Network+ Chapter 8: Subnets and VLANs

What is the least number of bits you would need to borrow from the network portion of a class B subnet mask to get at least 130 hosts per subnet? A. None B. Eight C. Nine D. Ten

- B. Eight

How many bits of a Class A IP address are used for host information? A. 8 bits B. 16 bits C. 24 bits D. 32 bits

- C. 24 bits - Class A | nnnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh | 8 bits NetworkID | 24 bits HostPortion

Which hexadecimal block in an IPv6 address is used for the Subnet ID? A. The first one B. The third one C. The fourth one D. The eighth one

- C. The fourth one - The fourth hexadecimal block in the site prefix can be altered to create subnets within a site.

What is the network ID with CIDR notation for the IP address 172.16.32.108 whose subnet mask is 255.255.255.0?

- 172.16.32.108/24 "0"

Which VLAN is designed to support administrative access to network devices?

- Management VLAN, can be used to provide administrative access to a switch, By default, this might be the same as the default VLAN; however, this poses a security risk and should be changed.

Suppose your company has leased one Class C license, 120.10.10.0, and wants to sublease the first half of these IP addresses to another company. What is the CIDR notation for the subnet to be subleased? What is the subnet mask for this network?

- 120.10.10.0/25 the second half "1" or /25 - 255.255.255.128

Which formulas can be used to calculate the magic number? Choose two. A. 256 - the interesting octet B. 2^h - 2 C. 2^n D. 2^h

- A. 256 - the interesting octet - B. 2^h - 2 - The unusual octet is often called the interesting octet. Subtracting the interesting octet value from 256 and you get what is called the magic number.

While designing your network's VLAN topology, your team has decided to use a centrally managed DHCP server rather than creating a separate DHCP server for each VLAN. What software will you need in order to make the central DHCP server accessible across VLANs? A. DHCP relay agent B. DHCP server C. Hypervisor D. Virtual router

- A. DHCP Relay Agent - Run a DCHP server for the entire network and use a DHCP Relay Agent to help sort DHCP requests by subnet.

What do well-chosen subnets accomplish? A. IP address spaces overlap for easier management. B. Network documentation is easier to manage. C. Routing efficiency is decreased by ensuring IP address spaces are not mathematically related. D. Problems affect the entire network making them more difficult to pin down.

- C. Routing efficiency is decreased by ensuring IP address spaces are not mathematically related.

Which of the following is not a good reason to segment a network? A. To limit access to broadcast domains B. To reduce the demand on bandwidth C. To increase the number of networking devices on a network D. To narrow down the location of problems on a network

- C. To increase the number of networking devices on a network

What is the formula for determining the number of possible hosts on a network? A. 2^n = Y B. 2^n - 2 = Y C. 2^h = Z D. 2^h - 2 = Z

- D. 2^h - 2 = Z - As a shortcut to calculating the number of hosts, you can use the formula: 2^h - 2 = Z - h equals the number of bits remaining in the host portion - Z equals the number of hosts available in each subnet.

Which IEEE standard determines how VLANs work on a network? A. 802.1x B. 802.11 C. 802.3af D. 802.1Q

- D. 802.1Q - 802.1Q standard, which is the IEEE standard that defines how VLAN information appears in frames and how switches interpret that information.

Which port mode on a switch enables that port to manage traffic for multiple VLANs? A. Console B. Ethernet C. Access D. Trunk

- D. Trunk - Trunk port, connects the switch to a router or another switch (or possibly a server). This interface manages traffic from multiple VLANs

What area of a network can provide less stringent security, so a webserver is more accessible from the open Internet?

- Enhance security, Webservers, can be made more accessible to the open Internet than the rest of the network, for example, a DMZ (demilitarized zone) can provide an area of the network with less stringent security for these purposes.

An attacker configures a VLAN frame with two tags instead of just one. The first tag directs the frame to the authorized VLAN. After the frame enters the first VLAN, the switch appropriately removes the tag, then discovers the next tag, and sends the frame along to a protected VLAN, which the attacker is not authorized to access. What kind of attack is this?

- Hackers sometimes take advantage of the way VLANs are tagged to implement an attack called VLAN hopping. The attacker generates transmissions that appear, to the switch, to belong to a protected VLAN, then crosses VLANs to access sensitive data or inject harmful software. - Double Tagging, the hacker stacks VLAN tags in Ethernet frames. When the first, legitimate tag is removed by a switch, the second, illegitimate tag is revealed, tricking a switch into forwarding the transmission on to a restricted VLAN.

Subnetting operates at Layer _____ while VLANs function at Layer _____.

- Layer 3 - Layer 2 - At Layer 3 you can use subnetting to organize devices within the available IP address space, whether the LANs are defined physically or virtually. - VLANs (virtual local area network or virtual LAN) groups port on a Layer 2 switch so that some of the local traffic on the switch is forced to go through a router, thereby limiting the traffic to a smaller broadcast domain.

Which VLAN on a switch manages untagged frames?

- Native VLAN, receives all untagged frames from untagged ports.

Which Cisco command lists configured VLANs on a switch?

- The show vlan command is used to list the current VLANs recognized by a switch.

On which networking device do you configure VLANS?

- VLANs can only be implemented through managed switches, whose ports can be partitioned into groups.

Which IP addressing technique subnets a subnet to create subnets of various sizes?

- VLSM (variable length subnet mask) allows subnets to be further subdivided into smaller and smaller groupings until each subnet is about the same size as the necessary IP address space. This is often referred to as "subnetting the subnet".