CCNA 2 v7 Modules 10 – 13: L2 Security and WLANs Test Online

Hint

In a small network with a few network devices, AAA authentication can be implemented with the local database and with usernames and passwords stored on the network devices. Authentication using the TACACS+ or RADIUS protocol will require dedicated ACS servers although this authentication solution scales well in a large network.

Hint

Both discovery protocols can provide hackers with sensitive network information. They should not be enabled on edge devices, and should be disabled globally or on a per-interface basis if not required. CDP is enabled by default.​

Hint

Telnet uses plain text to communicate in a network. The username and password can be captured if the data transmission is intercepted. SSH encrypts data communications between two network devices. TFTP and SCP are used for file transfer over the network. SNMP is used in network management solutions.

Hint

When the MAC address table is full, the switch treats the frame as an unknown unicast and begins to flood all incoming traffic to all ports only within the local VLAN.

Hint

The devices involved in the 802.1X authentication process are as follows:

• The supplicant, which is the client that is requesting network access
• The authenticator, which is the switch that the client is connecting to and that is actually controlling physical network access
• The authentication server, which performs the actual authentication

Hint

Manual configuration of the single allowed MAC address has been entered for port fa0/12. PC1 has a different MAC address and when attached will cause the port to shut down (the default action), a log message to be automatically created, and the violation counter to increment. The default action of shutdown is recommended because the restrict option might fail if an attack is underway.

Hint

Spoofing DTP messages forces a switch into trunking mode as part of a VLAN-hopping attack, but VLAN double tagging works even if trunk ports are disabled. Changing the native VLAN from the default to an unused VLAN reduces the possibility of this type of attack. DHCP spoofing and DHCP starvation exploit vulnerabilities in the DHCP message exchange.​

Hint

DAI can be configured to check for both destination or source MAC and IP addresses:

• Destination MAC – Checks the destination MAC address in the Ethernet header against the target MAC address in the ARP body.
• Source MAC – Checks the source MAC address in the Ethernet header against the sender MAC address in the ARP body.
• IP address – Checks the ARP body for invalid and unexpected IP addresses including addresses 0.0.0.0, 255.255.255.255, and all IP multicast addresses.

Hint

BPDU guard can be enabled on all PortFast-enabled ports by using the spanning-tree portfast bpduguard default global configuration command. Alternatively, BPDU guard can be enabled on a PortFast-enabled port through the use of the spanning-tree bpduguard enable interface configuration command.

Hint

With sticky secure MAC addressing, the MAC addresses can be either dynamically learned or manually configured and then stored in the address table and added to the running configuration file. In contrast, dynamic secure MAC addressing provides for dynamically learned MAC addressing that is stored only in the address table.

Hint

Beacons are the only management frame that may regularly be broadcast by an AP. Probing, authentication, and association frames are used only during the association (or reassociation) process.

Hint

Two methods can be used by a wireless device to discover and register with an access point: passive mode and active mode. In passive mode, the AP sends a broadcast beacon frame that contains the SSID and other wireless settings. In active mode, the wireless device must be manually configured for the SSID, and then the device broadcasts a probe request.

Hint

Channels 1, 6, and 11 are selected because they are 5 channels apart. thus minimizing the interference with adjacent channels. A channel frequency can interfere with channels on either side of the main frequency. All wireless devices need to be used on nonadjacent channels.

Hint

Active is a mode used to configure an access point so that clients must know the SSID to connect to the access point. APs and wireless routers can operate in a mixed mode meaning that that multiple wireless standards are supported. Open is an authentication mode for an access point that has no impact on the listing of available wireless networks for a client. When an access point is configured in passive mode, the SSID is broadcast so that the name of wireless network will appear in the listing of available networks for clients.

Hint

802.11ac provides data rates up to 1.3 Gb/s and is still backward compatible with 802.11a/b/g/n devices. 802.11g and 802.11n are older standards that cannot reach speeds over 1Gb/s. 802.11ad is a newer standard that can offer theoretical speeds of up to 7 Gb/s.

