CCNA Part 7: An Introduction to IP Addressing

An Introduction to IP addressing



An IP address is made up of a network portion and host portion. If we use the analogy of a Postal address we can say the network portion is the same as a  postal code, the postal code area contains multiple houses and businesses, the street address points to a specific house or business which is the host portion on a network

In Binary the IP address looks like this:

IP addressing and Classes

Class                     Private IP Range



Class A Networks


The IP range – is using a Class A network. For example the IP address is an example of a class A IP address. So using

In the above screenshot we can see the network portion is 8bit and the host portion is 24bit

Class B networks


Class B Networks has a range from –, in class B addresses the first 2 octets (first 16bits) are the network portion and the next last 2 octets are the host portion. On a class B network you can host about 65000 hosts

Class C Networks


Class C networks have the IP range –, in a class C network the first 3 Octets (first 24 bits) are the network portion the last 4 bits are the host portion. Class C networks were designed for small businesses. In a class C network we have the possibility to create many networks but only a maximum of 255 Host IDs

Class D networks

Class D networks have an IP range from –, it’s a 32bit address and it’s a Multicast address


A example of a multicast address Is a specific address which is used for the protocol OSPF – Open Shortest Path First.  This protocol allows users to connect to this multicast address to stream information from it. So what is it used for exactly? It can be used for streaming companywide a video presentation. A video feed can basically be sent to a server, the server sends a single stream on to the network with a specific multicast address, then what happens all the devices on the network can join into that one stream of traffic using the multicast address. This how Netflix or YouTube works, this is how every user connects to a stream. The multicast stream does not work with Internet; we can only do this with IPv4 on our internal networks. Only a well-seasoned Network engineer would use multicast and its not something a low level Network technician would normally be messing around with.


Classless Addressing

Classless addressing uses something called the subnet mask, the subnet mask is a kind of hack to solve the problem of running out of Classful addresses. The subnet mask is used to determine the network portion and host portion of our network address.

So using the IP address I have converted it to binary as in the shown in the following screenshot. What we do is look at the binary number shaded in light blue, we put all ones in here, and where the shading is orange we put zeros.  Now we can translate the Binary numbers to decimal.

Adding up the bits in the first 3 octets = 255.255.255 and the last octet all zeros = 0


So our subnet mask is which is class C network

Let’s take a look at another example using The same principle follows we have the network portion in blue and we have the host portion in orange.  

Now the next example is a little different, the network portion falls in the middle of the 3rd octet. Still we apply the same principle, we convert it to binary which will mean that the when we convert the subnet mask to binary the first 2 octets will be switched to one’s, the 3rd octet as the network portion shows falls in the middle this means that the octet must have the first set of 1’s switched on and the rest 0’s and the 4th octet all 0’s.

Address Types – Ipv4

We have 3 types of IP addresses:

Network address
Host Address
Broadcast Address

Network address: is used to identify a group of hosts, but how can we identify what is the Network portion and the host portion. This is determined by looking at the subnet mask if we have the subnet mask we can see the last octet is 0’S this means all 8 bits are set to 0. This also means when we look at the last octet in the Network IP its really set to the same as the last octet like in the subnet mask

Example        Network address all zeros in the last octet   Subnet mask all zeros again

The broadcast address   the last octet is with 255 indicating it’s a broadcast address; all devices on the network with the IP address 203.0.113.x will receive broadcast packets. The broadcast in the host portion all the bits are set to 1’s


Host addresses are the individual addresses which we set on the end devices such as routers PCs printer’s laptops tablets etc. etc, the host address what is used the most in networking, broadcasts are the least used. When the host portion is not all 0’s and not all ones you know it’s the host address. See following screenshot


What kind of address ?

It’s a host address, if we convert it to binary it looks like this

11001011 00000000 01110001 00110111 (host address)

11111111 11111111 11111111 00000000 (subnetmask)

What kind of address

11000000 10101000 00001010 00011001 (host address)
11111111 11111111 11111111 00000000 (subnetmask)

Again it’s a host address

11000000 10101000 00001010 11111111

It’s a broadcast address, we can see this directly because the last octet is 255 all 1’s

What kind of address

00001010 00001010 0000000 0000000
11111111 11111111 0000000 0000000

This is a network address because the last octet in the IP is 0 and when we convert 0 to binary address is all 0’s

What kind of address?

Now it gets a little tricky, it appears at first as if it’s a host address but in fact it’s a network address. If convert to binary

11000000 10101000 00001010 01000000
11111111 11111111 11111111 11100000

We can see the last octet is:


We can see the last 5 bits are all set to 0’S so it’s a network address.

Private and Public Addresses


Private Addressing – the following addresses are used in private networks – they cannot be used routed on a public network.

One other private address is its for a local machine, we can use it to test the NIC on a PC to check if the protocol stack is working

If we open a command prompt and type ping it should reply like this:



Ping wird ausgeführt für mit 32 Bytes Daten:

Answer  von Bytes=32 Time<1ms TTL=128
Answer  von Bytes=32 Time <1ms TTL=128
Answer  von Bytes=32 Time <1ms TTL=128
Answer  von Bytes=32 Time <1ms TTL=128

Ping-Statistik für

Pakete: Gesendet = 4, Empfangen = 4, Verloren = 0

(0% Verlust)

Demostrating IP Address Configuration and verification

If we run the following command ipconfig /all

C:\Users\rwelsh>ipconfig /all


   Hostname  . . . . . . . . . . . . : ZAM210
   Primäres DNS-Suffix . . . . . . . :
   Knotentyp . . . . . . . . . . . . : Hybrid
   IP-Routing aktiviert  . . . . . . : Nein
   WINS-Proxy aktiviert  . . . . . . : Nein
   DNS-Suffixsuchliste . . . . . . . :


Ethernet-Adapter LAN-Verbindung 4:


   Verbindungsspezifisches DNS-Suffix:

   Beschreibung. . . . . . . . . . . : Allied Telesis AT-2701FTX PCI Ethernet Adapter – 1 NIC Model
   Physikalische Adresse . . . . . . : 00-15-77-AD-19-97 – MAC ADDRESS
   DHCP aktiviert. . . . . . . . . . : Ja – Set to Receive IP from DHCP Server
   Autokonfiguration aktiviert . . . : Ja – Set to auto negotiate speed from network
   IPv4-Adresse  . . . . . . . . . . : IP address leased
   Subnetzmaske  . . . . . . . . . . : Subnet mask
   Lease erhalten. . . . . . . . . . : 28 October 2015 07:52:16 – Time the leased IP was given
   Lease läuft ab. . . . . . . . . . : 04 November 2015 07:52:12 – Time the leased IP will be released
   Standardgateway . . . . . . . . . : – Standard gateway is simply the router
   DHCP-Server . . . . . . . . . . . : – DHCP server
   DNS-Server  . . . . . . . . . . . : Primary Domain name service Server –  Secondary DNS server –  Third DNS Server


   Primärer WINS-Server. . . . . . . : – Windows Internet Name Server
   NetBIOS über TCP/IP . . . . . . . : Aktiviert

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