allowed secure addresses on the port to at least 3.

The table below shows the default number of allowed MAC addresses is one.
Default Port Security Configuration

Feature Default Setting

Port security Disabled on a port

Maximum number of secure MAC 1
addresses

Violation mode Shutdown. The port shuts down when the maximum number of secure MAC
addresses is exceeded, and an SNMP
trap notification is sent.

Reference: Configuring Port Security

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.1E/native/configuration/guide/port_sec.html#wpxref25516