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

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Discovering computer networks: hands on in the Open Networking Lab

12.4 Summary of Session 12

In this session you have looked at how both routers and switches make their forwarding decisions based on their relevant addresses, and how MAC addresses are learned from an IP address via the ARP process.

New terms

In this session you have met the following terms.

ARP (address resolution protocol)

A protocol used to find the MAC address of an unknown device on the local network, if you know its IP address.

ARP broadcast

The broadcast MAC address of FF:FF:FF:FF:FF:FF which will be received by all devices on the local network.

ARP reply

The reply data which the device sends back to the source giving its MAC address.

ARP cache

A data table used to temporarily store the IP address to MAC address pairings.


In this context, a type of traffic which is designed to be seen by all devices on the local network, not just a single device.

destination IP address

The IP address of the destination device (where the traffic is heading to).

destination MAC address

The MAC address of the destination device (where the traffic is heading to).

frame header

A block of information put at the start of a frame containing information such as the source and destination MAC addresses and other fields.

ICMP (Internet Control Message Protocol)

A protocol used to report network problems that prevent the delivery of IP packets. Both ping and traceroute use ICMP.

IP packet

The basic unit of data at the Internet layer of the TCP/IP protocol suite.

MAC address table

Also known as ‘forwarding table’. Table used by a switch to associate MAC addresses of devices with port numbers to enable frames to be forwarded to their destination.

PDU (protocol data unit)

The term used to describe the data at each layer of the network model.

source IP address

The IP address the traffic originated from.

source MAC address

The MAC address the traffic originated from.

TCP/IP Internet layer

The layer of the TCP/IP model containing the IP address information.

TCP/IP Network Access layer

The bottom layer of the TCP/IP network model. This is where the hardware sits, along with MAC addresses.


Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371