CIS 81 Fundamentals of Networking Chapter 7: IP Addressing Part 1 – IPv4 CCNA Introduction to Networking 5.0 Rick Graziani Cabrillo College graziani@cabrillo.edu Fall 2015

Number Systems and the Binary Number System

IPv4 Addresses IPv4 Addresses are 32 bit addresses: 1010100111000111010001011000100 10101001 11000111 01000101 10001001 We use dotted notation (or dotted decimal notation) to represent the value of each byte (octet) of the IP address in decimal. 10101001 11000111 01000101 10001001 169 . 199 . 69 . 137

IPv4 Addresses What are the range of addresses? 00000000000000000000000000000000 … 11111111111111111111111111111111 00000000 . 00000000 . 00000000 . 00000000 0 . 0 . 0 . 0 11111111 . 11111111 . 11111111 . 11111111 255 . 255 . 255 . 255

Base 10 (Decimal) Number System Digits (10): 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 Number of: 104 103 102 101 100 10,000’s 1,000’s 100’s 10’s 1’s 1,309 1 3 0 9 99 9 9 100 1 0 0

Number System Rules 1. All digits start with 0 2. A Base-n number system has n number of digits: Decimal: Base-10 has 10 digits Binary: Base-2 has 2 digits Hexadecimal: Base-16 has 16 digits 3. The first column is always the number of 1’s Each of the following columns is n times the previous column (n = Base-n) Base 10: 10,000 1,000 100 10 1 Base 2: 16 8 4 2 1 Base 16: 65,536 4,096 256 16 1

Digits (2): 0, 1 Number of: 27 ___ ___ ___ 23 22 21 20 128’s 8’s 4’s 2’s 1’s Dec. 2 1 0 10 1 0 1 0 17 70 130 255

Digits (2): 0, 1 Number of: 27 26 25 24 23 22 21 20 128’s 64’s 32’s 16’s 8’s 4’s 2’s 1’s Dec. 2 1 0 10 1 0 1 0 17 1 0 0 0 1 70 1 0 0 0 1 1 0 130 1 0 0 0 0 0 1 0 255 1 1 1 1 1 1 1 1

Digits (2): 0, 1 Number of: 27 26 25 24 23 22 21 20 128’s 64’s 32’s 16’s 8’s 4’s 2’s 1’s Dec. 1 0 0 0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 172 192

Digits (2): 0, 1 Number of: 27 26 25 24 23 22 21 20 128’s 64’s 32’s 16’s 8’s 4’s 2’s 1’s Dec. 70 1 0 0 0 1 1 0 40 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 128 1 0 0 0 0 0 0 0 172 1 0 1 0 1 1 0 0 192 1 1 0 0 0 0 0 0

IP Addressing Structure We look at IP addresses using the “dotted decimal format” but network devices only understand the binary format. 11000000 . 10101000 . 00000001 . 00000101

Dotted Decimal Format

Decimal to Binary Assignment

Subnet Mask

Subnet Masks 11111111111111110000000000000000 An IP address is a hierarchical address that is made up of two parts: A network portion A host portion. Subnet Mask Used to define the: Network portion Host portion 32 bits Contiguous set of 1’s followed by a contiguous set of 0’s 1’s: Network portion 0’s: Host portion

Dividing the Network and Host Portions 11111111.11111111.00000000.00000000 Dotted decimal: 255 . 255 . 0 . 0 Slash notation: /16 Expressed as: Dotted decimal Ex: 255.255.0.0 Slash notation or prefix length /16 (the number of one bits)

Hierarchical Network Addressing The IPv4 address with a subnet mask identifies: The network portion The host portion C:\Users\Admin> ipconfig Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : cambrian.cambrianc.on.ca Link-local IPv6 Address . . . . . : fe80::b572:c6c:f983:cadc%11 IPv4 Address. . . . . . . . . . . : 192.168.11.99 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.11.1 C:\Users\Admin>

Subnet Mask: 192.168.11.10 255.255.255.0 192 168 11 10 255 255 255 11111111 11111111 11111111 00000000 The subnet mask identifies which part of the IP address refers to the network. Network Portion Host Portion 192 168 11 The prefix length is the number of bits set to 1 in the subnet mask. It is written in “slash notation”, a “/” followed by the number of bits set to 1. For example: IP address: 192.168.11.10 255.255.255.0 Is the same as: 192.168.11.10 /24

