Transcript IP Address
IP Address
Computer Network System
Sirak Kaewjamnong
1
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)
– 00:5c:f0:3b:00:4a
2
Converting Host Name to MAC Address
cs05.cs.psu.ac.th
172.28.80.96
00:50:ba:49:9d:b9
Resolve IP address by
Domain Name
System(DNS)
Resolve MAC address by
Address Resolution
Protocol(ARP)
3
IP Address with Router
IP address associated with
172.28.80.15 172.28.80.16
172.28.85.116 172.28.85.120
interface (not machine)
• Each interface has its own IP
address
172.28.85.1
• Machine with more than one
172.28.80.1
192.168.99.39
interface called multi-home
Internet
• Router is multi-homed machine
192.168.98.11
• Multi-homed not to be router 192.168.100.4 192.168.100.3
192.168.100.1
4
Addressing Concept
• Partitions address into 2 fields
* network address
* node address
5
IP Address
32 bits
8,16,24 bits
Network
Host
32 bits
8 bits
8 bits
8 bits
172
28
80
10101100 00011100 01010000
.
.
.
8 bits
96
01100000
6
IP Address Class
32 bits address length, contain 2 parts
• Network identifier
• Host identifier
8
16
Class A 0 Network ID
Class B 10
Class C 110
Class D 1110
Class E 11110
24
32
Host ID
Network ID
Host ID
Network ID
Host ID
Multicast Address
Unused
7
IP Address Class
Initial
Bit
Bit
Class bits net host
A
B
C
D
E
0
10
110
1110
11110
7
14
21
28
27
24
16
8
-
range
address
spaces
usable
0.0.0.0 -127.255.255.255 224 16,677,214
128.0.0.0 -191.255.255.255 216 65,534
192.0.0.0 -223.255.255.255 28 254
224.0.0.0-239.255.255.255
240.0.0.0-247.255.255.255
8
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)
9
Problem with Class Assignment
• Class A takes 50 % range
• Class B takes 25 % range
• Class C take 12.5 % range
Class A
Class B
These leads to:
• address wasteful (specially in class A)
• running out of IP address
E
D
C
10
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
11
Class C Assignment
• Assignment is based on the subscriber ‘s 24 month projection
according to the criteria:
1.
2.
3.
4.
5.
6.
7.
Requires fewer than 256 addresses : 1 class C network
Requires fewer than 512 addresses : 2 contiguous class C networks
Requires fewer than 1024 addresses : 4 contiguous class C networks
Requires fewer than 2048 addresses : 8 contiguous class C networks
Requires fewer than 4096 addresses : 16 contiguous class C networks
Requires fewer than 8192 addresses : 32 contiguous class C networks
Requires fewer than 16384 addresses : 64 contiguous class C networks
12
Problem with Large Network
• Class B “Flat Network” more than 60,000 hosts
– How to manage?
– Performance?
150.0.0.1 150.0.0.2
...
150.0.255.254
13
Problem with Large Network
• Class B “subdivided network” to smaller group with
router
150.0.1.1
150.0.40.1 150.0.40.2
150.0.1.2
150.0.10.1 150.0.10.2
Router
150.0.200.1 150.0.200.2
14
Subnetwork Benefits
•
•
•
•
Increase the network manager’s 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
15
How to assign subnet
• Divide host ID into 2 pieces
host ID
Network ID Subnet address Host address
Choose
appropriate
size
• 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
16
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
17
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
18
Subnet Mask Bits
Use contiguous subnet mask
128
1
1
1
1
1
1
1
1
64
0
1
1
1
1
1
1
1
32
0
0
1
1
1
1
1
1
16
0
0
0
1
1
1
1
1
8
0
0
0
0
1
1
1
1
4
0
0
0
0
0
1
1
1
2
0
0
0
0
0
0
1
1
1
0
0
0
0
0
0
0
1
= 128
= 192
= 224
= 240
= 248
= 252
= 254
= 255
19
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
20
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
21
Subnet Interpretation
IP Address
158.108.2.71
150.10.25.3
130.122.34.132
200.190.155.66
18.20.15.2
Subnet mask
255.255.255.0
255.255.255.192
255.255255.192
255.255.255.192
255.255.0.0
Interpretation
host 71 on subnet 158.108.2.0
host 3 on subnet 150.10.25.0
host 4 on subnet 130.122.34.128
host 2 on subnet 200.190.155.64
host 15.2 on subnet 18.20.0.0
22
Class B Subnet with Router
Router is used to separate network
Picture from Kasetsart University
23
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}
24
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
25
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 Manager’s responsibility to design and
appropriate VLSM
26
VLSM Sample Case
Picture from Kasetsart university
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