Instructor: Sam Nanavaty DNS and IP addressing

Instructor: Sam Nanavaty How does a router know where to route the information when you simply type in a URL (e.g., in the Internet browser?

Instructor: Sam Nanavaty

What is an IP address?

Instructor: Sam Nanavaty IP addressing 32 bits in length 4 octets Five classes A,B,C,D and E Only A,B and C used for naming devices. D used for multicasting groups E is reserved for experimental purposes

Instructor: Sam Nanavaty ClassFormatDefault Network Prefix High Order Bits Usable Network Address range AN.H.H.H Hosts:16.7 m Mask: bits – Loopback BN.N.H.H Hosts:65,534 Mask: bits – CN.N.N.H Hosts: bits – # of hosts = 2 n -2 (where n = # of bits in host Id) Why? Host ID = all 1’s is not permitted as this refers to broadcast address Host Id = all 0’s is not permitted as this refers to “this network”

Instructor: Sam Nanavaty Examples Identify Network address, class, and determine if it is valid host address as well

Instructor: Sam Nanavaty Subnetting Steal the bits from the host portion of the IP address and add it to the network portion (gives more networks and fewer hosts per network) Can you think of the benefits of subnetting?

Instructor: Sam Nanavaty Subnet mask determination Convert IP addr and default mask in to binary Identify your base network addr Determine how many bits are needed to achieve desired number of subnets and extend the 1’s in the subnet mask by this amount Now you know subnet portion and the host portion of the IP address. Make sure that the said mask still provides enough hosts per subnet (including some room for growth)

Instructor: Sam Nanavaty Masking rule Mask always is assigned from left to right in the bit order Every mask contains contiguous 1’s –i.e., is correct, however, is incorrect Hosts on the same network, must use the same subnet mask Subnets that are all 0’s or all 1’s are NOT allowed by default (in private environment you may use these however)

Instructor: Sam Nanavaty Subnet mask determination IP addressReqd HostsReqd Subnets As many as possible 16

Instructor: Sam Nanavaty IP addressReqd HostsReqd Subnets Mask = Yields 4 -2 = 2 subnets As many as possible Any mask > 21 bits will work, however, 21 bits yields most hosts 248 = Yields 32-2 = 30 subnets Answers

Instructor: Sam Nanavaty Calculating the range of addresses given a subnet mask IP Network address : Subnet Mask: (248 = ) This yields up to 30 subnets (2 5 -2) with up to 6 hosts (2 3 -2) per subnet – Discard as Subnet Id = 0! ( – ) – ( – ) (discard 1 st and last IP addr as host Id cannot be all 0’s or 1’s) – ( ) (discard 1 st and last IP addr) – ( – ) (discard 1st and last IP addr) – (discard subnet Id = all 1’s) Remove first and last subnets as well as first and last IP addresses for each subnet The final valid range of addresses are as follows: – – – ( – )

Instructor: Sam Nanavaty Practice example IP address : Subnet Mask: This yields up to ________ subnets with up to _____ hosts per subnet Now calculate the range of addresses for this subnet mask Next determine the valid IP addresses in this range

Instructor: Sam Nanavaty IP Network address : Subnet Mask: (224 = ) This yields up to 6 subnets with up to 30 hosts per subnet Range : – ( – ) (discard as subnet ID =0) – ( ) (discard addr w/ host =0 and 255) – ( ) (discard addr w/ host =0 and 255) – ( ) (discard addr w/ host =0 and 255) – ( ) (discard addr w/ host =0 and 255) – ( ) (discard addr w/ host =0 and 255) – ( ) (discard addr w/ host =0 and 255) – ( ) (discard as subnet ID = 255)

Instructor: Sam Nanavaty Address Mask A = (D & M) Where: A = 32 bit IP address M = 32 bit address mask D = Destination address

Instructor: Sam Nanavaty CIDR Notation /16 The number after the / indicates the number of 1’s in the subnet mask. Used to partition addresses: /16 ISP /28 Network A ( ) /28 Network B IP reserves host address zero (denotes network) IP reserves host address all 1’s for broadcast) IP reserves network prefix 127/8 for loopback

Instructor: Sam Nanavaty /22 Which subnet does this address belong to?

Instructor: Sam Nanavaty /28 Find the subnet this address belongs to.

Instructor: Sam Nanavaty If you are using a subnet mask of , can the following IP address be assigned to a host using the given subnet mask

Instructor: Sam Nanavaty ISP / /24 Identify the valid IP address assignment for the workstation DG DG DG

Instructor: Sam Nanavaty