Switching and Routing BCS/BS Elective Spring 2012

Transcription

1 Switching and Routing BCS/BS Elective Spring 2012 Dr. Husnain Mansoor Ali Lecture 4,5 and 6 18 th, 23 rd and 25 th January 2012 SZABIST

2 Today's Lecture Internet layer Protocols ARP RARP IP Addressing Subnetting basics How to create subnets Subnet masks and CIDR Class C subnetting Class B subnetting

3 Internet Layer Protocols Internet Protocol (IP) (RFC 791) Internet Control Message Protocol (ICMP) Address Resolution Protocol (ARP) Reverse Address Resolution Protocol (RARP)

4 ARP finds hardware address of a host from a known IP address

5 ARP Header example Ethernet Header Destination: FF:FF:FF:FF:FF:FF Ethernet Broadcast Source: 00:A0:24:48:60:A5 Protocol Type: 0x0806 IP ARP ARP - Address Resolution Protocol Hardware: 1 Ethernet (10Mb) Protocol: 0x0800 IP Hardware Address Length: 6 Protocol Address Length: 4 Operation: 1 ARP Request Sender Hardware Address: 00:A0:24:48:60:A5 Sender Internet Address: Target Hardware Address: 00:00:00:00:00:00 (ignored) Target Internet Address: Extra bytes (Padding):... 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A Frame Check Sequence: 0x

6 RARP

7 IP Addressing An IP address is a numeric identifier assigned to each machine on an IP network It designates the specific location of a device on the network IP addressing was designed to allow hosts on one network to communicate with a host on a different network regardless of the type of LANs the hosts are participating in

8 IP Terminology BIT: A bit is one digit, either a 1 or a 0. BYTE: A byte is 7 or 8 bits, depending on whether parity is used. For the rest of this chapter, always assume a byte is 8 bits. OCTET: An octet, made up of 8 bits, is just an ordinary 8-bit binary number. In this chapter, the terms byte and octet are completely interchangeable. Network address: This is the designation used in routing to send packets to a remote network for example, , , and Broadcast address: The address used by applications and hosts to send information to all nodes on a network is called the broadcast address.

9 Network Addressing Subdividing an IP address into a network and node address is determined by the class designation of one s network. This figure summarizes the three classes of networks

10 Reserved Addressing Address Network address of all 0s Network address of all 1s Network Node address of all 0s Node address of all 1s Entire IP address set to all 0s Entire IP address set to all 1s Function Interpreted to mean this network or segment. Interpreted to mean all networks. Reserved for loopback tests. Interpreted to mean network address or any host on specified network. Interpreted to mean all nodes on the specified network Used by Cisco routers to designate the default route. Could also mean any network. (same as Broadcast to all nodes on the current network; ) sometimes called an all 1s broadcast or limited broadcast

11 Private Addressing Address Class Class A Class B Class C Reserved Address Space through through through

12 IP Address Demonstration Class A Class B Class C Network Network Network Host Host

13 Subnetting Basics Benefits of subnetting include: Reduced network traffic Optimized network performance Simplified management Facilitated spanning of large geographical distances.

14 Subnet Masks Used to define which part of the host address will be used as the subnet address A 32-bit value that allows the recipient of IP packets to distinguish the network ID portion of the IP address from the host ID portion

15 Default Subnet Masks

16 How To Create Subnets Take bits from the host portion of the IP address and reserve them to define the subnet address

17 Classless Inter-Domain Routing (CIDR) Used to allocate an amount of IP address space to a given entity (company, home, customer, etc). Example: /28 The slash notation (/) means how many bits are turned on (1s) and tells you what your subnet mask is

18 CIDR Values

19 Subnetting Class C Addresses In a Class C address, only 8 bits are available for defining the hosts. Remember that subnet bits start at the left and go to the right, without skipping bits. This means that the only Class C subnet masks can be the following: Binary Decimal CIDR = 128 / = 192 / = 224 / = 240 / = 248 / = 252 /30

20 Subnetting Class C Addresses

21 How Many Subnets? 2 x = number of subnets. X is the number of masked bits, or the 1s. For example, in , the number of ones gives us 2 2 subnets. In this example there are 4 subnets.

22 How Many Hosts Per Subnet? 2 y -2 = number of hosts per subnet. Y is the number of unmasked bits, or the 0s. For example, in , the number of zeros gives us hosts. In this example, there are 62 hosts per subnet.

23 What Are The Valid Subnets? 256-subnet mask = block size, or base number. For example = is the first subnet. The next subnet would be the base number plus itself or 64+64=128, (the second subnet).

24 What s The Broadcast Address For Each Subnet? The broadcast address is all host bits turned on, which is the number immediately preceding the next subnet

25 What Are The Valid Hosts? Valid hosts are the number between the subnets, omitting all 0s and all 1s.