Discovering computer networks: hands on in the Open Networking Lab
Discovering computer networks: hands on in the Open Networking Lab

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Discovering computer networks: hands on in the Open Networking Lab

2.6 Summary of Session 2

In this session you have learned about IP addresses. The main learning points from the session are summarised below.

An IP address consists of four dotted-denary numbers. Part of the address identifies the network, and part identifies the device on the network. The subnet mask identifies the network part of the address and the device part. The network part of the address must be the same for all devices on the network, but the device part must be unique.

Neither the lowest nor the highest IP address on a network can be allocated to a device. The highest address is used for broadcasting to all devices on a network.

Private local area networks use private IP addresses. These cannot be used on the public internet, but can be reused across multiple networks.

Link-local and loopback addresses can help with the diagnosis of problems in network connectivity.

New terms

In this session you have met the following terms.

core router

A high-speed router carrying traffic on the internet backbone.


An end device on a network such as a smartphone, tablet, laptop.

internet service provider (ISP)

A company that provides a domestic customer, or a business customer, with access to the internet.

link-local address

An IP address allocated to a device when automatic IP allocation fails.

loopback address

An IP address, such as, that simply loops back to the host device.

private address

An IP address that can be used only on private networks such as LANs and home networks, not on the internet. Private addresses are only unique on their own networks.

public address

An IP address that can be used on the public network – the internet. Public addresses must therefore be unique.


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