Cisco IOS URL Filtering can act as a backup or as a failover mechanism if the third-party URL filtering server is unavailable or unreachable. A third-party URL filtering server such as Websense or N2H2 is present at the headquarters location. Each branch office points to this server at the headquarters for its URL filtering needs. The requests can be cached at the branch itself using Cisco IOS URL Filtering. Additionally, if the URL filtering server is unreachable, the Cisco IOS URL Filtering static list will act as a backup filtering mechanism, as shown in Figure 2 above.

For larger branch and regional offices that need to offload URL filtering and caching to an external module, a network module is available for Cisco 2800 and 3800 Series routers

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