1.13 Switching Concepts Flashcards
Summarize switching concepts, including MAC learning and aging, frame switching, frame flooding, and MAC address tables. (26 cards)
In Cisco protocols, which term is often used as a synonym for ‘switch’?
Bridge
While “bridge” was historically used before switches were developed, the term “switch” is more accurate and modern. “Bridge” is less commonly used in current Cisco protocols.
What is a switch’s MAC address table also known as?
- Switching table
- Bridging table
- Content-addressable memory (CAM) table
How do switches learn MAC addresses?
By checking and adding the source MAC address from incoming frames.
The switch records new MAC addresses when receiving frames, associating them with the port they arrived on.
True or False:
When a frame with a new source MAC address arrives, the switch adds it to the MAC address table for the incoming port.
True
This learning process allows the switch to update its MAC address table, optimizing frame forwarding.
Fill in the blank:
The default aging time for MAC address table entries is ______ seconds.
300
Entries are removed if not used within this time frame.
Which command configures the MAC address table aging time?
mac address-table aging-time time-in-seconds
The aging time can be adjusted globally or per VLAN to control how long MAC addresses are stored.
How can you view the aging time of a MAC address entry on a Cisco switch?
Use the show mac address-table aging-time command.
This command displays the current aging time setting for the MAC address table. If no value is specified, it defaults to 300 seconds.
What happens when a switch’s MAC address table is full?
The oldest entry is removed to make space for a new one.
Some switches may broadcast traffic if the table is full.
What does the command ‘show mac address-table dynamic’ display?
It lists all dynamically learned MAC addresses in the MAC table.
This command helps administrators view and troubleshoot the MAC address table.
True or False:
A LAN switch’s primary job is to forward frames to the correct MAC address.
True
A LAN switch operates at Layer 2 and directs Ethernet frames to the appropriate port using the MAC address table for efficient data transmission.
Fill in the blank:
A switch operates at _____ ___ of the OSI model.
Layer 2
(Data Link Layer)
Switches operate at Layer 2, forwarding Ethernet frames based on MAC addresses, making them efficient for LAN communication.
What three actions do switches take to fulfill their primary function?
- Forwarding frames based on the destination MAC address.
- Learning source MAC addresses from incoming frames.
- Preventing loops using Spanning Tree Protocol (STP).
These functions allow switches to efficiently manage network traffic, ensuring proper delivery while avoiding endless frame transmission in redundant networks.
Which command shows the status of STP on a Cisco switch?
show spanning-tree
This command allows network administrators to view STP (Spanning Tree Protocol) status and ensure that no loops exist in the network.
What are the two types of MAC addresses used in switching logic?
- Source MAC address
- Destination MAC address
The source MAC address helps a switch learn device locations, while the destination MAC address allows the switch to determine where to forward frames.
What is a known unicast frame?
A frame with a destination MAC address that is known to the switch.
Unicast frames are forwarded to a specific port rather than being flooded, improving network efficiency.
What does a switch do when it receives an unknown unicast frame?
It floods the frame out all interfaces except the incoming interface.
When a destination MAC address is not in the MAC table, the switch floods the frame to all ports to locate the correct device.
What is the purpose of flooding frames?
To deliver frames when the destination MAC address is unknown.
Flooding helps the switch learn the destination MAC address and update its MAC address table.
What does the command ‘show mac address-table count’ display?
It shows the number of MAC address entries and available table space.
This helps track resource usage on a switch.
What command would you use to check the status of switch interfaces?
‘show interfaces status’
This command displays information about interface status, speed, duplex mode, and VLAN assignments.
What does the command ‘show interfaces f0/1 counters’ provide?
It lists statistics about incoming and outgoing frames on interface F0/1.
This command helps diagnose network traffic by displaying frame counts, errors, and traffic rates.
What command displays MAC addresses from a specific interface?
show mac address-table dynamic interface
This command allows engineers to view MAC addresses associated with a particular port.
Which command removes dynamic MAC address table entries?
clear mac address-table dynamic
This command removes all learned MAC addresses, forcing the switch to relearn them.
What does show mac address-table dynamic vlan [vlan-number] display?
MAC addresses for a specific VLAN.
This command helps in VLAN-based MAC address troubleshooting.
In a scenario with multiple switches, how does MAC learning and forwarding occur?
It happens independently on each switch.
Each switch maintains its own MAC address table, forwarding frames based on local learning.
