Implementing Network Security ( Version 2.0) – CCNAS Chapter 6 Exam Online

The security violation counter for Fa0/2 has been incremented (evidenced by the 1 in the SecurityViolation column). The most secure addresses allowed on port Fa0/2 is 1 and that address was manually entered. Therefore, PC1 must have a different MAC address than the one configured for port Fa0/2. Connections between end devices and the switch, as well as connections between a router and a switch, are made with a straight-through cable.

The PVLAN Edge feature does not allow one device to see traffic that is generated by another device. Ports configured with the PVLAN Edge feature are also known as protected ports. BPDU guard prevents unauthorized connectivity to a wired Layer 2 switch. SPAN is port mirroring to capture data from one port or VLAN and send that data to another port. DTP (Dynamic Trunking Protocol) is automatically enabled on some switch models to create a trunk if the attached device is configured for trunking. Cisco recommends disabling DTP as a best practice.

The port security feature can be used to limit how many MAC addresses can be learned on a switch port and help prevent MAC address table overflow attacks. Storm control is a feature that can prevent excessive broadcasts and multicasts from disrupting other LAN traffic. These functions are not provided by Network Admission Control (NAC).

Root guard prevents the placement of the root bridge from changing by blocking any port that receives a superior BPDU. A superior BPDU is one with a higher root bridge ID than the currently selected root bridge has.

Port security limits the number of source MAC addresses allowed through a switch port. This feature can prevent an attacker from flooding a switch with many spoofed MAC addresses.

Root guard in conjunction with PortFast, and BPDU guard is used to prevent an STP manipulation attack.

The Cisco NAC Agent is a lightweight agent that runs on endpoint devices. The function of this agent is to perform deep inspection of the security profile of the endpoints. This includes inspecting the registry settings, services, and files.

Cisco NAC authenticates users and assess the policy compliance of the device the user is using to connect to the network. The role of the Cisco NAC Manager is to define the security policies of user access and endpoint security policies.

Cisco NAC is used in the Cisco Borderless Network Architecture to authenticate users and ensure user devices are compliant with security policies. The Cisco NAC server assesses and enforces security policy compliance.

Cisco NAC is used in the Cisco Borderless Network Architecture to authenticate users and ensure that user devices are compliant with security policies. The Cisco NAC Guest Server manages guest network access and the ability to create guest accounts.

The goal of both the Cisco NAC framework and the Cisco NAC Appliance is to ensure that only hosts that are authenticated and have their security posture examined and approved are permitted onto the network. They provide four important functions: authentication, authorization, and accounting; posture assessment (evaluating an incoming device against the security policies), quarantining of non-compliant systems, and remediation of noncompliant devices. They do not provide VPN connection or intrusion detection/prevention services.

The Antimalware Protection (AMP) security solution can enable malware detection and blocking, continuous analysis, and retrospective alerting with the following:​File reputation – analysis of files inline and blocking or applying policies
File sandboxing – analysis of unknown files to understand true file behavior
File retrospection – continuing to analyze files for changing threat levels

Port security is the most effective method for preventing CAM table overflow attacks. Port security gives an administrator the ability to manually specify what MAC addresses should be seen on given switch ports. It provides a method for limiting the number of MAC addresses that can be dynamically learned over a switch port.

As a result of a CAM table attack, a switch can run out of memory resources to store MAC addresses. When this happens, no new MAC addresses can be added to the CAM table and the switch will forward all received frames to all other ports. This would allow an attacker to capture all traffic that is flooded by the switch.

Like Dynamic ARP Inspection (DAI), IP Source Guard (IPSG) needs to determine the validity of MAC-address-to-IP-address bindings. To do this IPSG uses the bindings database built by DHCP snooping.

Mitigating a VLAN hopping attack can be done by disabling Dynamic Trunking Protocol (DTP), manually setting ports to trunking mode, and by setting the native VLAN of trunk links to VLANs not in use.

Two methods can be used by Dynamic ARP Inspection (DAI) to determine the validity of MAC-address-to-IP-address bindings. One is a bindings database built by DHCP snooping. The other method is through the use of user-configured ARP ACLs.

Mitigating a VLAN hopping attack can be done by disabling Dynamic Trunking Protocol (DTP) and by setting the native VLAN of trunk links to a VLAN not in use.

DCHP starvation attacks are launched by an attacker with the intent to create a DoS for DHCP clients. To accomplish this goal, the attacker uses a tool that sends many DHCPDISCOVER messages in order to lease the entire pool of available IP addresses, thus denying them to legitimate hosts.

PVLANs are used to provide Layer 2 isolation between ports within the same broadcast domain. The level of isolation can be specified
with three types of PVLAN ports:Promiscuous ports that can forward traffic to all other ports
Isolated ports that can only forward traffic to promiscuous ports
Community ports that can forward traffic to other community ports and promiscuous ports

There are several recommended STP stability mechanisms to help mitigate STP manipulation attacks:

• PortFast – Used to immediately bring an interface configured as an access or trunk port to the forwarding state from a blocking state. This is applied to all end-user ports.
• BPDU guard – Immediately error-disables a port that receives a BPDU. This is applied to all end-user ports.
• Root guard – Prevents a switch from becoming the root switch. Applied to all ports where root switch should not be located.
• Loop guard – Detects unidirectional links to prevent alternate or root ports from becoming designated ports. Applied to all ports that are or can become non-designated.

A client can connect to the Cisco CWS service directly by using a proxy autoconfiguration (PAC) file installed on the end device. The Cisco CWS connector is a software component integrated into four Cisco products including Cisco ASA, Cisco WSA, and Cisco AnyConnect Secure Mobility Client. A client can use the Cisco CWS service through these products.

BPDU guard immediately error-disables a port that receives a BPDU. This prevents rogue switches from being added to the network. BPDU guard should only be applied to all end-user ports.

When DHCP snooping is enabled, a switch will deny packets containing unauthorized DHCP server messages coming from an untrusted port.