rrupt Context Switching Dec: 3.253.7.5 Figure 15-5. Optimum-switching multiway tree Dec: 3.253.7.5 Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Figure 15-6. Data stored in optimum-switching multiway tree CEF takes the ideas behind the optimum-switching multiway tree a step further by introducing the concept of a trie. The initial concept is the same as for a multiway or binary tree, but the data is not stored within the nodes. Rather, each node becomes a pointer to another table, which contains the data. Chapter 15: Switching Algorithms in Cisco Routers The term trie comes from the word retrieve, and is pronounced like tree. Some prefer the pronunciation try to differentiate the term from the word "tree." In CEF, this trie is called the forwarding table. Each node is the same static size and contains no data. Instead, the node's position in the trie is itself a reference to another table, called the adjacency table. This table stores the pertinent data, such as MAC header substitution and next-hop information for the nodes. Figure 15-7 shows a rep- resentation of the CEF tables. Dec: 3.253.7.5 Forwarding table Adjacency table Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Forwarding information Figure 15-7. CEF forwarding and adjacency tables One of the biggest advantages of CEF is the fact that the tables are built without process switching. Both tables can be built without waiting for a packet to be sent to a desti- nation. Also, as the forwarding table is built separately from the adjacency table, an error in one 