Valid Subnet Mask Values 128 64 32 16 8 4 2 1 Decimal Value 1 128 1 1 192 1 1 1 224 1 1 1 1 240 1 1 1 1 1 248 1 1 1 1 1 1 252 1 1 1 1 1 1 1 254 1 1 1 1 1 1 1 1 255

Subnet Masks So how do hosts figure out which part of the address is the network portion? Hosts AND the IPv4 address and the subnet mask. “1” bits refer to the network portion. “0” bits refer to the host portion. Hosts actually use a the Boolean “AND” operation to accomplish this task. This tells them what network they belong to.

Boolean AND Rules 1 “ANDed” with 1 = 1 0 “ANDed” with 1 = 0 192.168.10.1 /24 0 “ANDed” with anything = 0 IP Address Network Portion Subnet Mask 1 10 168 192 0000 0001 0000 1010 1010 1000 1100 0000 0000 0000 1111 1111 1100 0000 1010 1000 0000 1010 0000 0000 192 168 10

IPv4 AND Subnet Mask >> Network Address

A B 192.168.1.100 255.255.255.0 192.168.2.101 255.255.255.0 Source IPv4 192.168.1.100 Destination IPv4 192.168.2.101 How does the host know if the destination IPv4 address is on it’s network or another network?

Destination MAC Address? Same network? Same Network: Destination IP Address’s MAC Address Different Network: The Default Gateway’s MAC Address The Destination MAC Address will always be one of two addresses. Same network: The MAC address associated with the device’s Destination IP Address. Different network: The MAC address associated with the IP Address of the Default Gateway.

Destination MAC Address? Same network? So, here is the big question: How do does the sending host know if the Source IP Address and Destination IP Address are on the same network?

Destination MAC Address? 192.168.1.10 192.168.1.11 Same network? AND AND My Network = 192.168.1.0 Destination Network = 192.168.1.0 Same network? YES!

Destination MAC Address? 192.168.1.10 192.168.1.11 Same network PC-A’s ARP Cache IPv4 Address MAC Address Check ARP Cache for the destination IPv4 address and a MAC address. Not there? ARP Request

Destination MAC Address? Same network? Same Network: Destination IP Address’s MAC Address Different Network: The Default Gateway’s MAC Address The Destination MAC Address will always be one of two addresses. Same network: The MAC address associated with the device’s Destination IP Address. Different network: The MAC address associated with the IP Address of the Default Gateway.

Review: Destination MAC Address? 192.168.1.100 192.168.2.101 Same network? AND AND My Network = 192.168.1.0 Destination Network = 192.168.2.0 Same network? NO!

Review: Destination MAC Address? 192.168.1.100 192.168.2.101 Different networks PC-A’s ARP Cache IPv4 Address MAC Address Different Network: Need the Default Gateway’s MAC Address Check ARP Cache for IPv4 address of the default gateway and a MAC address. Not there? ARP Request

I only know what I know

Types of Addresses in a Network 192.168.10.0 /24 192.168.10.10 /24 192.168.10.255 /24  Network Address  Host Address  Broadcast Address

Network Address 10.1.1.0 /24 All devices in the network have the same network bits. The network address has all 0 bits in the host portion.

Broadcast Address 10.1.1.255 /24 A broadcast address is used to send data to all hosts in the network. The broadcast address has all 1 bits in the host portion.

Bringing it all together Convert these addresses and masks to Binary (to be used later) Network: 172.0.0.0 10101100.00000000.00000000.00000000 Mask: 255.0.0.0 11111111.00000000.00000000.00000000 172.255.255.255 10101100.11111111.11111111.11111111 Broadcast Address Network: 172.16.0.0 10101100.00010000.00000000.00000000 Mask: 255.255.0.0 11111111.11111111.00000000.00000000 172.16.255.255 10101100.00010000.11111111.11111111

Bringing it all together Convert these addresses and masks to Binary (to be used later) Network: 192.168.1.0 11000000.10101000.00000001.00000000 Mask: 255.255.255.0 11111111.11111111.11111111.00000000 Bcst: 192.168.1.255 11000000.10101000.00000001.11111111 Network: 192.168.0.0 11000000.10101000.00000000.00000000 Mask: 255.255.0.0 11111111.11111111.00000000.00000000 Bcst: 192.168.255.255 11000000.10101000.11111111.11111111 Bcst: 192.168.0.255 11000000.10101000.00000000.11111111

