Memory Management
In the section Understanding Router Pieces and Parts, earlier in this chapter, you learned that several types of memory are used some fast and some slower, depending on what the memory is used for. How does Cisco IOS Software manage this memory If a process wants to allocate memory in a fast (or shared) area of memory for processing a packet, how does it do so When the router boots up, Cisco IOS Software divides memory into pools and regions based on the type of memory used. A large variety of...
The adj acency table Forwarding Information Base FIB
The FIB is a dynamically built database of information used by the router to make prefix-based packet-forwarding decisions. The information stored in the FIB is a collection of necessary details copied from the router's global routing table, as well as host route entries. The FIB also precomputes recursive path lookups. The FIB is organized in a way to optimize fast retrieval and longest-match lookups. The FIB is a multiway trie, or simply an mtrie, that stores reachability information about...
FIB Entries
The FIB includes the following entries, referred to by the FIB as flags The following sections discuss each of these entries, detailing how CEF uses them. FIB entries can be viewed on a router using the show ip cef command, as shown in the examples provided in the following sections. An attached FIB entry is created when the destination is directly attached to the router. In Example 2-3, the attached FIB entry represents a statically configured route with the next hop pointing to an interface...
