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

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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.

broadcast

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.