Bringing it all together Convert these addresses and masks to Binary (to be used later) Network: 10.1.1.0 00001010.00000001.00000001.00000000 Mask: /24 11111111.11111111.11111111.00000000 Bcast: 10.1.1.255 00001010.00000001.00000001.11111111 Network: 10.2.0.0 00001010.00000010.00000000.00000000 Mask: /16 11111111.11111111.00000000.00000000 Bst:10.2.255.255 00001010.00000010.11111111.11111111 Network 10.0.0.0 00001010.00000000.00000000.00000000 Bcast10.0.255.255 00001010.00000000.11111111.11111111

Host Address 10.1.1.10 /24 In IPv4 addresses, host addresses are the addresses between the network address and the broadcast address devices in that network. The host address does not have all 0 bits or all 1 bits in the host portion. It is important to identify the first host address and the last host address. Hosts within a network can be assigned IP addresses within this range.

1st Host Address The host portion of the first host address will contain all 0 bits with a 1 bit for the lowest order or right-most bit. (“All 0’s and a 1.”) This address is always one greater than the network address. For example the first host address is 10.1.1.1 /24. NOTE: It is common in many addressing schemes to use the first host address for the router or default gateway address.

Last Host Address The host portion of the last host address will contain all 1 bits with a 0 bit for the lowest order or right-most bit. (“All 1’s and a 0.”) This address is always one less than the broadcast address. For example, the last host address is 10.1.1.254.

Range of hosts – Your Turn! Host Addresses in binary 172.0.0.0 (net) 10101100.00000000.00000000.00000000 255.0.0.0 (SM) 11111111.00000000.00000000.00000000 172.0.0.1 10101100.00000000.00000000.00000001 172.255.255.254 10101100.11111111.11111111.11111110 172.255.255.255 10101100.11111111.11111111.11111111 (broadcast) 172.16.0.0 (net) 10101100.00010000.00000000.00000000 255.255.0.0 (SM) 11111111.11111111.00000000.00000000 172.16.0.1 10101100.00010000.00000000.00000001 172.16.255.254 10101100.00010000.11111111.11111110 172.16.255.255 10101100.00010000.11111111.11111111

Range of hosts – Your Turn! Host Addresses in binary 192.168.1.0 (net) 11000000.10101000.00000001.00000000 255.255.255.0(SM) 11111111.11111111.11111111.00000000 192.168.1.1 11000000.10101000.00000001.00000001 192.168.1.254 11000000.10101000.00000001.11111110 192.168.1.255 11000000.10101000.00000001.11111111 (broadcast) 192.168.0.0 (net) 11000000.10101000.00000000.00000000 255.255.0.0 (SM) 11111111.11111111.00000000.00000000 192.168.0.1 11000000.10101000.00000000.00000001 192.168.255.254 11000000.10101000.11111111.11111110 192.168.255.255 11000000.10101000.11111111.11111111

Range of hosts – Your Turn! Host Addresses in binary 192.168.0.0 (net) 11000000.10101000.00000000.00000000 255.255.255.0(SM) 11111111.11111111.11111111.00000000 192.168.0.1 11000000.10101000.00000000.00000001 192.168.0.254 11000000.10101000.00000000.11111110 192.168.0.255 11000000.10101000.00000000.11111111 (broadcast)

Range of hosts – The rest… Host Addresses in binary 10.1.1.0 (net) 00001010.00000001.00000001.00000000 /24 (SM) 11111111.11111111.11111111.00000000 10.1.1.1 00001010.00000001.00000001.00000001 10.1.1.254 00001010.00000001.00000001.11111110 10.1.1.255 00001010.00000001.00000001.11111111 (broadcast) 10.2.0.0 (net) 00001010.00000010.00000000.00000000 /16 (SM) 11111111.11111111.00000000.00000000 10.2.0.1 00001010.00000010.00000000.00000001 10.2.255.254 00001010.00000010.11111111.11111110 10.2.255.255 00001010.00000010.11111111.11111111

