Over time, the bridges build complete tables for forwarding packets along the tree without extraneous transmissions. There are several disadvantages to transparent bridging. First, the spanning tree protocol must be fairly conservative about activating new links, or loops can develop. Also, all the forwarding tables must be cleared every time the spanning tree reconfigures, which triggers a broadcast storm as the tables are reconstructed. This limits the usefulness of transparent bridging in environments with fluid topologies.
Redundant links can sit unused, unless careful attention is given to root bridge selection.
Finally, like all bridging schemes, the unnecessary broadcasting can affect overall performance. Its use is not recommended in conjunction with low-speed serial links. On the pro side, transparent bridging gives the engineer a powerful tool to effectively isolate high-traffic areas such as local workgroups. It does this without any host reconfiguration or interaction, and without changes to packet format. As usual, careful analysis is needed by the network engineer, with particular attention given to bridge placement.