Configuring Catalyst Switch OperationsIntroducing Basic Layer 2 Switching andBridging Functions
Outline• Overview• Functions of Ethernet Switches and Bridges• Frame Transmission Modes• How Switches and Bridges Learn So...
Ethernet Switches and Bridges   • Address learning   • Forwarding based on the learned addresses   • Loop avoidance
Transmitting FramesCut-Through                            Store and Forward • Switch checks destination            • Compl...
MAC Address Table    • The initial MAC address table is empty.
Learning Addresses• Station A sends a frame to station C.• The switch caches the MAC address of station A to port E0  by l...
Learning Addresses (Cont.)• Station D sends a frame to station C.• The switch caches the MAC address of station D to port ...
Filtering Frames    • Station A sends a frame to station C.    • The destination is known; the frame is not flooded.
Filtering Frames (Cont.)   • Station A sends a frame to station B.   • The switch has the address for station B in the MAC...
Broadcast and Multicast Frames    • Station D sends a broadcast or multicast frame.
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Switch function

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Switch function

  1. 1. Configuring Catalyst Switch OperationsIntroducing Basic Layer 2 Switching andBridging Functions
  2. 2. Outline• Overview• Functions of Ethernet Switches and Bridges• Frame Transmission Modes• How Switches and Bridges Learn Source MAC Addresses• How Switches and Bridges Forward and Filter Frames• Summary
  3. 3. Ethernet Switches and Bridges • Address learning • Forwarding based on the learned addresses • Loop avoidance
  4. 4. Transmitting FramesCut-Through Store and Forward • Switch checks destination • Complete frame is received and address and immediately checked before forwarding begins forwarding frameFragment-Free • Switch checks the first 64 bytes, then immediately begins forwarding frame
  5. 5. MAC Address Table • The initial MAC address table is empty.
  6. 6. Learning Addresses• Station A sends a frame to station C.• The switch caches the MAC address of station A to port E0 by learning 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).
  7. 7. Learning Addresses (Cont.)• Station D sends a frame to station C.• The switch caches the MAC address of station D to port E3 by learning 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).
  8. 8. Filtering Frames • Station A sends a frame to station C. • The destination is known; the frame is not flooded.
  9. 9. Filtering Frames (Cont.) • Station A sends a frame to station B. • The switch has the address for station B in the MAC address table.
  10. 10. Broadcast and Multicast Frames • Station D sends a broadcast or multicast frame.

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