IP Address

1
IP Address

• Computer Network System
• Sirak Kaewjamnong

2
Three Level of Address

• Host name
• ratree.psu.ac.th
• Internet IP address
• 192.168.100.3
• (32 bits address with dot-decimal notation)
• Station address Hardware address assigned to
  network interface card, refer to MAC address or
  Ethernet Address (48 bits)
• 005cf03b004a

3
Converting Host Name to MAC Address

• cs05.cs.psu.ac.th
• 172.28.80.96
• 0050ba499db9

• Resolve IP address by Domain Name System(DNS)
• Resolve MAC address by Address Resolution
  Protocol(ARP)

4
IP Address with Router

• IP address associated with interface (not
  machine)
• Each interface has its own IP address
• Machine with more than one interface called
  multi-home
• Router is multi-homed machine
• Multi-homed not to be router

172.28.80.15
172.28.80.16
172.28.85.116
172.28.85.120
172.28.85.1
172.28.80.1
192.168.99.39
Internet
192.168.98.11
192.168.100.3
192.168.100.4
192.168.100.1
5
Addressing Concept

• Partitions address into 2 fields
• network address
• node address

6
IP Address
7
IP Address Class

• 32 bits address length, contain 2 parts
• Network identifier
• Host identifier

8
IP Address Class
Initial bits
Bit net
range
address spaces
Class
Bit host
usable

• A 0 7 24 0.0.0.0
  -127.255.255.255 224 16,677,214
• B 10 14 16 128.0.0.0
  -191.255.255.255 216 65,534
• C 110 21 8 192.0.0.0
  -223.255.255.255 28 254
• D 1110 28 - 224.0.0.0-239.255.25
  5.255
• E 11110 27 - 240.0.0.0-247.255.255.
  255

9
Special Address

• Host ID all 0s is reserved to refer to network
  number
• 192.168.100.0, 158.108.0.0, 18.0.0.0
• Host ID all 1s is reserved to broadcast to all
  hosts on a specific network
• 192.168.100.255, 158.108.255.255, 18.255.255.255
• Address 0.0.0.0 means default route
• Address 127.0.0.0 means this node (local
  loopback). Message sent to this address will
  never leave the local host
• Address 255.255.255.255 is reserve to broadcast
  to every host on the local network (limited
  broadcast)

10
Problem with Class Assignment

• Class A takes 50 range
• Class B takes 25 range
• Class C take 12.5 range
• These leads to
• address wasteful (specially in class A)
• running out of IP address

11
How to assigns IP Address (RFC 1466)

• Class A no allocations will be made at this
  time
• Class B allocations will be restricted. To
  apply
• organization presents a subnetting more than32
  subnets
• organization more than 4096 hosts
• class C divided into allocated block to
  distributed reginal

12
Class C Assignment

• Assignment is based on the subscriber s 24 month
  projection according to the criteria
• 1. Requires fewer than 256 addresses 1 class C
  network
• 2. Requires fewer than 512 addresses 2
  contiguous class C networks
• 3. Requires fewer than 1024 addresses 4
  contiguous class C networks
• 4. Requires fewer than 2048 addresses 8
  contiguous class C networks
• 5. Requires fewer than 4096 addresses 16
  contiguous class C networks
• 6. Requires fewer than 8192 addresses 32
  contiguous class C networks
• 7. Requires fewer than 16384 addresses 64
  contiguous class C networks

13
Problem with Large Network

• Class B Flat Network more than 60,000 hosts
• How to manage?
• Performance?

