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Community Member

term

Hi,

I confuse two technical term:

collision domain

broadcast domain

what is the different of them?

rdgs

1 ACCEPTED SOLUTION

Accepted Solutions
Community Member

Re: term

172.16.1.15 is the broadcast address for the subnet 172.16.1.0 /28. So any broadcast transmitted from any address between 172.16.1.1 - 14 will be switched to each NIC on that network.

Putting vlans aside for a second ... think about this in physical terms instead of logical terms. Think of every switchport as a collision domain. Think of each router port as a broadcast domain (and the switch tree below it). Collision domains make up broadcast domains.

With hubs, you have one collision domain extended out all ports. With switches, you can have multiple broadcast domains traversing one switch via different vlans ... but still, every port on a switch is a separate collision domain. With sub-interfaces on a router, you can have multiple broadcast domains residing on one physical interface.

Routers break up broadcast domains.

Switches extend broadcast domains.

Switches break up collision domains.

Hubs extend collision domains.

4 REPLIES
Community Member

Re: term

A collision domain is traffic off one port of a switch. If you place a hub with 4 computers plugged in, they are all on the same collision domain. When one transmits they all have to cooperate and be quiet or else there will be a collision of traffic on the wire they are sharing. This envokes a formula that all have to calculate in order to determine who gets to talk first.

A broadcast domain is one network segment coming off a router. All users on that network segment (current defintion is vlan) can send traffic to eachother without having to pass traffic to the router. The users can broadcast to eachothers NIC's without worry of that broadcast being forwarded to other broadcast domains, or vlans.

Does that help?

Richard

Community Member

Re: term

Forgot to attach this to better see the difference between Collision Domains and Broadcast Domains.

Community Member

Re: term

Hi Richard,

If the ip address is 172.16.1.1 255.255.255.240

the 172.16.1.15 is broadcast domain

what is the collision domain?

rdgs

Community Member

Re: term

172.16.1.15 is the broadcast address for the subnet 172.16.1.0 /28. So any broadcast transmitted from any address between 172.16.1.1 - 14 will be switched to each NIC on that network.

Putting vlans aside for a second ... think about this in physical terms instead of logical terms. Think of every switchport as a collision domain. Think of each router port as a broadcast domain (and the switch tree below it). Collision domains make up broadcast domains.

With hubs, you have one collision domain extended out all ports. With switches, you can have multiple broadcast domains traversing one switch via different vlans ... but still, every port on a switch is a separate collision domain. With sub-interfaces on a router, you can have multiple broadcast domains residing on one physical interface.

Routers break up broadcast domains.

Switches extend broadcast domains.

Switches break up collision domains.

Hubs extend collision domains.

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