ICND1 Chapter 11

What is the private IP network(s) for class A networks and what is the number of networks for that private address space?

10.0.0.0, 1 Network

Network Part

The portion of an IPv4 address that is either 1, 2, or 3 octets/bytes long, based on whether the address is in a Class A, B, or C network.

What is the private IP network(s) for class B networks and what is the number of networks for that private address space?

172.16.0.0-172.31.0.0, 16 Networks

What is the private IP network(s) for class C networks and what is the number of networks for that private address space?

192.168.0.0-192.168.255.0, 256 Networks

The number of IP addresses in a classful network can be calculated with what formula?

2(to the power of host bits)-2

Subnet Mask

A 32-bit number that numerically describes the format of an IP address, by representing the combined network and subnet bits in the address with mask bit values of 1, and representing the host bits in the address with mask bit values of 0.

Before Class B network 172.16.0.0 is subnetted by a network engineer, what parts of the structure of the IP addresses in this network already exist, with a specific size? (Select two answers.) a. Network b. Subnet c. Host d. Broadcast

A and C. An unsubnetted Class A, B, or C network has two parts: the network and host parts

Which of the following are private IP networks? (Select two answers.) a. 172.31.0.0 b. 172.32.0.0 c. 192.168.255.0 d. 192.1.168.0 e. 11.0.0.0

A and C. The private IPv4 networks, defined by RFC 1918, are Class A network 10.0.0.0, the 16 Class B networks from 172.16.0.0 to 172.31.0.0, and the 256 Class C networks that begin with 192.168.

Subnet Broadcast Address

A special address in each subnet, specifically the largest numeric address in the subnet, designed so that packets sent to this address should be delivered to all hosts in that subnet.

Host Part

A term used to describe a part of an IPv4 address that is used to uniquely identify a host inside a subnet. The host part is identified by the bits of value 0 in the subnet mask.

Which of the following are public IP networks? (Select three answers.) a. 9.0.0.0 b. 172.30.0.0 c. 192.168.255.0 d. 192.1.168.0 e. 1.0.0.0

A, D, and E. The private IPv4 networks, defined by RFC 1918, are Class A network 10.0.0.0, the 16 Class B networks from 172.16.0.0 to 172.31.0.0, and the 256 Class C networks that begin with 192.168. The three correct answers are from the public IP network range, and none are reserved values.

A Class B network needs to be subnetted such that it supports 100 subnets and 100 hosts/subnet. Which of the following answers list a workable combination for the number of network, subnet, and host bits? (Select two answers.) a. Network = 16, subnet = 7, host = 7 b. Network = 16, subnet = 8, host = 8 c. Network = 16, subnet = 9, host = 7 d. Network = 8, subnet = 7, host = 17

B and C. At least 7 subnet bits are needed, because 26 = 64, so 6 subnet bits could not number 100 different subnets. Seven subnet bits could, because 27 = 128 => 100. Similarly, 6 host bits is not enough, because 26 - 2 = 62, but 7 host bits is enough, because 27 - 2 = 126 => 100. The number of network, subnet, and host bits must total 32 bits, making one of the answers incorrect. The answer with 8 network bits cannot be correct because the question states that a Class B network is used, so the number of network bits must always be 16. The two correct answers have 16 network bits (required because the question states the use of a Class B network), and at least 7 subnet and host bits each.

Host A is a PC, connected to switch SW1 and assigned to VLAN 1. Which of the following are typically assigned an IP address in the same subnet as host A? (Select two answers) a. The local router's WAN interface b. The local router's LAN interface c. All other hosts attached to the same switch d. Other hosts attached to the same switch and also in VLAN 1

B and D. The general rule to determine whether two devices' interfaces should be in the same subnet is whether the two interfaces are separated from each other by a router. To provide a way for hosts in one VLAN to send data to hosts outside that VLAN, a local router must connect its LAN interface to the same VLAN as the hosts, and have an address in the same subnet as the hosts. All the hosts in that same VLAN on the same switch would not be separated from each other by a router, so these hosts would also be in the same subnet. However, another PC, connected to the same switch but in a different VLAN, will require its packets to flow through a router to reach Host A, so Host A's IP address would need to be in a different subnet compared to this new host.

