Siemens S223, S323 user manual Sample Configuration, Backup Route

User Manual	UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5

8.3.10Sample Configuration

Backup Route

When you design layer 2 network, you must consider backup route for stable STP net- work. This is to prevent network corruption when just one additional path exits.

Switch B

Switch C

Broken

Aggregation	Switch A
Switch

Switch D

Switch E

PC-A

Fig. 8.26 Example of Layer 2 Network Design in RSTP Environment

In ordinary case, data packets go to Root switch A through the blue path. The black ar- rows describe the routine path to the Aggregation Switch. And the dot lines are in blocking state. But if there is a broken between Switch A and Switch B, the data from PC-A should find another route at Switch D. Switch D can send the data to Switch C and Switch E. Be- cause Switch E has shorter hop count than Switch B, the data may go through the Switch E and A as the red line. And we can assume Switch E is also failed at the same time. In this case, since Switch D can has the other route to Switch C, the network can be stable than just one backup route network.

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