Mod 9 – IP Addressing Part 1 CIS151 Paul Morris MHCC

2 Identifying Network Users The network layer is responsible for moving data through a set of networks. Protocols that support network layer use hierarchical addressing Protocols that have no network layer only work on small internal networks. Protocols that have no network layer use a flat addressing scheme that does not scale well

3 Application Header + data Data Encapsulation Example … Application Layer Layer 4: Transport Layer Layer 3: Network Layer Layer 2: Network Layer Layer 1: Physical Layer

4 Addressing: Network & Host Network address help to identify route through the network cloud Network address divided into two parts: –Network –host Different network protocols have their own methods of dividing the network address into network and host portions.

5 Path Determination Path determination is determined by Routing Protocols (OSPF, EIGRP, RIP, etc.) - later

6 Network Addressing: Network & Host Phone numbers are similar to network addresses –Area Code / Phone Number –503 – –503  Network Portion –  Host Portion –503  NW Oregon –  Paul Morris, MHCC

7 Network Addressing: Network & Host Mt. Hood Community Coll. Paul Morris SE Stark St. Gresham, OR Your Name 123 Main Street Anytown, ST ZIP codes direct your mail to your local post office and your neighborhood. The street address then directs the carrier to your home.

8 Computer Mobility Layer 2 (Ethernet) and Layer 3 (IP) Addresses are needed: Layer 2 / MAC address –Physically burned into the NIC –Doesn’t change –The device’s real identity Layer 3 / Protocol address –Set with software –The device’s “mailing” address –Needs to change when device is moved

9 What is the MAC and IP Address on my computer?

10 Flat versus Hierarchical Layer 2 - Flat addressing schemes –Next available –Social Security Number –MAC addresses Layer 3 - Hierarchical addressing schemes –Phone numbers –ZIP codes –IP addresses

11 Layer 2 Addresses = Flat Addressing If the Internet was a flat network with only layer 2 addresses, switches would need to know the millions of layer 2 host addresses or broadcast the frame as an unknown unicast.

12 Layer 3 Addresses = Organized by Network MHCCPSUYour ISP Layer 3 Addresses are organized by network. To know the layer 3 address, means you know what network this packet belongs to. Routers maintain lists of layer 3 network addresses to route the packet to the right network. Layer 2 addresses are still used! Hosts will have both Layer 2 and Layer 3 addresses. We will see how these work together a little later.

13 IP Addressing Scheme IP Addresses are 32 bits. Where the network part ends ant the host part begins depends on the subnet mask (coming). Divide into four 8 bit sections (octets). Convert from binary to decimal.

14 IP – Layer 3 Application Header + data

15 IP Addresses The 32 bits of an IP address are grouped into 4 bytes: We use dotted notation (or dotted decimal notation) to represent the value of each byte (octet) of the IP address in decimal

16 IP Addresses An IP address has two parts: –network number –host number Which bits refer to the network number? Which bits refer to the host number?

17 IP Addresses Answer: Newer technology - Classless IP Addressing –The subnet mask determines the network portion and the host portion. –Value of first octet does NOT matter (older classful IP addressing) –Hosts and Classless Inter-Domain Routing (CIDR). –Classless IP Addressing is what is used within the Internet and in most internal networks. Older technology - Classful IP Addressing –Value of first octet determines the network portion and the host portion. –Used with classful routing protocols like RIPv1. –The Cisco IP Routing Table is structured in a classful manner (sem2).

18 Classless IP Addressing This chapter discusses Classless IP Addressing Next we will discuss Classful IP Addressing

19 IP Addressing Network ID or Network Portion –Host on a network can only communicate directly with devices if they have the same network ID, same network, same subnet. –The subnet mask determines the network portion and the host portion. –All zeros in the host portion of the address. Note: Need to check the mask as the network address can be a 0. –Routers use the network ID when it forwards data on the Internet –Network IDs cannot be used as an address for any device that is attached to the network, such as hosts, router interfaces, etc.

20 Using the subnet mask The subnet mask is what tells you what part of the IP address is the network portion and which part of the IP address is the host portion. When getting an IP address, either a host address or a network address, from an ISP (Internet Service Provider), they also provide you with a subnet mask. As you will see in a moment, you can modify this subnet mask (make it longer), to subnet your own network further.

