This tutorial is going to be focusing on two major things collision domains and broadcast domains. You should aware of two different types of domains when designing a LAN otherwise both of these domains can harm the performance of your network. If you are not aware of the difference between these two domains, this tutorial should help you out.
A collision domain is a section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters, in particular when using early versions of Ethernet the set of LAN devices whose frames could collide with one another. In Collision domain with hubs, bridges, repeaters and wireless access points as only one device can send and receive at a time. If more than one device tries sending or receiving, the information is lost and irrecoverable it will need to be resent. This can slow down network performance along with making it a security threat.
A broadcast domain is a logical division of a computer network with nodes, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments.
The definition of a broadcast domain is a set of devices that if one device sends a broadcast frame all other devices will receive that frame in the same broadcast domain. So if devices are in the same IP network they will be able to receive a broadcast message. Having a smaller broadcast domain can improve network performance and improve against security attacks. The more PCs and network devices connected to a single broadcast domain, the more broadcast messages you will have. Remember a broadcast message goes to every PC and network device.
Difference between Collision domain and Broadcast domain
1. Layer 1 of the OSI model
2. A collision domain is a link where collisions can occur between transmitting devices.
3. Collision Domains are defined by Layer 2 devices
4. Only one device in the collision domain may transmit at any one time
5. Collision domain may not be broadcast domain
1. Layer 2 of the OSI model
2. A Broadcast domain is a link where broadcast can occur between devices.
3. Broadcast Domains are defined by Layer 3 devices
4. All devices in the collision domain can transmit at any time
5. Broadcast domain may be collision domain
Find the Collision and Broadcast Domains in Cisco Switch
In Cisco Switch, each port is a separate collision domain, So each connection from a single PC to a Layer 2 switch is ONE Collision domain. For example, if 2 PCs are connected with separate cables to a switch, so we have 2 Collision domains. If this switch is connected to another switch or a router, we have one collision domain more and total 3 collision domains and every Switch having one broadcast domain by default.
Example: Cisco 24 port Catalyst Switch, collision domains = 24 and broadcast domains=1
Cisco 48 port Catalyst Switch, collision domains = 48 and broadcast domains=1
Collision Domain and Broadcast Domains in Hub
In hubs, number of collision domains no way related to how many ports/hosts or devices are connected together, if they are connected with a repeater, hub, switch or bridge, all these devices are in ONE collision domain and it also having only one broadcast domain by default. A Router is used to separate Broadcast-Domains. So, if a router stands between all these devices, we have TWO broadcast domains.
Example: Hub with 4 ports, collision domains = 1 and broadcast domains=1
Hub with 8ports , collision domains = 1 and broadcast domains=1
Filed Under: Ethernet
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