RIR : Representative of ISP
Establishment of the
Number Resource Organisation
A regional Internet registry (RIR) is an organization overseeing
the allocation and registration of Internet Number resources
within a particular region of the world. Resources include IP
There are currently five RIRs in operation:
American Registry for Internet Numbers (ARIN) for North
America and parts of the Caribbean
RIPE Network Coordination Centre (RIPE NCC) for Europe, the
Middle East and Central Asia
Asia-Pacific Network Information Centre (APNIC) for Asia and
the Pacific region
Latin American and Caribbean Internet Addresses Registry
(LACNIC) for Latin America and parts of the Caribbean region
African Network Information Centre (AfriNIC) for Africa
Address consists of 32 Bits
Represented in A.B.C.D where A represent
Decimal Value of 8 Bits or 1 Byte
A range from 0-255.
Few Examples of Binary conversions
Binary to Decimal
Decimal to Binary
◦ One to One Communication
◦ One to Many Communication
◦ One to All Communication
D Class (Reserve for Multicasting)
E Class (Reserve for Scientific Research)
◦ Network Bits
Common among all the users on same Network
◦ Host Bits
Unique Bits to Identify the Host on the LAN segment
Network – ID
◦ Represent all the Host on the Network
◦ Cannot be assigned to Users
◦ When all the HOSTID portion bits of an IP address are zero’s
then it is called Network Address.
class A 10.0.0.0
class B 172.16.0.0
class C 192.168.10.0
Broadcast – ID
◦ Address to send Packet to all the Host on the Network
◦ Cannot be assigned to the Users
◦ When all the HOSTID portion bits of an IP address are one’s then it
is called Broadcast Address.
class A 10.255.255.255
class B 172.16.255.255
class C 192.168.10.255
Host – ID
◦ Address assigned to Host on the Network
◦ All Host must have the Unique Host-ID
◦ When all the NETID as well as HOSTID portion bits of an IP address are
0’s then it is used for Default Routing (CISCO Routers)
Loopback Addresses (Self Testing)
APIPA Address(Automatic Private IP Address)
Subnet Mask:- It is used to represent the
Network bits in the IP address.
◦ 1 represent the corresponding bit in IP address is
◦ 0 represent the corresponding bit in IP address is
Subnet Mask Helps to identify the Host in the Given
Class Less Inter domain Range
◦ It is the Decimal representation of the no. of
Network bits in the IP Address
◦ 192.168.0.0 /24
◦ 172.16.0.0 /16
◦ 10.0.0.0 /8
Subnetting:- Is concept to break down the bigger
Network into two or more than two smaller
To identify subnets, you will “borrow” bits from
the host ID portion of the IP address:
The number of subnets available depends on the
number of bits borrowed.
The available number of subnets = 2s, I which s is the
number of bits borrowed.
The number of hosts per subnet available depends
upon the number of host ID bits not borrowed.
The available number of hosts per subnet = 2h -2, in
which h is the number of host bits not borrowed.
One address is reserved as the network address.
One address is reserved as the broadcast address.
Subnetting is based up on NETID portion bits.
In this case we need to borrow some bits from Host ID portion that depends
up on the number of subnets
For e.g 192.168.10.0/26
Step 1: Identify the total number of subnets (how many)?
2n = number of subnets
22 = 4
Where n are the number of borrowed bits from hostId portion.
Step 2: Identify the the total number of hosts for each subnets (how many)?
2m - 2 = number of valid hosts
26 – 2 = 62
Where m are remaining number of bits in hostid portion.
Step 3: Calculate Subnet Mask and Range.
11111111 11111111 11111111 11000000
255 .255 .255 .192
Range:256 - 192 = 64
Step 4: Identify the total number of subnets (Which one)?
Step 5: Identify the valid number of host for each subnet (which one)?
(i) 192.168.10.1 -- 192.168.10.62
(ii) 192.168.10.65 -- 192.168.10.126
(iii)192.168.10.129 -- 192.168.10.190
(iv) 192.168.10.193 -- 192.168.10.254
Step 6:Identify the broadcast address for each subnet?
Subnet a network with a private network
address of 172.16.0.0./16 so that it provides
100 subnets and maximizes the number of host
addresses for each subnet.
◦ How many bits will need to be borrowed?
◦ What is the new subnet mask?
◦ What are the first four subnets?
◦ What are the range of host addresses for the four
Subnetting has limitation of only Splitting the
network into smaller symmetrical networks.
Variable Length Subnet Mask (VLSM)
◦ VLSM Provides the use of Subnetting in more
◦ Allow to splitting the network into smaller
Subnet 172.16.14.0/24 is divided into smaller subnets.
– Subnet with one mask (/27).
– Then further subnet one of the unused /27 subnets into multiple /30 subnets.
Routing protocols can summarize addresses
of several networks into one address.
◦ Classful routing protocols do not include the subnet
mask with the network in the routing advertisement.
◦ Within the same network, consistency of the subnet
masks is assumed, one subnet mask for the entire
◦ Summary routes are exchanged between foreign
◦ Examples of classful routing protocols include:
Note: Classful routing protocols are legacy routing protocols typically
used to address compatibility issues. RIP version 1 and Interior Gateway
Routing Protocol (IGRP) are introduced to provide examples.
Classless routing protocols include the subnet
mask with the network in the advertisement.
Classless routing protocols support VLSM; one
network can have multiple masks.
Summary routes must be manually controlled
within the network.
Examples of classless routing protocols include:
RIPv2, EIGRP, OSPF
RIPv2 and EIGRP act classful by default, and
summary routes are exchanged between foreign
The no auto-summary command forces these
protocols to behave as if they are classless.
22.214.171.124 /32 Host
126.96.36.199 /27 Subnet
188.8.131.52 /24 Network
184.108.40.206 /16 Block of Networks
0.0.0.0 /0 Default
Supports host-specific routes, blocks of networks,
and default routes
Routers use longest prefix match
Classful RIPv1 and IGRP do not advertise subnets,
and therefore cannot support discontiguous subnets.
Classless OSPF, EIGRP, and RIPv2 can advertise subnets,
and therefore can support discontiguous subnets.
◦ Subnetting lets you efficiently allocate addresses by
taking one large broadcast domain and breaking it
up into smaller more manageable broadcast
◦ VLSMs let you more efficiently allocate IP addresses
by adding multiple layers of the addressing
◦ The benefits of route summarization include
smaller routing tables and the ability to isolate