Physical & Logical Address

COMP 315

MAC Address• A media access control address (MAC address) is a unique identifier

assigned to network interfaces for communications on the physical network segment.

• MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet. Logically, MAC addresses are used in the media access control protocol sublayer media access control protocol sublayer of the OSI reference model.

• Short for Media Access Control address, a hardware address that uniquely identifies each node of a network. In IEEE 802 networks, the Data Link Control (DLC) layer of the OSI Reference Model is divided into two sub-layers: the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. The MAC layer interfaces directly with the network medium. Consequently, each different type of network medium requires a different MAC layer.

• On networks that do not conform to the IEEE 802 standards but do conform to the OSI Reference Model, the node address is called the Data Link Control (DLC) address.

MAC Address

• MAC addresses are most often assigned by the manufacturer of a network interface controller (NIC) and are stored in its hardware, such as the card's read-only memory or some other firmware mechanism.

• If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number and may be referred to as the burned-in address (BIA).

MAC Address

MAC addresses are formed according to the rules of one of three numbering name spaces managed by the Institute of Electrical and Electronics Engineers (IEEE): MAC-48, EUI-48, and EUI-64. The IEEE claims trademarks on the names EUI-48 and EUI-64, in which EUI is an abbreviation for Extended Unique Identifier.

MAC Address

• The standard (IEEE 802) format for printing MAC-48 addresses in human-friendly form is six groups of two hexadecimal digits, separated by hyphens (-) or colons (:), in transmission order (e.g. 01-23-45-67-89-ab or 01:23:45:67:89:ab ).

• This form is also commonly used for EUI-64. Another convention used by networking equipment uses three groups of four hexadecimal digits separated by dots (.) (e.g. 0123.4567.89ab ), again in transmission order.

MAC Address

MAC Address

• The original IEEE 802 MAC address comes from the original Xerox Ethernet addressing scheme.

• This 48-bit address space contains potentially 248 or 281,474,976,710,656 possible MAC addresses.

MAC Address

• The first three octets (in transmission order) identify the organization that issued the identifier and are known as the Organizationally Unique Identifier (OUI ).

• The following three (MAC-48 and EUI-48) or five (EUI-64) octets are assigned by that organization in nearly any manner they please, subject to the constraint of uniqueness.

How to find the MAC Address

ipconfig ipconfig command

Logical Address (IP Address)

• IP address is short for Internet Protocol (IP) address.

• An IP address is an identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination.

The Format of an IP Address

• An IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.

• Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates.

• An IP address can be static or dynamic. A static IP address will never change and it is a permanent Internet address. A dynamic IP address is a temporary address that is assigned

each time a computer or device accesses the Internet.

The Format of an IP Address

• The four numbers in an IP address are used in different ways to identify a particular network and a host on that network. Four regional Internet registries -- ARIN, RIPE NCC, LACNIC and APNIC-- assign Internet addresses from the following three classes:

• Class A - supports 16 million hosts on each of 126 networksClass B - supports 65,000 hosts on each of 16,000 networksClass C - supports 254 hosts on each of 2 million networks

The Format of an IP Address

• The number of unassigned Internet addresses is running out, so a new classless scheme called CIDR is gradually replacing the system based on classes A, B, and C and is tied to adoption of IPv6.

• In IPv6 the IP address size is increased from 32 bits to 128 bits.

CIDR

• Short for Classless Inter-Domain Routing, an IP addressing scheme that replaces the older system based on classes A, B, and C. With CIDR, a single IP address can be used to designate many unique IP addresses. A CIDR IP address looks like a normal IP address except that it ends with a slash followed by a number, called the IP network prefix. For example: 172.200.0.0/16

• The IP network prefix specifies how many addresses are covered by the CIDR address, with lower numbers covering more addresses. An IP network prefix of /12, for example, can be used to address 1,048,576 former Class C addresses.

What is My IP Address?

• To view your IP address you can use the ipconfig (IPCONFIG) command line tool. Ipconfig displays all current TCP/IP network configuration values and refreshes Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) settings.

• To launch the command prompt from a Windows-based computer click: StartStart > > All ProgramsAll Programs > > AccessoriesAccessories > > Command PromptCommand Prompt. Type . Type ipconfigipconfig and hit enter.

• You can also use Google search to find your IP address. Type what is my IP addresswhat is my IP address as a search query and Google will show the IP address of the computer from which the query was received as the top search result.

IPv4 Format

IPv6

• IPv6 (Internet Protocol Version 6) is also called IPng (Internet Protocol next generation) and it is the newest version of the Internet Protocol (IP) reviewed in the IETF standards committees to replace the current version of IPv4 (Internet Protocol Version 4).

IPv6• IPv6 is an Internet Protocol (IP) for packet-switched internetworking that

specifies the format of packets (also called datagrams) and the addressing scheme across multiple IP networks. In comparing the two protocols IPv6 expands upon the addressing and routing capabilities of IPv4 in a number of ways including:

– In IPv6 the IP address size is increased from 32 bits to 128 bits – IPv6 supports a greater number of addressable nodes – IPv6 provides more levels of addressing hierarchy – IPv6 offers simpler auto-configuration of addresses – Ipv6 also supports simplified header format

IPv6

• Increasing the IP address pool was a major factor in the development of IPv6. The biggest benefit of IPv6 is that it will replace the IPv4 32-bit address scheme with a much longer 128-bit address scheme.

• The IPv4 32-bit address scheme allows for a total of 232 addresses while IPv6 allows for 2128 total addresses.

IPv6 Format

Historical classful network architecture

Class Leadingbits

Size of networknumber bit field

Size of restbit field

Numberof networks

Addressesper network

Start address

End address

A 0 8 24 128 (27) 16,777,216 (224) 0.0.0.0 127.255.25

5.255

B 10 16 16 16,384 (214) 65,536 (216) 128.0.0.0 191.255.255.255

C 110 24 8 2,097,152 (221) 256 (28) 192.0.0.0 223.255.255.255

IANA-reserved private IPv4 network ranges

Start End No. of addresses

24-bit block (/8 prefix, 1 × A) 10.0.0.0 10.255.255.255 1677721620-bit block (/12 prefix, 16 × B) 172.16.0.0 172.31.255.255 1048576

16-bit block (/16 prefix, 256 × C) 192.168.0.0 192.168.255.255 65536

Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnetssubnets; for example, many home routers automatically use a default address range of 192.168.0.0 through 192.168.0.255 (192.168.0.0/24).

The Internet Assigned Numbers Authority (IANA) Internet Assigned Numbers Authority (IANA) manages the IP address space allocations globally and delegates five regional Internet registries (RIRs) to allocate IP address blocks to local Internet registries (Internet service providers) and other entities.