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Cisco Router

Cisco Router. Cisco Icons and Symbols. Router. Routers are used to connect networks together Route packets of data from one network to another Cisco became the de facto standard of routers because of their high-quality router products Routers, by default, break up a broadcast domain.

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Cisco Router

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  1. Cisco Router

  2. Cisco Icons and Symbols

  3. Router • Routers are used to connect networks together • Route packets of data from one network to another • Cisco became the de facto standard of routers because of their high-quality router products • Routers, by default, break up a broadcast domain

  4. LANs

  5. WANs

  6. Internetworking Devices

  7. Broadcast and Collision Domain

  8. Broadcast and Collision Domain

  9. Broadcast and Collision Domain

  10. Broadcast and Collision Domain

  11. Using Cisco IOS Command Line Interface (CLI)

  12. Cisco IOS Cisco technology is built around the Cisco Internetwork Operating System (IOS), which is the software that controls the routing and switching functions of internetworking devices. A solid understanding of the IOS is essential for a network administrator.

  13. The Purpose of Cisco IOS As with a computer, a router or switch cannot function without an operating system. Cisco calls its operating system the Cisco Internetwork Operating System or Cisco IOS.

  14. Introduction to Routers A router is a special type of computer. It has the same basic components as a standard desktop PC. However, routers are designed to perform some very specific functions. Just as computers need operating systems to run software applications, routers need the Internetwork Operating System software (IOS) to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. The many parts of a router are shown below:

  15. Router Memory Components ROM -Read Only Memory – Bootstrap/POST FLASH Memory-IOS Images are kept here - Erasable reprogrammable ROM - Contents are kept on Power down or reload RAM - Random Access memory - Routing Tables - Running Configuration - Contents are lost on reboot NVRAM - Start up configuration - Configuration Register - Contents are kept on reload

  16. ROM • Read-Only Memory • ROM has the following characteristics and functions: • Maintains instructions for power-on self test (POST) diagnostics • Stores bootstrap program and basic operating system software • Mini IOS

  17. RAM • Random Access Memory, also called dynamic RAM (DRAM) • RAM has the following characteristics and functions: • Stores routing tables • Holds ARP 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

  18. NVRAM • Non-Volatile RAM • NVRAM has the following characteristics and functions: • Provides storage for the startup configuration file • Retains content when router is powered down or restarted • Configuration Register – 16 bit register which decides boot sequence

  19. Flash • Flash memory has the following characteristics and functions: • Holds the operating system image (IOS) • Allows software to be updated without removing and replacing chips on the processor • 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)

  20. Interfaces Interfaces have the following characteristics and functions: Connect router to network for frame entry and exit Can be on the motherboard or on a separate module Types of interfaces: • Ethernet • Fast Ethernet • Serial • ISDN BRI • Loopback • Console • Aux

  21. Router Internal Components

  22. Router Power-On/Bootup Sequence • Perform power-on self test (POST). • Load and run bootstrap code. • Find the Cisco IOS software. • Load the Cisco IOS software. • Find the configuration. • Load the configuration. • Run the configured Cisco IOS software.

  23. 11 15 8 7 8 8 3 8 14 6 2 4 4 4 12 1 1 0 8 1 4 1 13 2 1 2 9 2 2 5 10 4 Boot Sequence Bootstrap POST C-File NVRAM ROMMonitor RXBoot FLASH ON Running Y OFF LOAD IOS CR N Setup Mode Checks All interfaces Configuration Register RAM 0 0 0 0 0 ROMMonitor 0 1 0 0 RxBoot 1 0 0 0 1 Flash 2-15 1 1 1 1

  24. Boot Sequence

  25. After the Post… After the POST, the following events occur as the router initializes: Step 1 The generic bootstrap loader in ROM executes. A bootstrap is a simple set of instructions that tests hardware and initializes the IOS for operation.  Step 2 The IOS can be found in several places. The boot field of the configuration register determines the location to be used in loading the IOS. Step 3 The operating system image is loaded. Step 4 The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. The configuration commands start routing processes, supply addresses for interfaces, and define other operating characteristics of the router. Step 5 If no valid configuration file exists in NVRAM, the operating system searches for an available TFTP server. If no TFTP server is found, the setup dialog is initiated.  

  26. Loading the Cisco IOS Software From Flash Memory • The flash memory file is decompressed into RAM.

  27. Loading the Configuration • Load and execute the configuration from NVRAM. • If no configuration is present in NVRAM, enter setup mode.

  28. IOS File System Overview

  29. Overview of Router & Switch Modes

  30. Viewing the Configuration

  31. show running-config and show startup-config Commands • Displays the current and saved configuration

  32. Routing Protocols

  33. To route packets, a router needs to do the following: Know the destination address Identify the sources from which the router can learn Discover possible routes to the intended destination Select the best route Maintain and verify routing information Router Operations

  34. Router Operations (Cont.) • The Router knows only the networks it is directly connected to. It must learn all other destinations.

