AAA is an architecture available to all security devices to authenticate users accessing the device or a nearby network. The authorization feature is used to restrict users' privileges after they have been authenticated. Accounting is used to keep logs of the devices' activities, as well as the activities of the users on the network or on network devices. AAA allows its functions to be carried out on a per-user or per-service basis. In other words, it can be used to authenti..
Understanding the Backbone Concept
As mentioned earlier, IS-IS has a two-layer hierarchy. Level 1 routers contain the topology information about their area only, and default to the closest area border router. Level 2 routers route toward the area without considering the internal structure of the area. Level 2 routers patch multiple areas, and contain complete information about routes in other areas. All routers within level 2 must be contiguous—routing between areas passes through the level 2 r..
Problems with Unicast and Broadcast Methods
Why not use unicast or broadcast methods to send a message from one source to many destinations? Figure 19-1 shows a video server as a source of a video application and the video data that needs to be delivered to a group of receivers—H2, H3, and H4—two hops away across a WAN link. Figure 19-1 Unicast The unicast method requires that the video application send one copy of each packet to every group member’s unicast address. To support full-motion, full-screen vi..
Associating the Frame Relay Map Class
After setting up a Frame Relay map class with the default or user-defined traffic shaping parameters, the configured map class has to be associated with a main interface or a subinterface or assigned directly to a VC. For this purpose, the frame-relay class interface configuration command is used to associate a created Frame Relay map class with a specified main interface or subinterface. A user can choose from three levels of a hierarchy when associating a Frame Relay map ..
Preventing Loops with Spanning Tree Protocol
Bridging loops form because parallel switches (or bridges) are unaware of each other. STP was developed to overcome the possibility of bridging loops so that redundant switches and switch paths could be used for their benefits. Basically, the protocol enables switches to become aware of each other so they can negotiate a loop-free path through the network. Note: Because STP is involved in loop detection, many people refer to the catastrophic loops as “spanning-tree lo..