Hint

The first action a technician should do to secure a new wireless network is to change the default user-name and password of the wireless router. The next action would usually be to configure encryption. Then once the initial group of wireless hosts have connected to the network, MAC address filtering would be enabled and SSID broadcast disabled. This will prevent new unauthorized hosts from finding and connecting to the wireless network.

Hint

The Cisco 3504 WLC dashboard displays when a user logs into the WLC. It provides some basic settings and menus that users can quickly access to implement a variety of common configurations. By clicking the Advanced button, the user will access the advanced Summary page and access all the features of the WLC.

Hint

Each new WLAN configured on a Cisco 3500 series WLC needs its own VLAN interface. Thus it is required that a new VLAN interface to be created first before a new WLAN can be created.

Hint

Wireless range is determined by the access point antenna and output power, not the frequency band that is used. In this scenario it is stated that all users have wireless NICs that comply with the latest standard, and so all can access the 5 GHz band. Although some users may find it inconvenient to switch to the 5 Ghz band to access streaming services, it is the greater number of channels, not just fewer users, that will improve network performance.

Hint

The RADIUS protocol uses security features to protect communications between the RADIUS server and clients. A shared secret is the password used between the WLC and the RADIUS server. It is not for end users.

Hint

As soon as an AP is taken out of a box, the default device password, SSID, and security parameters (wireless network password) should be set. The frequency of a wireless antenna can be adjusted, but doing so is not required. The beacon time is not normally configured. The wireless client operating system password is not affected by the configuration of a home wireless network.

Hint

Cisco provides solutions to help mitigate Layer 2 attacks including these:

• IP Source Guard (IPSG) – prevents MAC and IP address spoofing attacks
• Dynamic ARP Inspection (DAI) – prevents ARP spoofing and ARP poisoning attacks
• DHCP Snooping – prevents DHCP starvation and SHCP spoofing attacks
• Port Security – prevents many types of attacks including MAC table overflow attacks and DHCP starvation attacks

Web Security Appliance (WSA) is a mitigation technology for web-based threats.

Hint

Mitigating a VLAN 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.

Hint

The Port Security line simply shows a state of Enabled if the switchport port-security command (with no options) has been entered for a particular switch port. If a port security violation had occurred, a different error message appears such as Secure-shutdown. The maximum number of MAC addresses supported is 50. The Maximum MAC Addresses line is used to show how many MAC addresses can be learned (2 in this case). The Sticky MAC Addresses line shows that only one device has been attached and learned automatically by the switch. This configuration could be used when a port is shared by two cubicle-sharing personnel who bring in separate laptops.

Hint

Remote Authentication Dial-In User Service (RADIUS) is a protocol and server software that provides user-based authentication for an organization. When a WLAN is configured to use a RADIUS server, users will enter username and password credentials that are verified by the RADIUS server before allowing to the WLAN.

Hint

Splitting the wireless traffic between the 802.11n 2.4 GHz band and the 5 GHz band will allow for the 802.11n to use the two bands as two separate wireless networks to help manage the traffic, thus improving wireless performance.

Hint

Denial of service attacks can be the result of improperly configured devices which can disable the WLAN. Accidental interference from devices such as microwave ovens and cordless phones can impact both the security and performance of a WLAN. Man-in-the-middle attacks can allow an attacker to intercept data. Rogue access points can allow unauthorized users to access the wireless network.

Hint

CAPWAP is an IEEE standard protocol that enables a WLC to manage multiple APs and WLANs. CAPWAP is also responsible for the encapsulation and forwarding of WLAN client traffic between an AP and a WLC.

Hint

The violation mode can be viewed by issuing the show port-security interface <int>command. Interface FastEthernet 0/1 is configured with the violation mode of protect. If there is a violation, interface FastEthernet 0/1 will drop packets with unknown MAC addresses.

Hint

By using TACACS+ or RADIUS, AAA can authenticate users from a database of usernames and passwords stored centrally on a server such as a Cisco ACS server.

Hint

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 to lease the entire pool of available IP addresses, thus denying them to legitimate hosts.

