Cisco CCNA Certification: Defining Broadcast Domains

When you're studying to pass the CCNA examination and acquire your certification, you're introduced to a cloud of terms that are either altogether new to you alternatively seem familiar, merely you're no quite sure what they are. The term "announce domain" falls into the latter species because many CCNA candidates.

A broadcast domain is simply the group of end hosts that will receive a broadcast sent out by a given host. For sample, if there are ten host devices interlocked to a switch and one of them sends a broadcast, the other nine devices will receive the broadcast. All of those devices are in the same broadcast domain.

Of way, we probably don't want every device in a network receiving every single broadcast sent out by anybody other device in the network! This is why we absence to know what devices can establish multiple, smaller broadcast domains. Doing so allows us to limit the broadcasts traveling approximately our network - and you might be startled how much traffic on some networks consists of unnecessary broadcasts.

Using the OSI prototype, we detect devices such as hubs and repeaters by Layer One. This is the Physical membrane, and devices at this layer have no effect on broadcast domains.

At Layer Two, we've got switches and bridges. By default, a switch has no achieve on broadcast domains; CCNA candidates kas long asa switch ambition amenable a broadcast out each unattached wharf on that switch besides the an upon which it was received. However, Cisco switches permit the production of Virtual Local Area Networks, or VLANs, that are plausible sections of the network. A broadcast sent by one host in a VLAN will not be forwarded out each additional port on the switch. That broadcast will be forwarded merely out ports that are members of the same VLAN for the host appliance that sent it.

The good news is that broadcast traffic will not be forwarded among VLANs. The bad newspaper is that no inter-VLAN traffic at all is allowed by default! You may actually want this in some cases, but generally you're going to want inter-VLAN traffic. This requires the use of a router or other Layer 3 device such as a Layer 3 Switch. (Layer 3 Switches are agreeable more popular every day. Basically, it's a switch that can also run routing protocols. These switches are not tested on the CCNA exam.)

That router we fair talked approximately also defines broadcast domains. Routers do not forward broadcasts, so broadcast domains are defined by routers with no added configuration.

Knowing how broadcasts peregrination across your web, and how they tin be controlled, namely one major part of being a CCNA and of creature a superior network custodian. Best of fortune to you in either of these pursuits!