21 Subnet Masks - Binary Subnet Mask A “1” bit in the subnet mask means that the corresponding bit in the IP address should be read as a network number A “0” bit in the subnet mask means that the corresponding bit in the IP address should be read as a host bit NetworkHost Network Host Network Host 1st octet2nd octet3rd octet4th octet

22 Subnet Masks – dotted decimal Subnet Mask: or /8 Subnet Mask: or /16 Subnet Mask: or / /n “slash” tells us how many “1” bits are in the subnet mask. Subnet masks do not have to end on “natural octet boundaries” –Network Addresses have all zeros in the host portion of the address NetworkHost Network Host Network Host 1st octet2nd octet3rd octet4th octet

23 Subnet Masks Subnet Mask: or /8 Subnet Mask: or /16 Subnet Mask: or / /n “slash” tells us how many “1” bits are in the subnet mask. Subnet masks do not have to end on “natural octet boundaries” NetworkHost Network Host Network Host 1st octet2nd octet3rd octet4th octet

24 Subnet Masks – dotted decimal Subnet Mask: or /16 Subnet Mask: or / Need to check the mask as an octet in the network address can be a Network Host Network Host 1st octet2nd octet3rd octet4th octet

25 Why the mask matters: Number of hosts! NetworkHost Network Host Network Host 1st octet2nd octet3rd octet4th octet Subnet Mask: or / or / or /24 Subnet masks do not have to end on “natural octet boundaries”

26 Subnet: (/8) NetworkHost 8 bits With 24 bits available for hosts, there a 2 24 possible addresses. That’s 16,777,216 nodes! There are a possibility of 126 /8 networks. 16,777,214 host addresses, one for network address and one for broadcast address. Only large organizations such as the military, government agencies, universities, and large corporations have networks with these many addresses. Cable Modem ISPs have and Pacbell DSL users have Cable Modem ISPs

27 Subnet: (/16) Network Host 8 bits With 16 bits available for hosts, there a 2 16 possible addresses. That’s 65,536 nodes! There are a possibility of 16,384 /16 networks 65,534 host addresses, one for network address and one for broadcast address.

28 Subnet: (/24) Network Host 8 bits With 8 bits available for hosts, there a 2 8 possible addresses. That’s 256 nodes! There are 2,097,152 possible /24 networks. 254 host addresses, one for network address and one for broadcast address.

29 IP Addresses There is a tradeoff between: The number of network bits and the number of networks you can have… AND The number of HOST bits and the number of hosts for each network you can have.

30 Subnet Masks – Your Turn! Underline the network portion of each address: Network Address Subnet Mask / / /16 What is the other portion of the address?

31 Subnet Masks – Your Turn! Underline the network portion of each address: Network Address Subnet Mask / / /16 What is the other portion of the address? –Host Addresses

32 IP Addressing Broadcast Address –Used to send data to all devices on the network –All ones in the host portion of the address –All devices pay attention to a broadcast –Broadcast addresses cannot be used as an address for any device that is attached to the network. –What are the broadcast addresses for these networks?

33 Subnet Masks – Your Turn! What is the broadcast address of each network: Network Address Subnet MaskBroadcast Address / / /16

34 Subnet Masks – Your Turn! What is the broadcast address of each network: Network Address Subnet MaskBroadcast Address / / /

35 Subnet Masks – Your Turn! Convert these addresses to Binary (to be used later)

36 Subnet Masks – Your Turn! Convert these addresses to Binary (to be used later)

37 Subnet Masks – Your Turn! Convert these addresses to Binary (to be used later) / / /

38 Addressing: Network & Host Routers are required when two hosts with IP addresses on different networks or subnets need to communicate. What are some example Host IP addresses?

39 Host Addresses Network Addresses include a range of HOST IP addresses For every network (or subnet) two address cannot be used for HOST IP addresses: 1.Network Address – The address that represents the network. 2.Broadcast Address – The address used to communicate with all devices on the network.

40 Addressing Hosts Network Host One network address, 65,534 hosts, one broadcast address Etc Network Address 1 Broadcast Address 65,534 Host Addresses Given the address with the subnet mask:

41 Subnet Masks – Your Turn! Host addresses are all addresses between the network address and the broadcast address: What is the range of host addresses for each network? Network Address Subnet MaskBroadcast Address / / /

42 Subnet Masks – Your Turn! Network Address Subnet MaskBroadcast Address through through through through through

43 Subnet Masks – Your Turn! Network Address Subnet MaskBroadcast Address / through / through / through

44 Subnet Masks – Your Turn! Host Addresses in binary (net) (SM) (broadcast) (net) (SM) (broadcast)

45 Subnet Masks – Your Turn! Host Addresses in binary (net) (SM) (broadcast) (net) (SM) (broadcast)

46 Subnet Masks – Your Turn! Host Addresses in binary (net) (SM) (broadcast)

47 Subnet Masks – Your Turn! Host Addresses in binary (net) /24(SM) (broadcast) (net) /16 (SM) (broadcast)

48 Subnet Masks – Your Turn! Host Addresses in binary (net) /16 (SM) (broadcast)

49 Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries Network Address Subnet Mask

50 Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries What is the range of host addresses in dotted- decimal and binary? What is the broadcast address? How many host addresses?

