Bridges Networks Bridges 1 S 1 S 2

Bridges Networks: Bridges 1

S 1 S 2 S 4 S 3 LAN 1 LAN 2 Repeater A repeater operates at the physical layer and forwards everything between the two LANs. LAN 1 and LAN 2 are in the same collision domain. Networks: Bridges 2

Copyright © 2000 The Mc. Graw Hill Companies Leon-Garcia & Widjaja: Communication Networks: Bridges

Bridges • Operate at the data link layer. • Bridges use backward learning in recording source address on transmissions. • Unlike repeaters, bridges will not forward a frame onto another LAN segment if it knows about the location of the destination node. • Bridge management gets more complicated when loops are possible in the frame route. Networks: Bridges 4

Bridge Network Bridge LLC MAC MAC Physical A bridge is a store and forward device that separates collision domains. Copyright © 2000 The Mc. Graw Hill Companies Leon-Garcia & Widjaja: Communication Networks: Bridges Figure 6. 80 5

S 1 S 2 S 3 LAN 1 LAN 2 port 1 B 1 Address Copyright © 2000 The Mc. Graw Hill Companies port 2 S 5 S 4 LAN 3 port 1 Port Address Leon-Garcia & Widjaja: Communication Networks: Bridges B 2 port 2 Port Figure 6. 81 6

S 1 S 2 S 3 S 5 S 4 S 5 LAN 1 LAN 2 B 1 port 1 Address S 1 Copyright © 2000 The Mc. Graw Hill Companies port 2 LAN 3 B 2 port 1 Port 1 Address S 1 Leon-Garcia & Widjaja: Communication Networks: Bridges port 2 Port 1 Figure 6. 82 7

S 1 S 2 S 3 LAN 1 S 2 LAN 2 B 1 port 2 LAN 3 B 2 port 1 port 2 Address Port S 1 S 3 1 2 S 1 S 3 1 1 Copyright © 2000 The Mc. Graw Hill Companies S 5 S 4 Leon-Garcia & Widjaja: Communication Networks: Bridges Figure 6. 83 8

S 1 S 2 S 3 S 4 LAN 1 LAN 2 B 1 port 1 Address Bridge 1 does not forward the frame to LAN 1 S 3 S 4 Copyright © 2000 The Mc. Graw Hill Companies port 2 S 5 S 4 S 3 LAN 3 B 2 port 1 Port 1 2 2 Address Port S 1 S 3 S 4 1 1 2 Leon-Garcia & Widjaja: Communication Networks: Bridges port 2 Figure 6. 84 9

S 1 S 2 S 3 S 2 S 1 LAN 2 port 1 Bridge 1 does not forward the frame to LAN 2 S 5 S 4 Bridge 1 port 2 LAN 3 port 1 Bridge 2 port 2 Address Port S 1 S 3 S 4 S 2 1 2 2 1 S 3 S 4 1 1 2 Copyright © 2000 The Mc. Graw Hill Companies Leon-Garcia & Widjaja: Communication Networks: Bridges Figure 6. 85 10

MAN with Bridge Loops LAN 1 (1) B 1 B 2 (2) LAN 2 (1) (2) B 3 (3) (2) (1) B 4 (2) LAN 3 (1) B 5 (2) Copyright © 2000 The Mc. Graw Hill Companies LAN 4 Leon-Garcia & Widjaja: Communication Networks: Bridges Figure 6. 86 11