3Com 9100 User Manual page 88

88 C 6: S T P (STP)
HAPTER PANNING REE ROTOCOL
Figure 13 Network with an illegal topology
This configuration is illegal because it creates loops that cause the
network to overload. However, STP allows you to use this configuration
because STP detects duplicate paths and immediately prevents (or blocks )
one of them from forwarding traffic.
Figure 14 shows an example of enabling STP on the bridges in the
configuration. The STP system has decided that traffic from LAN segment
2 to LAN segment 1 can only flow through Bridges C and A.
Figure 14 Traffic flowing through Bridges C and A