Public and Private IP AddressesNo two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized.
Procedure was needed to make sure that addresses were in fact unique.
Originally, an organization known as the Internet Network Information Center (InterNIC) handled this procedure. InterNIC no longer exists and has been succeeded by the Internet Assigned Numbers Authority (IANA).
IANA carefully manages the remaining supply of
CSE401N:Computer Networks Lecture 11+12+13
The Internet Protocol(IP)
IPv4 & IPv6
CIDR, Subnet & NAT
DHCP,ARP
The Internet Network layer
routing
table Routing protocols
path selection
RIP, OSPF, BGP IP protocol
addressing conventions
datagram format
packet handling conventions ICMP protocol
error reporting
router “signaling” Transport layer: TCP, UDP Link layer physical layer Network
layer Host, router network layer functions:
IP Addressing: introduction
223.1.1.1 223.1.1.2 223.1.1.3 223.1.1.4 223.1.2.9 223.1.2.2 223.1.2.1 223.1.3.2 223.1.3.1 223.1.3.27 223.1.1.1 = 11011111 00000001 00000001 00000001 223 1 1 1 IP address: 32-bit identifier for host, router interface
interface: connection between host, router and physical link
router’s typically have multiple interfaces
host may have multiple interfaces
IP addresses associated with interface, not host, router
IP Addressing
223.1.1.1 223.1.1.2 223.1.1.3 223.1.1.4 223.1.2.9 223.1.2.2 223.1.2.1 223.1.3.2 223.1.3.1 223.1.3.27 network consisting of 3 IP networks
(for IP addresses starting with 223,
first 24 bits are network address) LAN IP address:
network part (high order bits)
host part (low order bits)
What’s a network ? (from IP address perspective)
device interfaces with same network part of IP address
can physically reach each other without intervening router
IP Addressing
223.1.1.1 223.1.1.3 223.1.1.4 223.1.2.2 223.1.2.1 223.1.2.6 223.1.3.2 223.1.3.1 223.1.3.27 223.1.1.2 223.1.7.0 223.1.7.1 223.1.8.0 223.1.8.1 223.1.9.1 223.1.9.2 Interconnected
system consisting
of six networks How to find the networks?
Detach each interface from router, host
create “islands of isolated networks
IP Addresses
0 network host 10 network host 110 network host 1110 multicast address A B C D class 1.0.0.0 to
127.255.255.255 128.0.0.0 to
191.255.255.255 192.0.0.0 to
223.255.255.255 224.0.0.0 to
239.255.255.255 32 bits “class-full” addressing: given notion of “network”, let’s re-examine IP addresses:
IP Addressing
An IP address is a 32-bit sequence of 1s and 0s.
To make the IP address easier to use, the address is usually written as four decimal numbers separated by periods.
This way of writing the address is called the dotted decimal format.
Decimal and Binary Conversion
IPv4 Addressing
Class A, B, C, D, and E IP Addresses
Reserved IP Addresses
Certain host addresses are reserved and cannot be assigned to devices on a network.
An IP address that has binary 0s in all host bit positions is reserved for the network address.
An IP address that has binary 1s in all host bit positions is reserved for the broadcast address.
Network Address
Broadcast Address
Public and Private IP Addresses
No two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized.
Procedure was needed to make sure that addresses were in fact unique.
Originally, an organization known as the Internet Network Information Center (InterNIC) handled this procedure. InterNIC no longer exists and has been succeeded by the Internet Assigned Numbers Authority (IANA).
IANA carefully manages the remaining supply of IP addresses to ensure that duplication of publicly used addresses does not occur.
However, private networks that are not connected to the Internet may use any host addresses, as long as each host within the private network is unique.
Public and Private IP Addresses
RFC 1918 sets aside three blocks of IP addresses for private, internal use.
Addresses that fall in these ranges are not routed on the Internet backbone. Internet router immediately discard private addresses.
Connecting a network using private addresses to the Internet requires translation of the private addresses to public addresses using Network Address Translation (NAT).
IP addressing: CIDR
11001000 00010111 00010000 00000000 network
part host
part 200.23.16.0/23 Classful addressing:
inefficient use of address space, address space exhaustion
e.g., class B net allocated enough addresses for 65K hosts, even if only 2K hosts in that network
CIDR: Classless InterDomain Routing
network portion of address of arbitrary length
address format: a.b.c.d/x, where x is # bits in network portion of address
Why Subnet? Millions of Addresses Available
Over 16,000,000
Efficiency
Non-subnetted networks are wasteful
Division of networks not optimal
Smaller Network
Easier to manage
Smaller broadcast domains
So Make the network as small as possible
Divide the network into subnetworks
Borrow some bits from the host add.
What You Need
Understand Address System
Understand Classes of Networks
“Two-Tums” Table
Formulas
Magic Numbers
Subnet Mask
“ANDing” Process
Dissecting the Address > Classes <
_ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _
1 0 0 0 0 0 0 0 .0 0 0 1 0 0 0 0 .0 0 1 0 0 0 0 0. 0 0 0 0 1 1 0 1 (Digital)
128 . 16 . 32 . 13 (Decimal)
CLASS
B CLASS RANGES:
A: 0 – 127 N . H . H . H
B: 128 – 191 N . N . H . H
C: 192 – 223 N . N . N . H
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