Addressing & Subnetting

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1 Addressing & Subnetting

2 Addressing to identify and locate each host. We call it addressing. Identification: hostname, address (MAC, IP) IP add? MAC add? MAC add: local IP add: internetwork An address generally represents the connection to the network

3 Addressing unique address: letter (network address) and number (host address)

4 IP Address (IPv4) IP address is 32-bit long. It is often writen in dotted decimal format.

5 Addressing IP add has two parts: net-id & host-id Two different networks must have different network address (net-id). Two different hosts in the same network must have different host address (host-id). Hosts in the same network have the same network address. Broadcast domain: one network add Network address= IP address AND Subnet mask

Example 1: SM : 255.255.255.0 Net/host id: N.N.N.H Net E1 (Net-ID): 192.

6 Example 1: SM : Net/host id: N.N.N.H Net E1 (Net-ID): Net E2 : Net E3 : Number broadcast domain?

7 Example 2: SM: Net add: Net/host id: N.N.N.H H: hhhhhhhh

8 Example 3: IP add: Subnet mask: Net add: Net/Host ID: N.N.N.H IP add : SM : Net add :

9 Example 4: IP add: Subnet mask: Net add:? IP add : SM : Net add : Note: subnetmask

10 Hierachical addressing scheme As a hierachical addressing scheme, IP addresses are divided into classes.

11 Classes of IP Addresses Class A addresses are assigned to larger networks. Class B addresses are used for mediumsized networks Class C for small networks.

Classes of IP Addresses First octet order bits: Class A: 00000000 (0) 00000001 (1) 01111110 (126) 01111111 (127) First octet order bits: Class B: 10000000 (128) 10000001 (129) 10111110 (190)

12 Classes of IP Addresses First octet order bits: Class A: (0) (1) (126) (127) First octet order bits: Class B: (128) (129) (190) (191) First octet order bits: Class C: (192) (193) (222) (223) First octet order bits: Class D: (224) (225) (238) (239)

13 Classes of IP Addresses

14 Network Address When all host-bits are zeros (0), we have a number that represents network address. This address is reserved, namely it cannot be assigned to any host.

15 Broadcast Address When host-bits are all one (1), we have a number that represents broadcast address. This address is also reserved, namely it cannot be assigned to any host. Exp: ping

16 Reference: broadcast Address The router supports the following kinds of broadcast types: Limited broadcast - A packet is sent to a specific network or series of networks. In a limited broadcast packet destined for a local network, the network identifier portion and host identifier portion of the destination address is either all ones ( ) or all zeros ( ). Flooded broadcast - A packet is sent to every network. Directed broadcast - A packet is sent to a specific destination address where only the host portion of the IP address is either all ones or all zeros (such as or ).

17 Unicast and Broadcast Transmission Unicast transmission Broadcast transmission The concept of unicast and broadcast transmission exist in both layer 2 and layer 3 protocols. There are refelections in the addressing scheme.

Reserved IP Address Host-bits = all zeros (network address); exp: 176.10.0.0 Host-bits = all ones (broadcast address); exp: 176.10.255.

18 Reserved IP Address Host-bits = all zeros (network address); exp: Host-bits = all ones (broadcast address); exp: Network-bits = all ones; exp: x.x.x Network-bits = all zeros; exp: x.x.x 127.x.x.x (loopback address = ).

19 Reference: Reserved IP Address all 0s -This host, exp: all 0s.host - Host on this net, exp:0.x.x.x all 1s - Limitted broadcast (local net),exp: Net.all 1s - Directed broadcast for net, exp: anything (often 1) - Loopback, ( ) Exp: ping

20 Public IP Addresses Public IP addresses are unique. No two machines that connect to a public network can have the same IP address. (X#Y#Z ) Public IP addresses must be obtained from an Internet service provider (ISP) or a registry at some expense. With the rapid growth of the Internet, public IP addresses were beginning to run out (IP address depletion). New addressing schemes, such as classless interdomain routing (CIDR) and IPv6 were developed to help solve the problem. Private IP addresses are another solution.

21 Private IP Addresses

22 Private IP Addresses RFC 1918 sets aside three blocks of IP addresses for private, internal use. These three blocks consist of one Class A, a range of Class B addresses, and a range of Class C addresses. Addresses that fall within these ranges are not routed on the Internet backbone. Internet routers immediately discard private addresses.

Using Private Addresses When addressing a nonpublic intranet, a test lab, or a home network, we normally use private addresses instead of globally unique addresses.

23 Using Private Addresses When addressing a nonpublic intranet, a test lab, or a home network, we normally use private addresses instead of globally unique addresses. Private addresses can be used to address point-to-point serial links without wasting real IP addresses. Connecting a network using private addresses to the Internet requires translation of the private addresses to public addresses. This translation process is referred to as Network Address Translation (NAT).

24 Subnetting Net 1: Net 2: Net 3: Net 4: Hosts per network (usable): 2^16-2= 65534!!! IP add for poin-to-point link (router router): 2 hosts 2 IP add Waste!!! Exp: Net add: ; SM: ; Number hosts usable: 2^8-2=254 If hosts per network is 60 used: 6 bits host: xxhhhhhh, 2^6-2=62 hosts; unused: 2 bits host xxhhhhhh xx (0) xx xx xx xx (63)

25 Subnetting Subnetting is another method of managing IP addresses. This method of dividing full network address classes into smaller pieces has prevented complete IP address exhaustion. The network is no longer limited to the default Class A, B, or C network masks and there is more flexibility in the network design. Subnet addresses include the network (N) portion, plus a subnet (sn) field and a host (H) field. To create a subnet address, a network administrator borrows bits from the host field and designates them as the subnet field.

26 Subnetting Host bit must be reassigned as network bit.the starting borrow bit is the leftmost hosting bit. Providing broadcast contentment and low level security.

27 Subnetting 1 net add: ; SM: ; 254 hosts hosts per network: 30; networks: 6? Borrows bits: 3 2^3-2= 6 subnets Host bits: 5 2^5-2=30 hosts SM: Subnets: Exp: xxxhhhhh 000 (0) 001 (32) 010 (64) 011 (96) 100 (128) 101 (160) 110 (192) 111 (224)

The subnet mask: using binary ones in the host octet(s) (2 power of

28 Establishing SM address The number of bits in the subnet will depend on the maximum number of hosts required per subnet. The subnet mask: using binary ones in the host octet(s) (2 power of borrowed bits ) 2 = usable subnets (2 power of remaining host bits ) 2= usable hosts

Applying the Subnet Mask Exp: subnet 192.168.10.32/27 Host Range??? 192.168.10.001hhhhh.

29 Applying the Subnet Mask Exp: subnet /27 Host Range??? hhhhh (33) (62)

30 Example 5: Primary network /24 Hosts per network: 30 Number subnets: 4 Borrows bits? Subnets? IP add for hosts?

IP Addressing and Subnetting

IP Addressing and Subnetting Internet Layer The purpose of the Internet layer is to send packets from a network node and have them arrive at the destination node independent of the path taken. Internet