Range of hosts – The rest… Host Addresses in binary 10.0.0.0 (net) 00001010.00000000.00000000.00000000 /16 (SM) 11111111.11111111.00000000.00000000 10.0.0.1 00001010.00000000.00000000.00000001 10.0.255.254 00001010.00000000.11111111.11111110 10.0.255.255 00001010.00000000.11111111.11111111 (broadcast)

Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries 172.1.16.0 10101100.00000001.00010000.00000000 255.255.240.0 11111111.11111111.11110000.00000000 172.1.16.1 10101100.00000001.00010000.00000001 … 172.1.31.254 10101100.00000001.00011111.11111110 172.1.31.255 10101100.00000001.00011111.11111111 (broadcast) Number of hosts: 212 – 2 = 4,096 – 2 = 4,094 hosts

Non-natural boundary masks Host Addresses in binary 10.1.16.0 (net) 00001010.00000001.00010000.00000000 /20 (SM) 11111111.11111111.11110000.00000000 10.1.16.1 00001010.00000001.00010000.00000001 10.1.31.254 00001010.00000001.00011111.11111110 10.1.31.255 00001010.00000001.00011111.11111111 (broadcast) 10.2.0.32 (net) 00001010.00000010.00000000.00100000 /28 (SM) 11111111.11111111.11111111.11110000 10.2.0.33 00001010.00000010.00000000.00100001 10.2.0.46 00001010.00000010.00000000.00101110 10.2.255.47 00001010.00000010.00000000.00101111

Practice!

Addresses for User Devices

Addresses for User Devices Hosts are assigned IP addresses from the range of available addresses in the network. These IP addresses can be assigned either: Statically Dynamically

Static Assignment Useful for printers, servers, and other networking devices that do not change location often and need to be accessible to clients on the network based on a fixed IP address. Increased control of network resources. However, static addressing can be time-consuming to enter on each host.

Dynamic Assignment Instead of manually assigning IP addresses (subnet mask, default gateway, DNS addresses), it is easier to have IP addresses assigned automatically. This is done using Dynamic Host Configuration Protocol (DHCP). The DHCP server requires that a block of addresses, called an address pool, is used for assigning to the DHCP clients on a network.

How Does DHCP Work? A DHCP Server must be available. It must have a pre-configured range (scope) of IP addresses. As clients come online they contact the DHCP server and request an address. The DHCP server chooses an address and allocates it to that host.

DHCP Server Scope

How Does DHCP Work? Client Boots DHCP Discover DHCP Request DHCP Offer Mac Address DHCP Request IP, MAC Address Client DHCP Server DHCP Offer IP, Lease time DHCP Ack IP, Lease time

Dynamic Addressing 58

Dynamic vs. Static IP Addressing Quiz Desktop computer Server Router Switch Laptop IP phone Printer RADIUS server AP PDA iTouch Fridge Static IP Address Dynamic (DHCP) IP Address

Unicast, Multicast, and Broadcast

Destination Unicasts, Multicasts, and Broadcasts Source IP addresses are always unicast Unicasts: Packet travels from one host to another specific host. Multicasts: Packet travels from one host to a select number of other hosts. Supports voice and audio broadcasts, news feeds, distribution of software, re-imaging clients off peak times. Broadcasts: Packet travels from one host to all hosts on the local network.

Unicast Addresses 62

Multicast Addresses For example: One hosts sends packets to the multicast IP address 224.10.10.5/24. Multicast clients subscribe to the multicast group and listen for packets destined to 224.10.10.5. 63

Broadcast Addresses Directed broadcast is sent to all hosts on a specific network. An example destination IPv4 address is 192.168.1.255 /24. Limited broadcast is to all hosts on the local network. These packets use a destination IPv4 address 255.255.255.255. 64

Private vs. Public Addresses

Private Addresses Most IPv4 addresses are public IP addresses. These are reachable IPv4 addresses on the Internet. However, there are blocks of addresses that are private addresses and are never propagated on the Internet. Packets with a source or destination private IP address are not propagated by Internet routers. Internet routers / firewalls block or translate these addresses. Private addresses are usually converted to public IP addresses using NAT (Network Address Translation)

Private Addresses Private addresses are defined in RFC 1918. The private address blocks are: 10.0.0.0 /8: 10.0.0.0 to 10.255.255.255 172.16.0.0 /12: 172.16.0.0 to 172.31.255.255 192.168.0.0 /16: 192.168.0.0 to 192.168.255.255 RFC 6598, IANA reserved 100.64.0.0/10 known as shared address space. Similar to RFC 1918, but intended only for use in service provider networks.

Other Special Addresses Refer to RFC 3330 Loopback address: 127.0.0.1 127.0.0.0 – 127.255.255.255 Hosts use to direct traffic to themselves. Link-Local addresses: 169.254.0.0/16 169.254.0.0 – 169.254.255.255 Host can automatically assign itself an address if it has none. TEST-NET addresses: 192.0.2.0 to 192.0.2.255 (192.0.2.0 /24) 68

Special Addresses TEST-NET Addresses 192.0.2.0 to 192.0.2.255 (192.0.2.0 /24) The address block is set aside for teaching and learning purposes and are sometimes used in documentation and network examples. You may often find these addresses used with the domain names example.com or example.net in RFCs, vendor, and protocol documentation. Addresses within this block should not appear on the Internet. 69

How addressing space use to be assigned. Classful Addressing How addressing space use to be assigned. Historically, RFC1700 grouped the unicast ranges into specific sizes referred to as Classful addressing for IPv4 (never existed for IPv6): Class A, B, and C addresses: 0.0.0.0 - 223.255.255.255 Multicast addresses: 224.0.0.0 - 239.255.255.255 Experimental addresses: 240.0.0.0 - 255.255.255.254 70

IPv4 Address Classes Class A /8 Class B /16 Class C /24

Total Possible Addresses IPv4 Address Classes Address Class # of Possible Networks # of Possible Hosts Total Possible Addresses Class A Class B Class C 126 16,777,214 532,676,608 1,073,709,056 2,113,928,964 16,384 65,534 2,097,152 254 Class A. 255.0.0.0 or /8 Was reserved for governments and extremely large organizations. Class B. 255.255.0.0 or /8 Was reserved for medium/large organizations. Class C. 255.255.255.0 or /24 Was for every other organization (small organizations).

How the ranges were determined First First Network Host Class Bits Octet Bits Bits A 0 0 – 127 8 24 B 10 128 - 191 16 16 C 110 192 - 223 24 8 D 1110 224 – 239 E 1111 240 - 255

Fill in the information… 1. 192.168.1.3 Class C Default Mask: 255.255.255.0 Network: 192.168.1.0 Broadcast: 192.168.1.255 Hosts: 192.168.1.1 through 192.168.1.254 2. 1.12.100.31 Class A Default Mask: 255.0.0.0 Network: 1.0.0.0 Broadcast: 1.255.255.255 Hosts: 1.0.0.1 through 1.255.255.254 3. 172.30.77.5 Class B Default Mask: 255.255.0.0 Network: 172.30.0.0 Broadcast: 172.30.255.255 Hosts: 172.30.0.1. through 172.30.255.254

Class separates network from host bits The Class determines the Base Network Mask! 1. 192.168.1.3 Class C Default Mask: 255.255.255.0 Network: 192.168.1.0 2. 1.12.100.31 Class A Default Mask: 255.0.0.0 Network: 1.0.0.0 3. 172.30.77.5 Class B Default Mask: 255.255.0.0 Network: 172.30.0.0

Total Possible Addresses IP Address Allocation Initially, IP addresses were allocated to organizations based on request rather than need. Address Class # of Possible Networks # of Possible Hosts Total Possible Addresses Class A Class B Class C 126 16,777,214 532,676,608 1,073,709,056 2,113,928,964 16,384 65,534 2,097,152 254

IP Address Allocation – Visual Perspective Class A Total Nets: 126 Total Hosts/Net: 16,777,214 Class C Total Nets: 2,097,152 Total Hosts/Net: 254 The Internet is now based on a Classless addressing scheme. NOTE: Class B Total Nets: 16,384 Total Hosts/Net: 65,534