14
Problem with Large Network

• Class B subdivided network to smaller group
  with router

15
Subnetwork Benefits

• Increase the network managers control the
  address space
• Easy to allocate the address space
• Better network performance
• Hide routing structure from remote routers, thus
  reducing routes in their routing tables
• Subdivide on IP network number is an important
  initial task of network managers

16
How to assign subnet

• Divide host ID into 2 pieces
• Class B address such as 150.0 might use its third
  byte to identify subnet
• subnet1 150.0.1.X X host address range
  from 1-254
• subnet2 150.0.200.X

17
Subnet Mask

• 32 bit number, tell router to recognize the
  subnet field, call subnet mask
• subnet rule The bit covering the network and
  subnet part of address are set to 1
• Example class B with 24 bits mask
• 1111 1111 1111 1111 1111 1111 0000
  0000
• subnet mask 255.255.255.0
• zero bit are used to mask out the host number
  resulting the network address

18
Subnet Mask

• Subnet mask 255.255.255.0 for class B tells
• network has been partition to 254 subnets
• 150.10.1.X to 150.10.254.X
• logic and between IP address with mask yields
  network address
• 150.10.1.55 150.10.240.243
• and and
• 255.255.255.0 255.255.255.0
• 150.10.0.0 150.10.0.0 same network address

19
Subnet Mask Bits

• Use contiguous subnet mask
• 128 64 32 16 8 4 2 1
• 1 0 0 0 0 0 0 0
  128
• 1 1 0 0 0 0 0 0
  192
• 1 1 1 0 0 0 0 0
  224
• 1 1 1 1 0 0 0 0
  240
• 1 1 1 1 1 0 0 0
  248
• 1 1 1 1 1 1 0 0
  252
• 1 1 1 1 1 1 1 0
  254
• 1 1 1 1 1 1 1 1
  255

20
Subnet Class B Example

• 255.255.0.0 (0000 0000 0000 0000)
• 0 subnet with 65534 hosts (default subnet)
• 255.255.192.0 (1100 0000 0000 0000)
• 2 subnets with 16382 hosts
• 255.255.252.0 (1111 1100 0000 0000)
• 62 subnets with 1022 hosts
• 255.255.255.0 (1111 1111 0000 0000)
• 254 subnets with 254 hosts
• 255.255.255.252 (1111 1111 1111 11000)
• 16382 subnets with 2 hosts

21
Subnet Class C Example

• 255.255.255.0 ( 0000 0000)
• 0 subnets with 254 hosts (default subnet)
• 255.255.255.192 (1100 0000)
• 2 subnets with 62 hosts
• 255.255.255.224 (1110 0000)
• 6 subnets with 30 hosts
• 255.255.255.240 (1111 0000)
• 14 subnets with 14 hosts

22
Subnet Interpretation

• IP Address Subnet mask Interpretation
• 158.108.2.71 255.255.255.0 host 71 on subnet
  158.108.2.0
• 150.10.25.3 255.255.255.192 host 3 on subnet
  150.10.25.0
• 130.122.34.132 255.255255.192 host 4 on subnet
  130.122.34.128
• 200.190.155.66 255.255.255.192 host 2 on
  subnet 200.190.155.64
• 18.20.15.2 255.255.0.0 host 15.2 on subnet
  18.20.0.0

23
Class B Subnet with Router

• Router is used to separate network

Picture from Kasetsart University
24
Subnet Routing

• Traffic is route to a host by looking bit wise
  AND results
• if dest IP addr subnet mask my IP addr
  subnet mask
• send packet on local network dest IP addr is
  on the same subnet
• else
• send packet to router dest IP address is on
  difference subnet

25
Type of Subnet

• Static subnet all subnets in the subnetted
  network use the same subnet mask
• pros simply to implement, easy to maintain
• cons wasted address space (consider a network of
  4 hosts with 255.255.255.0 wastes 250 IPs)
• Variable Length Subnet the subnets may use
  difference subnet masks
• pros utilize address space
• cons required well managment

26
Variable Length Subnet Mask

• General idea of VLSM
• A small subnet with only a few hosts needs a
  subnet mask that accommodate only few hosts
• A subnet with many hosts need a subnet mask to
  accomdate the large number of hosts
• Network Managers responsibility to design and
  appropriate VLSM

27
VLSM Sample Case
Picture from Kasetsart university