  35. Static Routes A network administrator enters them into the router manually. Dynamic Routes Learned by Routing protocols and added to the routing table. Dynamic routes are adjusted automatically for topology or traffic changes. Static Routes vs. Dynamic Routes Two different ways of learning routes to remote networks:

  36. Static Route Configuration Router(config)#ip route network [mask] {address | interface}[distance] [permanent] • Defines a path to an IP destination network or subnet or host by specifying the next hop router interface IP address. • Address = IP address of the next hop router • Interface = outbound interface of the local router

  37. Static Route Example RouterX(config)# ip route or Router(config)#ip route s0/0/0 • This is a unidirectional route. You must have a route configured in the opposite direction.

  38. Verifying the Static route Configuration RouterA(config)#ip route Serial0/0 RouterA#show ip route Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is not set is subnetted, 2 subnets S [1/0] via, Serial0/0 C is directly connected, Serial0/0

  39. A special case: Default Routes • This route allows the stub network to reach all known networks beyond router A.

  40. Static Routes: Benefits and Disadvantages Benefits:- No overhead on the router CPU - No bandwidth usage between routers - Security and controlDisadvantages:- Administrative burden. - Not practical in large networks.- By default it is not conveyed to other routers as part of an update process.

  41. Dynamic Routing Configuration Defines an IP routing protocol Router(config)#router protocol [keyword] Router(config-router)#network network-number • Mandatory configuration command for each IP routing process • Identifies the physically connected network to which routing updates are forwarded

  42. RIP Overview 19.2 kbps Hop-count metric selects the path. Routes update every 30 seconds. T1 T1 T1

  43. RIP Configuration • Starts the RIP routing process. Router(config)#router rip Router(config-router)#network network-number • Selects participating attached networks. • Requires a major classful network number.

  44. router rip network network router rip network router rip network network RIP Configuration Example e0 s2 s2 s3 s3 e1 A B C

  45. R2(config) router rip R2(config-router)# network R2(config-router)#network R2(config-router)#network Host Name : R1 Host Name : R3 Host Name : R2 .1 .1 .2 .2 Serial 0/1/0 Serial 0/0/0 Serial 0/0/0 Serial 0/0/0 .1 .1 .1 .2 .2 .2 R3(config) router rip R3(config-router)# network R3(config-router)#network R1(config) router rip version 2 R1(config-router)# network R1(config-router)#network Dynamic Route [RIP]

  46. Configuring Single-Area OSPF RouterX(config)# router ospf process-id • Defines OSPF as the IP routing protocol RouterX(config-router)# network addresswildcard-mask area area-id • Assigns networks to a specific OSPF area

  47. Verifying the OSPF Configuration RouterX# show ip protocols • Verifies that OSPF is configured RouterX# show ip route • Displays all the routes learned by the router RouterX# show ip route Codes: I - IGRP derived, R - RIP derived, O - OSPF derived, C - connected, S - static, E - EGP derived, B - BGP derived, E2 - OSPF external type 2 route, N1 - OSPF NSSA external type 1 route, N2 - OSPF NSSA external type 2 route Gateway of last resort is to network O [110/5] via, 0:01:00, Ethernet2 O IA [110/10] via, 0:02:22, Ethernet2 O [110/5] via, 0:00:59, Ethernet2 O [110/5] via, 0:00:59, Ethernet2 O E2 [170/10] via, 0:02:22, Ethernet2 . . .

  48. Verifying the OSPF Configuration (Cont.) RouterX#show ip ospf • Displays the OSPF router ID, timers, and statistics RouterX# showip ospf Routing Process "ospf 50" with ID <output omitted> Number of areas in this router is 1. 1 normal 0 stub 0 nssa Number of areas transit capable is 0 External flood list length 0 Area BACKBONE(0) Area BACKBONE(0) Area has no authentication SPF algorithm last executed 00:01:25.028 ago SPF algorithm executed 7 times <output omitted>

  49. Verifying the OSPF Configuration (Cont.) RouterX# show ip ospf interface • Displays the area ID and adjacency information RouterX#show ip ospf interface ethernet 0 Ethernet 0 is up, line protocol is up Internet Address, Mask, Area AS 201, Router ID, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State OTHER, Priority 1 Designated Router id, Interface address Backup Designated router id, Interface addr Timer intervals configured, Hello 10, Dead 60, Wait 40, Retransmit 5 Hello due in 0:00:05 Neighbor Count is 8, Adjacent neighbor count is 2   Adjacent with neighbor (Backup Designated Router)   Adjacent with neighbor (Designated Router)

  50. Verifying the OSPF Configuration (Cont.) RouterX# show ip ospf neighbor • Displays the OSPF neighbor information on a per-interface basis RouterX#show ip ospf neighbor ID Pri State Dead Time Address Interface   1 FULL/DR 0:00:31 FastEthernet0/0 1 FULL/DROTHER 0:00:33   FastEthernet0/1 1 FULL/DROTHER 0:00:33  FastEthernet0/1   5 FULL/DR 0:00:33  FastEthernet0/1

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