Switching Flashcards
What is a repeater?
Generates a new clean copy of the exact signal
What is a Hub?
A hub is the same as a repeater with more ports; basically a multi port repeater
What layer to hubs and repeaters operate at?
Physical layer
Describe what happens when a collision occurs?
voltage on the wire changes, thats how the device knows a collision has occurred. The devices will then send a jam signal so other devices know not to transmit data due to a collision. Both devices then invoke a “backoff timer”, each will then start the process over again by listening to the wire and transmitting when clear. The backoff timers are totally random so it is unlikely the hosts will have the same problem again.
True or False - Switches break up broadcast domains
False - Routers and VLANS break up broadcast domains, switches add collision domains.
A switch has 12 ports with 12 devices plugged in, how many collision domains are there?
12
What is Microsegmentation?
One host - One collision domain
What will a Cisco switch do with an incoming frame?
Forward it - Flood it - Filter it
How does a switch build a MAC address table?
By looking at the source MAC address
How does a Cisco switch decide what to do with the incoming frame?
The switch will check to see if there is an entry in its MAC address table for the source MAC address and then the switch will use its MAC address table to check if there is an entry for the destination MAC address.
What is the command to see the MAC address table
show mac-address-table
True or False - If the switch does not have an entry for the destination MAC address, it will flood every port with the frame.
False - The switch will flood every port EXCEPT the port the frame came in on.
What is an unknown Unicast Frame?
host to host transmission where the switch doesn’t have the destination MAC address in MAC table.
What does a switch do when it filters the frame?
Drops the frame.
True or False - Switches NEVER send a frame back out the same port it came in on.
True
What is flooding?
Flooding is performed when the switch has no entry for the frame’s destination MAC address. When the frame is flooded it is sent out every port except the one it came in on.
What is Forwarding?
When the switch does have an entry for the frames destination MAC address. The frame will be sent out only one port with Forwarding
What is Filtering?
When the switch has an entry for both the source and destination MAC address and the MAC table indicates that both addresses are found off the same port
What ports are a Broadcast frame sent out on?
Every port except the one that received it. Broadcast frames are intended for all hosts, and the MAC broadcast address is
FF-FF-FF-FF-FF-FF
What is the default time a MAC address is stored?
300 Seconds
Once the switch decides whether to Forward, Filter or Flood the frame…what other decision needs to be made?
What processing method will be used to handle this forwarding. The processing options are: Store-and-forward, Cut-through, fragment-free