Are there any tradeoffs or caveats with Transparent mode?
A. There are a few things that you need to be aware of. In transparent mode, you can only bridge pairs of VLANs together. Starting with release 3.1, you can have up to 8 pairs of interfaces per virtual context. Before that, it’s a single pair per context. You lose dynamic routing in transparent mode, as well as NAT/PAT, and unicast RPF-check. Despite the fact that the FWSM runs in transparent mode, some application inspection engines do require static routes to figure out where the end points of the session are located.
