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Configuring Catalyst Switch
OperationsModule 3
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Objectives
Upon completing this module, you will be able to:
Explain how bridging and switching operates
Explain the purpose and operations of the Spanning-
Tree Protocol
Verify the default configuration of the device, given afunctioning access layer switch
Build a functional access switch configuration to
support the specified network operational parameters,given a network design
Execute an add, move, or change on an access layerswitch, given a new network requirement
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Basic Layer 2 Switching and
Bridging Functions
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Objectives
Upon completing this lesson, you will beable to:
Describe Layer 2 switching and bridgingoperations and modes
Describe how LAN switches use and populatethe MAC address table
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Address learning
Forward/filter decision
Loop avoidance
Ethernet Switches and Bridges
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Cut-Through
Switch checks destination
address and immediately
begins forwarding frame.
Fragment-Free
Switch checks the first 64 bytes,
then immediatelybegins forwarding frame.
Store and Forward
Complete frame is received
and checked before
forwarding.
Transmitting Frames
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A default switching method for Distribution Layer Switches
Latency: High
Error checking: Yes
Store and Forward
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It is also referred as modified cut-through
A default switching method for Access Layer Switches
Latency: Medium
Error Checking: On 64 bytes of Frame
Fragment Free
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A default switching method for the Core Layer Switches
Latency: Low
Error Checking: No
Latency: It is the total time taken for a frame to pass through the switch.
Latency depends on the switching mode and the hardware capabilities of the
switch.
Cut-Through
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MAC Address Table
Initial MAC address table is empty.
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Learning Addresses
Station A sends a frame to station C.
Switch caches the MAC address of station A to port E0 bylearning the source address of data frames.
The frame from station A to station C is flooded out to all
ports except port E0 (unknown unicasts are flooded).
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Learning Addresses (Cont.)
Station D sends a frame to station C.
Switch caches the MAC address of station D to port E3 bylearning the source address of data frames.
The frame from station D to station C is flooded out to all ports
except port E3 (unknown unicasts are flooded).
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Filtering Frames
Station A sends a frame to station C.
Destination is known; frame is not flooded.
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Filtering Frames (Cont.)
Station A sends a frame to station B.
The switch has the address for station B in the MACaddress table.
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Station D sends a broadcast or multicast frame.
Broadcast and multicast frames are flooded to all portsother than the originating port.
Broadcast and Multicast Frames
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Summary
Ethernet switches and bridges increase the availablebandwidth of a network by creating dedicated networksegments and interconnecting the segments.
Switches and bridges use one of three operating modesto transmit frames: store and forward, cut-through, andfragment-free.
Switches and bridges maintain a MAC address table tostore address-to-port mappings so it can determine thelocations of connected devices.
When a frame arrives with a known destination address,it is forwarded only on the specific port connected tothe destination station.
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