11111111.00000000.00000000.00000000 /8 (255.0.0.0) 16,777,216 host addresses 11111111.10000000.00000000.00000000 /9 (255.128.0.0) 8,388,608 host addresses 11111111.11000000.00000000.00000000 /10 (255.192.0.0) 4,194,304 host addresses 11111111.11100000.00000000.00000000 /11 (255.224.0.0) 2,097,152 host addresses 11111111.11110000.00000000.00000000 /12 (255.240.0.0) 1,048,576 host addresses 11111111.11111000.00000000.00000000 /13 (255.248.0.0) 524,288 host addresses 11111111.11111100.00000000.00000000 /14 (255.252.0.0) 262,144 host addresses 11111111.11111110.00000000.00000000 /15 (255.254.0.0) 131,072 host addresses 11111111.11111111.00000000.00000000 /16 (255.255.0.0) 65,536 host addresses 11111111.11111111.10000000.00000000 /17 (255.255.128.0) 32,768 host addresses 11111111.11111111.11000000.00000000 /18 (255.255.192.0) 16,384 host addresses 11111111.11111111.11100000.00000000 /19 (255.255.224.0) 8,192 host addresses 11111111.11111111.11110000.00000000 /20 (255.255.240.0) 4,096 host addresses 11111111.11111111.11111000.00000000 /21 (255.255.248.0) 2,048 host addresses 11111111.11111111.11111100.00000000 /22 (255.255.252.0) 1,024 host addresses 11111111.11111111.11111110.00000000 /23 (255.255.254.0) 512 host addresses 11111111.11111111.11111111.00000000 /24 (255.255.255.0) 256 host addresses 11111111.11111111.11111111.10000000 /25 (255.255.255.128) 128 host addresses 11111111.11111111.11111111.11000000 /26 (255.255.255.192) 64 host addresses 11111111.11111111.11111111.11100000 /27 (255.255.255.224) 32 host addresses 11111111.11111111.11111111.11110000 /28 (255.255.255.240) 16 host addresses 11111111.11111111.11111111.11111000 /29 (255.255.255.248) 8 host addresses 11111111.11111111.11111111.11111100 /30 (255.255.255.252) 4 host addresses 11111111.11111111.11111111.11111110 /31 (255.255.255.254) 2 host addresses 11111111.11111111.11111111.11111111 /32 (255.255.255.255) “Host Route” ISPs no longer restricted to three classes. Can now allocate a large range of network addresses based on customer requirements

Public Addresses

Public Addresses Public addresses are required on the Internet and they must be unique. The use of public addresses is regulated and allocated to each organization separately. RIRs (Regional Internet Registries) typically provide public addresses to ISPs. Companies obtain their IPv4 address blocks from an ISP. In a sense, the ISP loans or rents these addresses to the organization.

RIRs These registration companies are called Regional Internet Registries (RIRs). IANA ARIN (American Registry for Internet Numbers) North America Region http://www.arin.net RIPE NCC (Reseaux IP Europeans) Europe, the Middle East, and Central Asia http://www.ripe.net APNIC (Asia Pacific Network Information Centre) Asia/Pacific Region http://www.apnic.net AfriNIC (African Network Information Centre) Africa Region http://www.afrinic.net LACNIC (Regional Latin-American and Caribbean IP Address Registry) Latin America and some Caribbean Islands http://www.lacnic.net

The 3 Tiers of ISP ISPs are designated by a hierarchy based on their level of connectivity to the Internet backbone. Each lower tier obtains connectivity to the backbone via a connection to a higher tier ISP. The Internet backbone is built on a three tier hierarchy. Tier 1 = AT&T, Verizon (UUNET), SAVVIS, Sprintlink, Bell, Level 3 Networks, Qwest, … Tier 2 = Cogent, Eastlink, Orion, Canarie, nLayer, France Télécom, … Tier 3 = Local ISPs

The 3 Tiers of ISPs RIR ARIN Tier 1 Sprint SAVVIS … Tier 2 Tier 3 Tiers 1 ISPs have multiple, direct connections to the Internet backbone. Primarily serves very large companies and Tier 2 ISPs. Sprint SAVVIS … Connect to the Internet via Tier 1 ISPs. Primarily serves large companies and Tier 3 ISPs. Tier 2 nLayer Cogent … Connect to the Internet via Tier 2 ISPs. Primarily serves homes, and small to medium companies. Tier 3 Fortress ITX Beachcomputers …

CIS 81 Fundamentals of Networking IP Addressing Part 1 – IPv4 CCNA Introduction to Networking 5.0 Rick Graziani Cabrillo College graziani@cabrillo.edu