51 Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries … …

52 Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries … (broadcast) Number of hosts: 2 12 – 2 = 4,096 – 2 = 4,094 hosts

53 Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries … (broadcast)

54 Subnet Masks: Non-Natural Boundaries Subnet masks do not have to end on natural octet boundaries … (broadcast) Number of hosts: 2 5 – 2 = 32 – 2 = 30 hosts

55 Subnets and Subnet Masks Formalized in 1985, the subnet mask breaks a single network in to smaller pieces. A “1” bit in the subnet mask means that the corresponding bit in the IP address should be read as a network number A “0” bit in the subnet mask means that the corresponding bit in the IP address should be read as a host bit. Allows network administrators to divide their network into small networks or subnets. Advantages will be discussed later.

56 What is subnetting? Subnetting is the process of borrowing bits from the HOST bits, in order to divide the larger network into small subnets. Subnetting does NOT give you more hosts, but actually costs you hosts. You lose two host IP Addresses for each subnet, one for the subnet IP address and one for the subnet broadcast IP address. You lose the last subnet and all of it’s hosts’ IP addresses as the broadcast for that subnet is the same as the broadcast for the network. In older technology, you would have lost the first subnet, as the subnet IP address is the same as the network IP address. (This subnet can be used in most networks.) Network Host Network SubnetHost

57 Analogy Before subnetting: In any network (or subnet) we can not use all the IP addresses for host addresses. We lose two addresses for every network or subnet. 1. Network Address - One address is reserved to that of the network. For Example: /16 2. Broadcast Address – One address is reserved to address all hosts in that network or subnet. For Example: This gives us a total of 65,534 usable hosts 100 apples = 98 Usable Apples 65,534 Apples (65,536 – 2)

58 Analogy It is the same as taking a barrel of 100 apples and dividing it into 10 barrels of 10 apples each barrels x 10 apples = 100 apples 98 Apples (100 – 2)

59 However, in subnetting we will see that we lose two apples per subnet, one for the network address and one for the broadcast address. We also lose the entire last basket of apples, subnet, as it contains the broadcast address for the entire network. In older networks, we also lost the first basket, subnet, as it contained the address of the entire network, but this is usually no longer the case. X (less 2) X 9 barrels x 8 apples = 72 apples 98 Apples (100 – 2) 2 = 1 network address + 1 broadcast address

60 Subnet Example Network address “Major Network” Subnet Mask or /16 Applying a mask which is larger than the major network subnet mask, will divide your network into subnets. Major network mask is or /16 Subnet mask used here is or /24 Major Network Subnet Mask: or /16 Subnet Mask: or / Network SubnetHost Network Host

61 Subnet Example Network SubnetHost Network address with /16 Major Network Mask Host172161Host172162Host Using Subnets: Subnet Mask or / Host17216Etc.Host Host Host 255 Subnets Cannot use last subnet as it contains broadcast address Subnets

62 Subnet Example Network SubnetHosts Etc Host Each subnet has 254 hosts, 2 8 – Hosts per Subnet Network address with /16 Major Network Mask Using Subnets: Subnet Mask or /24

63 With NO subnetting: NetworkFirst HostLast Host Broadcast ,534 host addresses, one for network address and one for broadcast address. Subnet Example

64 With subnetting: NetworkFirst HostLast Host Broadcast …

65 With subnetting: NetworkFirst HostLast HostBroadcastHosts … ,770 Total address = 65,536 – 256 (last subnet) = 65,280 = 65,280 – 510 (2 hosts per other 255 subnets) = 64,770

66 With subnetting: NetworkFirst HostLast Host Broadcast Major Network Address: Major Network Mask: Major Network Broadcast Address: Subnet Mask: First Subnet (This is typically used): Subnet Address: Subnet Broadcast Address: Last Subnet (This is typical not used): Subnet Address: Subnet Broadcast Address: