1. Computer Networks: Bridges 1 Bridges

2. Computer Networks: Bridges 2 Repeater S1S2 S3 LAN1LAN2 S4 A repeater operates at the physical layer and forwards everything between the two LANs. LAN1 and LAN2 are in the same collision domain.

3. Computer Networks: Bridges 3 Figure 6.79 Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks

4. Computer Networks: Bridges 4 Bridges Operate at the data link layer. Bridges use backward learning in recording source addresses 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.

5. Computer Networks: Bridges 5 Bridge Network Physical Network LLC Physical LLC MAC Figure 6.80 A bridge is a store and forward device that separates collision domains. Copyright ©2000 The McGraw Hill CompaniesLeon-Garcia & Widjaja: Communication Networks Bridge

6. Computer Networks: Bridges 6 B1 S1S2 B2 S3S4 S5 Address Port port 1port 2port 1port 2 LAN1LAN2LAN3 Figure 6.81 Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks Bridges

7. Computer Networks: Bridges 7 B1 S1S2 B2 S3S4 S5 Address Port port 1port 2port 1port 2 LAN1LAN2LAN3 S1 S5 S11 1 Figure 6.82 Copyright ©2000 The McGraw Hill CompaniesLeon-Garcia & Widjaja: Communication Networks Bridges

8. Computer Networks: Bridges 8 B1 S1S2 B2 S3S4 S5 Address Port port 1port 2port 1port 2 LAN1LAN2LAN3 S3 S2 S11 1 S32 1 Figure 6.83Copyright ©2000 The McGraw Hill CompaniesLeon-Garcia & Widjaja: Communication Networks Bridges

9. Computer Networks: Bridges 9 S1S2 B2 S3S4 S5 Address Port port 1port 2port 1port 2 LAN1LAN2LAN3 S4 S3 S11 1 S32 1 S42 2 Figure 6.84Copyright ©2000 The McGraw Hill CompaniesLeon-Garcia & Widjaja: Communication Networks Bridge 1 does not forward the frame to LAN1 B1 Bridges MANs with Bridge Loops

10. Computer Networks: Bridges 10 S1S2 S3S4 S5 Address Port port 1port 2port 1port 2 LAN1LAN2LAN3 S2 S1 S11 1 S32 1 S42 2 S21 Figure 6.85Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks Bridge 1 does not forward the frame to LAN2 B1 B2 Bridges

11. Computer Networks: Bridges 11 (1) (2) (3) Figure 6.86Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks MANs with Bridge Loops

12. Computer Networks: Bridges 12 Figure 6.87 Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks One solution to bridge loops Build a Spanning Tree! MANs with Bridge Loops