The final issue we want to talk about is broadcast domain.

Domains are an issue you are going to hear about, a term you are going to hear over and again in a number of different contexts.

In this context that we are talking about, a domain, a broadcast domain is the region that a broadcast on a network is heard.

Just because we have a switched network doesn't mean to say that we don't do broadcasts. For example, ARP is a broadcast and DHCP is a broadcast.

If you do a arp -p, that 's a broadcast. As said before, what happens with a broadcast is that every workstation hears the broadcast, and they respond to the request.

However what happens in our scenario above: Imagine if every broadcast that was put onto the Internet or on to the network was heard by every single machine on the Internet- clearly we would end up with a quite congested network.

So, a broadcast domain is the area that broadcasts are received, and broadcasts are restricted by routers.

In other words, if the router receives a broadcast it is dropped. This is what we call the broadcast domain, where the domain is the extent to which broadcasts are heard on the Internet or on the network.

In our scenario at ACME Widget Company, we have a router connecting to an ISP 's router, connecting to a server and clients.

When client A broadcasts on the network that 's an ARP request which is a broadcast and because it 's a broadcast everybody is obliged to listen whether you're a router or a server of a workstation, you are obliged to listen.

Because the router restricts the broadcast the extent to which the broadcast will be heard is restricted to that network.

In other words, the router to the Internet will not up-broadcast or will not relay that broadcast message and that is called a broadcast domain.

Sometimes there can be problems on your network where for example, you might have two networks connected by a router. In network A you have a DHCP server and network B you have no DHCP server, you want to offer DHCP IP addresses from network A to network B.

DHCP is a broadcast, router at that point of A entering into the router restricts it. So no DHCP request will ever be answered on the B network.

There are ways around these problems but that 's essentially a broadcast domain and because Linux can be a fully-fledged router, it can handle all these jobs without a problem.