What memory of Cisco router is used to store applications processes and data needed to be executed by the CPU?
Initial Configuration of a Router (1.1)A router is essentially a special-purpose computer with an internetwork operating system optimized for the purpose of routing and securing networks. This section will examine the functions of a router and how a router determines the best path. It will also review the command-line interface (CLI) commands required to configure the base settings of a router. Show
Characteristics of a Network (1.1.1.1)Networks have had a significant impact on our lives. They have changed the way we live, work, and play. Networks allow us to communicate, collaborate, and interact in ways we never did before. We use the network in a variety of ways, including web applications, IP telephony, video conferencing, interactive gaming, electronic commerce, education, and more. There are many terms, key structures, and performance-related characteristics that are referred to when discussing networks. These include:
These characteristics and attributes provide a means to compare different networking solutions. Why Routing? (1.1.1.2)How does clicking a link in a web browser return the desired information in mere seconds? Although there are many devices and technologies collaboratively working together to enable this, the primary device is the router. Stated simply, a router connects one network to another network. Communication between networks would not be possible without a router determining the best path to the destination and forwarding traffic to the next router along that path. The router is responsible for the routing of traffic between networks. When a packet arrives on a router interface, the router uses its routing table to determine how to reach the destination network. The destination of the IP packet might be a web server in another country or an email server on the local-area network. It is the responsibility of routers to deliver those packets efficiently. The effectiveness of internetwork communications depends, to a large degree, on the ability of routers to forward packets in the most efficient way possible. Routers Are Computers (1.1.1.3)Most network capable devices (i.e., computers, tablets, and smartphones) require the following components to operate:
A router is essentially a specialized computer. It requires a CPU and memory to temporarily and permanently store data to execute operating system instructions, such as system initialization, routing functions, and switching functions. Routers store data using:
Table 1-1 provides a summary of the types of router memory, their volatility, and examples of what is stored in each. Table 1-1 Router Memory
Unlike a computer, a router does not have video adapters or sound card adapters. Instead, routers have specialized ports and network interface cards to interconnect devices to other networks. Figure 1-1 displays the back panel of a Cisco 1941 ISRG2 and identifies those special ports and interfaces. Routers Interconnect Networks (1.1.1.4)Most users are unaware of the presence of numerous routers on their own network or on the Internet. Users expect to be able to access web pages, send emails, and download music, regardless of whether the server accessed is on their own network or on another network. Networking professionals know that it is the router that is responsible for forwarding packets from network to network, from the original source to the final destination. A router connects multiple networks, which means that it has multiple interfaces that each belong to a different IP network. When a router receives an IP packet on one interface, it determines which interface to use to forward the packet to the destination. The interface that the router uses to forward the packet may be the final destination, or it may be a network connected to another router that is used to reach the destination network. Each network that a router connects to typically requires a separate interface. These interfaces are used to connect a combination of both local-area networks (LANs) and wide-area networks (WANs). LANs are commonly Ethernet networks that contain devices, such as PCs, printers, and servers. WANs are used to connect networks over a large geographical area. For example, a WAN connection is commonly used to connect a LAN to the Internet service provider (ISP) network. Notice that each site in Figure 1-2 requires the use of a router to interconnect to other sites. Even the Home Office requires a router. In this topology, the router located at the Home Office is a specialized device that performs multiple services for the home network. Routers Choose Best Paths (1.1.1.5)The primary functions of a router are to:
The router uses its routing table to determine the best path to use to forward a packet. When the router receives a packet, it examines the destination address of the packet and uses the routing table to search for the best path to that network. The routing table also includes the interface to be used to forward packets for each known network. When a match is found, the router encapsulates the packet into the data link frame of the outgoing or exit interface, and the packet is forwarded toward its destination. It is possible for a router to receive a packet that is encapsulated in one type of data link frame, and to forward the packet out of an interface that uses a different type of data link frame. For example, a router may receive a packet on an Ethernet interface, but must forward the packet out of an interface configured with the Point-to-Point Protocol (PPP). The data link encapsulation depends on the type of interface on the router and the type of medium to which it connects. The different data link technologies that a router can connect to include Ethernet, PPP, Frame Relay, DSL, cable, and wireless (802.11, Bluetooth). Packet Forwarding Mechanisms (1.1.1.6)Routers support three packet-forwarding mechanisms:
Figures 1-3 to 1-5 illustrate the differences between the three packet-forwarding mechanisms. Assume a traffic flow consisting of five packets all going to the same destination. As shown in Figure 1-3, with process switching, each packet must be processed by the CPU individually. Contrast this with fast switching, as shown in Figure 1-4. With fast switching, notice how only the first packet of a flow is process-switched and added to the fast-switching cache. The next four packets are quickly processed based on the information in the fast-switching cache. Finally, in Figure 1-5, CEF builds the FIB and adjacency tables, after the network has converged. All five packets are quickly processed in the data plane. A common analogy used to describe the three packet-forwarding mechanisms is as follows:
Which memory is used in Cisco router?There are four main memory areas within a Cisco router that it's important to be familiar with, namely Flash, RAM, ROM, and NVRAM. Flash memory is implemented (on a Cisco 2500) using two Single Inline Memory Module (SIMM) slots that hold erasable programmable read-only memory (EPROM).
What type of memory is used to store the configuration of the router?The configuration file can be stored in a variety of places, including two inside a router. The router has a couple of other types of memory as well: RAM—Sometimes called DRAM for dynamic random-access memory, RAM is used by the router just as it is used by any other computer: for working storage.
What type of memory is used to store the configuration used by the router when it is up and working?NVRAM (Non-volatile Random Access Memory)
NVRAM is used to store the Startup Configuration File. This is the configuration file that IOS reads when the router boots up. It is extremely fast memory and retains its content when the router is restarted.
What types of memories are used in the Cisco switch?In total, 4 different types of memory are found in Cisco devices.. RAM (DRAM). Flash Memory.. ROM (EPROM). NVRAM.. |