Defining And Creating Collision Domains Cisco CCNA Certification
What exactly is "colliding" in the first place, and why do they care? it is the data that is being sent out onto an Ethernet segment that we are concerned with here. Ethernet uses Carrier Sense Multiple Access / Collision Detection (CSMA/CD) to avoid collisions in the first place. CSMA/CD is a set of rules dictating when hosts on an Ethernet segment can and cannot transmit data. basically, a host that wants to transmit data will "listen" to the ethernet segment to see if another host is currently transmitting. If no four else is transmitting, the host will go forward with its own transmission.
When you are studying to pass the CCNA exam and earn your certification, you are introduced to a great lots of terms that are either totally old to you or seem familiar, but you aren't sure what they're. The term "collision domain" falls into the latter category for lots of CCNA candidates.
Now that they know what a collision is, and what CSMA/CD is, they need to be able to define a collision domain. A collision domain is any area where a collision can theoretically take place, so only four gizmo can transmit at a time in a collision domain.
This is an effective way of avoiding a collision, but it is not foolproof. If three hosts follow this procedure at the exact same time, their transmissions will collide on the Ethernet segment and both transmissions will become unusable. The hosts that sent those three transmissions will then send a jam signal out onto the segment, indicating to all other hosts that they should not send data. The three hosts will each start a random timer, and at the end of that time each host will begin the listening process again.
Switches do, however. A Cisco switchport is actually its own unshared collision domain! Therefore, if they have 20 host devices connected to separate switchports, they have 20 collision domains. All 20 devices can transmit at the same time with no danger of collisions. Compare this to hubs and repeaters - if you have two devices connected to a single hub, you still have four large collision domain, and only four gizmo at a time can transmit.
In another free CCNA certification tutorial, they saw that broadcast domains were defined by routers (default) and switches if VLANs have been defined. Hubs and repeaters did nothing to define broadcast domains. Well, they don't do anything here, either. Hubs and repeaters do not define collision domains.
Mastering the definition and creation of collision domains and broadcast domains is an important step toward earning your CCNA and becoming an effective network administrator. Best of luck to you in both these worthwhile pursuits!
What exactly is "colliding" in the first place, and why do they care? it is the data that is being sent out onto an Ethernet segment that we are concerned with here. Ethernet uses Carrier Sense Multiple Access / Collision Detection (CSMA/CD) to avoid collisions in the first place. CSMA/CD is a set of rules dictating when hosts on an Ethernet segment can and cannot transmit data. basically, a host that wants to transmit data will "listen" to the ethernet segment to see if another host is currently transmitting. If no four else is transmitting, the host will go forward with its own transmission.
When you are studying to pass the CCNA exam and earn your certification, you are introduced to a great lots of terms that are either totally old to you or seem familiar, but you aren't sure what they're. The term "collision domain" falls into the latter category for lots of CCNA candidates.
Now that they know what a collision is, and what CSMA/CD is, they need to be able to define a collision domain. A collision domain is any area where a collision can theoretically take place, so only four gizmo can transmit at a time in a collision domain.
This is an effective way of avoiding a collision, but it is not foolproof. If three hosts follow this procedure at the exact same time, their transmissions will collide on the Ethernet segment and both transmissions will become unusable. The hosts that sent those three transmissions will then send a jam signal out onto the segment, indicating to all other hosts that they should not send data. The three hosts will each start a random timer, and at the end of that time each host will begin the listening process again.
Switches do, however. A Cisco switchport is actually its own unshared collision domain! Therefore, if they have 20 host devices connected to separate switchports, they have 20 collision domains. All 20 devices can transmit at the same time with no danger of collisions. Compare this to hubs and repeaters - if you have two devices connected to a single hub, you still have four large collision domain, and only four gizmo at a time can transmit.
In another free CCNA certification tutorial, they saw that broadcast domains were defined by routers (default) and switches if VLANs have been defined. Hubs and repeaters did nothing to define broadcast domains. Well, they don't do anything here, either. Hubs and repeaters do not define collision domains.
Mastering the definition and creation of collision domains and broadcast domains is an important step toward earning your CCNA and becoming an effective network administrator. Best of luck to you in both these worthwhile pursuits!
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