L1 WANs and routers

GV:NguyÔn ViÕt TuyÕn Mobile: 0904 195.090 Email: nviettuyen@gmail.com Wan and Routers Objectives • • • • WANs characteristics Describe the role of a router in a WAN Router components Router connections WANs Introduction to WANs • These are the major characteristics of WANs: – They connect devices that are separated by wide geographical areas – They use the services of carriers – They use serial connections of various types to access bandwidth over large geographic areas WANs characteristics • A WAN operates at the physical layer and the data link layer of the OSI reference model • It interconnects LANs that are usually separated by large geographic areas • WANs provide for the exchange of data packets and frames between routers and switches and the LANs they support WAN Devices Tao Tao xung xung nhip nhip dong dong ho ho Tinh tien dau noi WAN Standards: Protocols Khong can dinh tuyen Typical WAN Layer Links- cac kieu ket noi Chuan dong goi du lieu HDLC, PPP Leased Line bien Packet­switched Chuyen mach goi, cong nghe atm, x X.25, Frame Relay, ATM Service Provider PPP, HDLC Circuit­switched Telephone Comany Routers Router Component: CPU • The Central Processing Unit (CPU) executes instructions in the operating system Among these functions are system initialization, routing functions, and network interface control • The CPU is a microprocessor Large routers may have multiple CPUs Router Component: RAM • RAM, also called dynamic RAM (DRAM), has the following functions: – – – – – Stores routing tables luu tru bang dinh tuyen Holds ARP cache luu bang ARP Holds fast-switching cache Performs packet buffering (shared RAM) Provides temporary memory for the configuration file of the router while the router is powered on – Loses content when router is powered down or restarted Router Component: RAM • RAM provides run time space for executable Cisco IOS software and its subsystems • RAM is usually logically divided into main processor memory and shared input/output (I/O) memory • RAM can be upgraded by adding additional Dual In-Line Memory Modules (DIMMs) Router Component: NRAM • NVRAM has the following characteristics and functions: – Provides storage for the startup configuration file LUU - file khoi dong – Retains content when router is powered down or restarted • In some devices it is implemented in the same flash device Router Component: Flash • Holds the operating system image (IOS) Hdh cua rounter • Allows software to be updated without removing and replacing chips on the processor (co the luu nhieu he dh) • Retains content when router is powered down or restarted • Can store multiple versions of IOS software • Is a type of electronically erasable, programmable ROM (EEPROM) • Adding or replacing the flash Single In-Line Memory Modules (SIMMs) or PCMCIA cards can upgrade the amount of flash Router Component: ROM • Maintains instructions for power-on self test (POST) diagnostics • Stores bootstrap program and basic operating system software, load Cisco IOS software from Flash to RAM • Some routers also have a scaled down version of the IOS that can be used as an alternative boot source • Requires replacing pluggable chips on the motherboard for software upgrades • Luu he dieu hanh co ban, chua chuong trinh khoi dong power-on self test Router Component: Interfaces • Three types of interfaces are local-area network (LANs), wide-area network (WANs), and Console/AUX • Connect router to network for frame entry and exit, or connect to terminal for configuration • Can be on the motherboard or on a separate module (fixed or modular card) Router Component: Interfaces cac giao dien cua • LAN interfaces (Ethernet, FDDI, ATM ) and WAN interfaces(serial, ISDN, CSUs ) have controller chips that provide the logic for connecting the system to the media • The Console/AUX ports are serial ports used primarily for the initial configuration of the router Router Component: Power Supply • The power supply provides the necessary power to operate the internal components • Larger routers may use multiple or modular power supplies • In some of the smaller routers the power supply may be external to the router 2600 External Connection Management Ports • Provides a text-based connection for the configuration, monitoring and troubleshooting of the router • The common management interfaces are the console and auxilliary ports These are EIA-232 asynchronous serial ports • Computer must run a terminal emulation program to provide a text-based session with the router Management Ports Connections Management Ports Connections • The console port is preferred because it displays router startup, debugging, and error messages by default • The console port can also be used when the networking services have not been started or have failed Therefore, the console port can be used for disaster and password recovery procedures Connecting console interfaces • Configure terminal emulation software on the PC for with the appropriate com port and settings • Connect the RJ-45 connector of the rollover cable to the router console port • Connect the other end of the rollover cable to the RJ-45 to DB-9 adapter • Attach the female DB-9 adapter to a PC Summary • • • • • • WANs characteristics WANs standards and protocols Router internal components Router functions Router management ports Router LAN and WAN connection