A network engineer spends time thinking about the entire Class B network 172.16.0.0, and how to subnet that network. He then chooses how to subnet this Class B network and creates an addressing and subnetting plan, on paper, showing his choices. If you compare his thoughts about this network before subnetting the network, to his thoughts about this network after mentally subnetting the network, which of the following occurred to the parts of the structure of addresses in this network? a. The subnet part got smaller. b. The host part got smaller. c. The network part got smaller. d. The host part was removed. e. The network part was removed.

B. An unsubnetted Class A, B, or C network has two parts: the network and host parts. To perform subnetting, the engineer creates a new subnet part by borrowing host bits, shrinking the number of host bits. The subnet part of the address structure exists only after the engineer chooses a nondefault mask. The network part remains a constant size.

Which of the following terms are not used to reference the one number in each subnet used to uniquely identify the subnet? (Select two answers.) a. Subnet ID b. Subnet number c. Subnet broadcast d. Subnet name e. Subnet address

C and D. Subnet ID (short for subnet identifier), subnet address, and subnet number

Why does the formula for the number of hosts per subnet (2H - 2) require the subtraction of two hosts? a. To reserve two addresses for redundant default gateways (routers) b. To reserve the two addresses required for DHCP operation c. To reserve addresses for the subnet ID and default gateway (router) d. To reserve addresses for the subnet broadcast address and subnet ID

D. By definition, two address values in every IPv4 subnet cannot be used as host IPv4 addresses: the first (lowest) numeric value in the subnet for the subnet ID, and the last (highest) numeric value in the subnet for the subnet broadcast address.

Subnet Number

In IPv4, a dotted-decimal number that represents all addresses in a single subnet. Numerically, the smallest value in the range of numbers in a subnet, reserved so that it cannot be used as a unicast IP address by a host.

Subnet Part

In a subnetted IPv4 address, interpreted with classful addressing rules, one of three parts of the structure of an IP address, with the subnet part uniquely identifying different subnets of a classful IP network.

NAT

Network Address Translation, allows multiple companies to use the exact same private IP network, using the same IP addresses as other companies, while still connecting to the Internet

Subnet

Subdivisions of a Class A, B, or C network, as configured by a network administrator. Subnets allow a single Class A, B, or C network to be used instead of multiple networks, and still allow for a large number of groups of IP addresses, as is required for efficient IP routing.

The capability to specify a different subnet mask for the same Class A, B, or C network number on different subnets. VLSM can help optimize available address space.

The capability to specify a different subnet mask for the same Class A, B, or C network number on different subnets. VLSM can help optimize available address space.

In the 1990's what solutions were developed to help with the filling up of the public IP address space?

• A new version of IP (IPv6), with much larger addresses (128 bit) • Assigning a subset of a public IP network to each company, instead of an entire public IP network, to reduce waste • Network Address Translation (NAT), which allows the use of private IP networks

To make routing work efficiently, IP addressing rules group addresses into groups called subnets. The rules are?

• Addresses in the same subnet are not separated by a router. • Addresses in different subnets are separated by at least one router.

Each subnet reserves the first and last numbers in the group, and these two numbers cannot be used as IP addresses. In particular, each subnet contains the following

• Subnet number: Also called the subnet ID or subnet address, this number identifies the subnet. It is the numerically smallest number in the subnet. It cannot be used as an IP address by a host. • Subnet broadcast: Also called the subnet broadcast address or directed broadcast address, this is the last (numerically highest) number in the subnet. It also cannot be used as an IP address by a host. • IP addresses: All the numbers between the subnet ID and the subnet broadcast address can be used as a host IP address.

You should plan to have one subnet for every?

• VLAN • Point-to-point serial link • Ethernet emulation WAN link (EoMPLS) • Frame Relay PVC (permanent virtual circuits )