IPv4 Address and VLSM

What is the host address of 10.172.189.66 255.255.255.240? (Hint: use binary table)

10.172.189.64 -USE THE BINARY TABLE DUDE Convert host address into binary Host in binary: 00001010.10101100.10111101.01000010 Subnet mast: 11111111.11111111.11111111.11110000 Network address in binary: 00001010.10101100.10111101.01000000 Network address in decimal: 10.172.189.66 See image too, its easier to see than the text.

Public IPv4 Addresses

-Are addresses which are globally routed over the internet. -Must be unique

What is the highest prefix length of a LAN network?

/30 because any higher there won't be enough hosts on each subnet

What is the host IPv4 Address range of the network address 192.168.2.0/24?

192.168.2.1 - 192.168.2.254 (253 possible hosts)

What is the range of an IPv4 Multicast group addresses?

224.0.0.0 - 239.255.255.255

What kind of IP address should Servers and peripherals have?

A predictable static IP address. Use a consistent numbering system for these devices. Peripherals include printers.

Loopback/Local Host addresses

Range: 127.0.0.1-127.255.255.254 (127.0.0.0/8) -Are used by the host to direct traffic back to itself -When pinging 127.0.0.1 you should get replies, if you don't TCP/IP isn't working on the host -Could also ping 127.1.1.1 for example

Link-Local addresses

Range: 169.254.0.0 /16 (169.254.0.1 to 169.254.255.254) -are more commonly known as the Automatic Private IP Addressing (APIPA) or self-assigned addresses. -Are used by a Windows DHCP client to self-configure in the event that there are no DHCP servers available. -Link-local addresses can be used in a peer-to-peer connection but not commonly used for this purpose.

The Private Address Blocks

See Figure Private addresses are defined in RFC 1918 and sometimes referred to as RFC 1918 address space.

Subnetting Network 10.0.0.0/8 using a /16

See figure

What does the IANA do?

The Internet Assigned Numbers Authority manages and allocates blocks of IP addresses to the Regional Internet Registries (RIRs). -5 RIRs are shown in figure

What is the highest address on an IPv4 network?

The broadcast address (IE 192.168.2.255 255.255.255.0)

IPv4 Broadcast Addresses

The limited broadcast address is 255.255.255.255 and is sent to all hosts on the network that the sending host is on because routers don't forward broadcasts by default. The direct broadcast address is sent to all hosts on a specific network

What is a IPv4 network address

it identifies which network the host is on. and is the lowest address on the network. IE 192.168.2.5 255.255.255.0 Network address is: 192.168.2.0

Subnet Mask

In IPv4 it is used to identify the network/host portion of the IPv4 address. The IPv4 subnet mask is used to differentiate the network portion from the host portion of an IPv4 address. When an IPv4 address is assigned to a device, the subnet mask is used to determine the network address of the device. The network address represents all the devices on the same network. Note that the subnet mask does not actually contain the network or host portion of an IPv4 address, it just tells the computer where to look for the part of the IPv4 address that is the network portion and which part is the host portion.

Magic Number Trick (Subnetting)

In the slide the Magic # is 64 Essentially, the last 1 in the subnet dictates by what number the subnets increase. In this case the last 1 is placed in the 2^6 position which is 64 so each of the subnets increase by a factor of 64. IE: 192.168.1.0, 192.168.1.64/26, 192.168.1.128/26, 192.168.1.192/26 How many subnets? There is 2 ones in the last octet so 2^2 = 4 How many hosts per subnet? There are 6 zeros in the last octet so 2^6 = 64 hosts per subnet. Also works with /16 and other subnets

Who manages IPv4 and IPv6 addresses?

Internet Assigned Number Authority (IANA)

What is an IPv4 broadcast address

Is the target IP that can be set to broadcast a frame/packet to all hosts on the network. IE 192.168.2.5 255.255.255.0 Broadcast: 192.168.2.255

What does multicast do?

Multicast transmission reduces traffic by allowing a host to send a single packet to a selected set of hosts that subscribe to a multicast group.

Do routers forward broadcasts?

NO

Is Classful IPv4 addressing used today?

NO -It was replaced by Classless addessing -Classless addressing ignores the rules of classes (A,B,C). -Public network addresses (network addresses and subnet masks) are allocated based on the number of addresses that can be justified.

Can a host be assigned a broadcast and/or network address?

NO, since network is used to identify network and broadcast is used to send message to all hosts on the same network.

NAT

Network Address Translation -Is used to translate between private IPv4 and public IPv4 addresses. -This is usually done on the router that connects the internal network to the ISP network. -Private IPv4 addresses in the organization's intranet will be translated to public IPv4 addresses before routing to the internet Note: Although, a device with a private IPv4 address is not directly accessible from another device across the internet, the IETF does not consider private IPv4 addresses or NAT as effective security measures.

Are private IPv4 addresses globally routed between ISPs?

No, Public IPv4 addresses are globally routed between ISPs.

What must happen to packets with private IP address that are being routed across the inet?

Private addresses in the packet must be discarded or translated to a public address before forwarding the packet to an ISP. Before the ISP can forward this packet, it must translate the source IPv4 address, which is a private address, to a public IPv4 address using Network Address Translation (NAT).

Is 192.0.3.15 a private or public IP?

Public (Private addressing is 192.168.0.0 - 192.168.255.255)

Classless Subnetting Example

The two subnetworks created are: 1. 192.168.1.0/25 2.192.168.1.128/25

DMZ

This is part of the company's network containing resources available to the internet such as a web server. Devices in the DMZ use public IPv4 addresses.

