The primary disadvantages of using routed mode are the following:
• Limited routing protocol choices exist when using multiple-context mode and single-routed mode.
• The configuration can become very complex.
• Multicast support is limited.
If you plan to use multiple contexts, you can choose between static routes and BGP stub. Significant limitations to BGP stub exist (see Chapter 9, "Configuring Routing Protocols," for details), and static routes do not have the capability to propagate routing changes when a next-hop device is unavailable.
If single-routed mode is used, all the access lists for every interface, both inbound and outbound, appear in the configuration. The larger the configuration, the easier it is to overlook configuration mistakes. Careful attention needs to be exercised when adding, removing, or modifying ACLs.
Multicast support is limited to eight outgoing interfaces. In transparent mode, the FWSM does not need to participate in multicast.
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