Hint

A double-tagging (or double-encapsulated) VLAN hopping attack takes advantage of the way that hardware on most switches operates. Most switches perform only one level of 802.1Q de-encapsulation, which allows an attacker to embed a hidden 802.1Q tag inside the frame. This tag allows the frame to be forwarded to a VLAN that the original 802.1Q tag did not specify. An important characteristic of the double-encapsulated VLAN hopping attack is that it works even if trunk ports are disabled, because a host typically sends a frame on a segment that is not a trunk link. This type of attack is unidirectional and works only when the attacker is connected to a port residing in the same VLAN as the native VLAN of the trunk port.

Hint

One of the components in AAA is accounting. After a user is authenticated through AAA, AAA servers keep a detailed log of exactly what actions the authenticated user takes on the device.

Hint

The DHCP snooping configuration includes building the DHCP Snooping Binding Database and assigning necessary trusted ports on switches. A trusted port points to the legitimate DHCP servers. In this network design, because the DHCP server is attached to AS3, seven switch ports should be assigned as trusted ports, one on AS3 toward the DHCP server, one on DS1 toward AS3, one on DS2 toward AS3, and two connections on both AS1 and AS2 (toward DS1 and DS2), for a total of seven.

Hint

If no violation mode is specified when port security is enabled on a switch port, then the security violation mode defaults to shutdown.

Hint

SSID cloaking is a weak security feature that is performed by APs and some wireless routers by allowing the SSID beacon frame to be disabled. Although clients have to manually identify the SSID to be connected to the network, the SSID can be easily discovered. The best way to secure a wireless network is to use authentication and encryption systems. SSID cloaking does not provide free Internet access in public locations, but an open system authentication could be used in that situation.

Hint

WPA and WPA2 come in two types: personal and enterprise. Personal is used in home and small office networks. Shared key allows three different authentication techniques: (1) WEP, (2) WPA, and (3) 802.11i/WPA2. WEP is an encryption method.

Hint

Because some users are complaining about the network being too slow, the correct option would be to split the traffic so that there are two networks using different frequencies at the same time. Replacing the wireless NICs will not necessarily correct the network being slow and it could be expensive for the company. DHCP versus static addressing should have no impact of the network being slow and it would be a huge task to have all users assigned static addressing for their wireless connection. Upgrading the firmware on the wireless access point is always a good idea. However, if some of the users are experiencing a slow network connection, it is likely that this would not substantially improve network performance.

Hint

Simple Network Management Protocol (SNMP) is used to monitor the network.

Hint

Any address with the 10 in the first octet is a private IPv4 address and cannot be routed on the internet. The wireless router will use a service called Network Address Translation (NAT) to convert private IPv4 addresses to internet-routable IPv4 addresses for wireless devices to gain access to the internet.

Hint

Many wireless routers have an option for configuring quality of service (QoS). By configuring QoS, certain time-sensitive traffic types, such as voice and video, are prioritized over traffic that is not as time-sensitive, such as email and web browsing.

Hint

A VLAN hopping attack enables traffic from one VLAN to be seen by another VLAN without routing. In a basic VLAN hopping attack, the attacker takes advantage of the automatic trunking port feature enabled by default on most switch ports.

Hint

One of the components in AAA is authorization. After a user is authenticated through AAA, authorization services determine which resources the user can access and which operations the user is allowed to perform.

Hint

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.

Hint

When DHCP snooping is being configured, the number of DHCP discovery messages that untrusted ports can receive per second should be rate-limited by using the ip dhcp snooping limit rate interface configuration command. When a port receives more messages than the rate allows, the extra messages will be dropped.

Hint

On a Cisco switch, an interface can be configured for one of three violation modes, specifying the action to be taken if a violation occurs:Protect – Packets with unknown source addresses are dropped until a sufficient number of secure MAC addresses are removed, or the number of maximum allowable addresses is increased. There is no notification that a security violation has occurred. Restrict – Packets with unknown source addresses are dropped until a sufficient number of secure MAC addresses are removed, or the number of maximum allowable addresses is increased. In this mode, there is a notification that a security violation has occurred. Shutdown – The interface immediately becomes error-disabled and the port LED is turned off.

Hint

By default, dual-band routers and APs use the same network name on both the 2.4 GHz band and the 5 GHz band. The simplest way to segment traffic is to rename one of the wireless networks.

Hint

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.