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Showing posts from October 9, 2010

The Cisco Three-Layered Hierarchical Model

Cisco has defined a hierarchical model known as the hierarchical internetworking model. This model simplifies the task of building a reliable, scalable, and less expensive hierarchical internetwork because rather than focusing on packet construction, it focuses on the three functional areas, or layers, of your network: Core layer : This layer is considered the backbone of the network and includes the high-end switches and high-speed cables such as fiber cables. This layer of the network does not route traffic at the LAN. In addition, no packet manipulation is done by devices in this layer. Rather, this layer is concerned with speed and ensures reliable delivery of packets. Distribution layer : This layer includes LAN-based routers and layer 3 switches. This layer ensures that packets are properly routed between subnets and VLANs in your enterprise. This layer is also called the Workgroup layer. Access layer : This layer includes hubs and switches. This layer is also calle

RIP Routing Fundamentals

RIP stands for Routing Information Protocol. RIP is a dynamic, distance vector routing protocol and was developed for smaller IP based networks. As mentioned earlier, RIP calculates the best route based on hop count. There are currently two versions of RIP protocol. RIPv1, and RIPv2 RIPv1: RIP version 1 is among the oldest protocols. Limitations of RIPv1: 1. Hop Count Limit: Destination that is more than 15 hops away is considered unreachable by RIPv1. 2. Classful Routing Only: RIP is a classful routing protocol. RIPv1 doesn't support classless routing. RIP v1 advertises all networks it knows as classful networks, so it is not possible to subnet a network using RIP v1. 3. Metric limitation: The best route in RIP is determined by counting the number of hops required to reach the destination. A lower hop count route is always preferred over a higher hop count route. One disadvantage of using hop count as metric is that if there is a route with one additional h