Intranet

This is the internal part of a company's network, accessible only within the organization. Devices in the intranet use private IPv4 addresses.

Problems with Large Broadcast Domains

-A large broadcast domain is an network that connects many hosts. -A problem with a large broadcast domain is that these hosts can generate excessive broadcasts and negatively affect network. -When there is say 400 users on a LAN (lots of hosts) this generates a crap ton of broadcast traffic - this results in slow network operations due to the significant amount of traffic it can cause, and slow device operations because a device must accept and process each broadcast packet. Solution: Reduce the size of the network to create small broadcast domains in a process called subnetting. -These smaller network spaces are called subnets. See figure for subnet demonstration - pay attention to red numbers. In the figure, the 400 users in LAN 1 with network address 172.16.0.0 /16 have been divided into two subnets of 200 users each: 172.16.0.0 /24 and 172.16.1.0 /24. Broadcasts are only propagated within the smaller broadcast domains. Therefore, a broadcast in LAN 1 would not propagate to LAN 2. Notice how the prefix length has changed from a single /16 network to two /24 networks. This is the basis of subnetting: using host bits to create additional subnets. The terms subnet and network are often used interchangeably. Most networks are a subnet of some larger address block.

What can the loop back addresses be used for?

-Can be used for testing to see if TCP/IP is working on a host. -When pinging local host you should get replyies

Subnetting Network 10.0.0.0/8 using a /24 Prefix

-See figure -The /24 boundary is very popular in subnetting because it accommodates a reasonable number of hosts and conveniently subnets at the octet boundary.

What are RIRs responsible for?

-The Regional Internet Registries are responsible for allocating IP addresses to ISPs who provide IPv4 address blocks to organizations and smaller ISPs. -Organizations can also get their addresses directly from an RIR (Subject to the policies of that RIR)

Use Subnetting info

-The more host bits that are borrowed, the more subnets that can be defined. -The more bits that are borrowed to increase the number of subnets reduces the number of hosts per subnet. Networks are most easily subnetted at the octet boundary of /8, /16, and /24. The table identifies these prefix lengths. Notice that using longer prefix lengths decreases the number of hosts per subnet.

VLSM

-Variable Length Subnet Masking -was created because you may have subnets that have more host address than you need and one subnet may require those extra-unused addresses. So you can for example subnet 192.168.1.0/24 to 192.168.1.0/26, 192.168.1.64/26.....192.168.1.192/26 with 64hosts each Then take 192.168.1.192/26 and subnet that into 192.168.1.192/27, 192.168.1.224/27 with 32 hosts each Rules of VLSM 1. Subnets do not have to be equal sizes, as long as their address ranges do not overlap 2.When creating subnets it is easier to work from larger to smaller (so go from larger to smaller)

Prefix Length

-is the number of bits set to 1 in the subnet mask. -It is written in slash notation IE 255.0.0.0 = /8 255.255.0.0 = /16 255.255.255.0 = /24 255.255.255.128 = /25 255.255.255.192 = /26 255.255.255.224 = /27 255.255.255.240 = /28 255.255.255.248 = /29 255.255.255.252 = /30 A network address is also referred to as a prefix or network prefix.

Subnet within an Octet Boundary

-subnets can borrow bits from any host bit position to create other masks. -For instance, a /24 network address is commonly subnetted using longer prefix lengths by borrowing bits from the fourth octet. This provides the administrator with additional flexibility when assigning network addresses to a smaller number of end devices. See figure to see ways to subnet a /24 Network -For each bit borrowed in the fourth octet, the number of subnetworks available is doubled, while reducing the number of host addresses per subnet:

Legacy Classful Addressing (IPv4 Class Ranges)

1. Class A (0.0.0.0/8 to 127.0.0.0/8) - Designed to support extremely large networks with more than 16 million host addresses. Class A used a fixed /8 prefix with the first octet to indicate the network address and the remaining three octets for host addresses (more than 16 million host addresses per network). -Accounts for 50% of IPv4 addresses 2. Class B (128.0.0.0 /16 - 191.255.0.0 /16) - Designed to support the needs of moderate to large size networks with up to approximately 65,000 host addresses. Class B used a fixed /16 prefix with the two high-order octets to indicate the network address and the remaining two octets for host addresses (more than 65,000 host addresses per network). -25% of IPv4 addresses 3. Class C (192.0.0.0 /24 - 223.255.255.0 /24) - Designed to support small networks with a maximum of 254 hosts. Class C used a fixed /24 prefix with the first three octets to indicate the network and the remaining octet for the host addresses (only 254 host addresses per network). -12.5% of IPv4 addresses 4. Class D multicast block consisting of 224.0.0.0 to 239.0.0.0 and a Class E experimental address block consisting of 240.0.0.0 - 255.0.0.0 -12.5% of IPv4 addresses

What are 3 ways to subnet a network?

1. Location (IE by floor) 2. Group or Function (IE administration, students, finance) 3. Device Type (All hosts, All printers, All servers)

Reasons for Segmenting Networks

1. Subnetting reduces overall network traffic and improves network performance. 2. Enables an administrator to implement security policies such as which subnets are allowed or not allowed to communicate together. 3. Another reason is that it reduces the number of devices affected by abnormal broadcast traffic due to misconfigurations, hardware/software problems, or malicious intent.

What Boolean logical operation is used in determining the network address in IPv4?

AND

How to find last host address subnet

AND the subnet masks complement in binary

What is the actual process to identify the network portion and host portion of an IPv4 address

ANDing

What is the lowest address on an IPv4 network?

the network address (IE 192.168.2.0 255.255.255.0)