Before you can modify port settings, you must select one or more switch ports. Even though they have traditionally been called ports, Catalyst switches running the Cisco IOS Software refer to them as interfaces. To select a single switch port, enter the following command in global configuration mode: Switch(config)# interface type module/number The port is identified by its Ethernet type (fastethernet, gigabitethernet, tengigabitethernet, or vlan), the physical ..
Hellos, Neighbors, and Adjacencies
After a router has been configured for EIGRP, and its interfaces come up, it attempts to find neighbors by sending EIGRP Hellos (destination 224.0.0.10). Once a pair of routers have heard each other say Hello, they become adjacent—assuming several key conditions are met. Once neighbors pass the checks in the following list, they are considered to be adjacent. At that point, they can exchange routes and are listed in the output of the show ip eigrp neighbor command. ■ Mus..
FTP clients and servers use the typical TCP/IP client/server model for the FTP control connection, with the client initiating a TCP connection to well-known FTP port 21. FTP transfers commands and command acknowledgements over the this TCP control connection. However, at some point, data needs to be transferred—and FTP uses a separate but correlated TCP connection for the actual data transfer. FTP clients use one of two modes, passive or active, to define the details of ho..
The Diffusing Update Algorithm
The Diffusing Update Algorithm (DUAL) is the brain behind the operation of EIGRP. It is an algorithm that tracks all the routes advertised from a neighbor and then selects a loop-free path to the destination. Before discussing the details of DUAL, you must understand several terms and concepts: • Feasible distance (FD)— Feasible distance is the minimum metric along the path to a destination. Figure 6-1 shows the feasible distance calculation to reach Network 7 for e..
You can use the offset-list configuration command to modify the metrics of routes that EIGRP learns through a particular interface: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z.Router1(config)#access-list 22 permit 192.168.30.0Router1(config)#router eigrp 55Router1(config-router)#offset-list 22 in 10000 Serial0.1Router1(config-router)#exitRouter1(config)#endRouter1# This command can also modify the EIGRP metrics of routes as the..
