ch3.pdf

JTO Ph-II DNIT CISCO Router Configuration Basics 3 CISCO ROUTERS CONFIGURATION BASICS 3.1 LEARNING OBJECTIVES The objectives of this chapter is to learn i) How to login to router & login options available...

JTO Ph-II DNIT CISCO Router Configuration Basics 3 CISCO ROUTERS CONFIGURATION BASICS 3.1 LEARNING OBJECTIVES The objectives of this chapter is to learn i) How to login to router & login options available ii) Modes of router configuration iii) How to check the links & router interfaces, protocols running iv) Verifying routing table contents v) Configure IP address & bring up router Interfaces to running state vi) Configure login banner on routers 3.2 INTRODUCTION  A router is a device which is having its own specialized Operating System (OS), like all modern electronic devices have. Routers also have RAM, permanent storage, processor and the most important from the network point of view- interfaces or ports. The purpose of configuration of a router is to make it ready to use in the networks for forwarding the traffic. 3.3 BASIC COMPONENTS OF CISCO ROUTER :  Interfaces  The Processor (CPU)  Internetwork Operating System (IOS)  RXBoot Image  RAM  NVRAM  ROM  Flash memory  Configuration Register 3.3.1 INTERFACES These allow us to use the router ! The interfaces are the various serial ports or ethernet ports which we use to connect the router to our LAN. There are a number of different interfaces but we are going to hit the basic stuff only. JTO Ph-II Version 3.0 Aug 2021 Page 30 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics Here are some of the names Cisco has given some of the interfaces: E0 (first Ethernet interface), E1 (second Ethernet interface). S0 (first Serial interface), S1 (second Serial interface), BRI 0 (first B channel for Basic ISDN) and BRI 1 (second B channel for Basic ISDN). Picture below shows the back view of a Cisco router Figure 14: Basic interfaces of a router 3.3.2 THE PROCESSOR (CPU) All Cisco routers have a main processor that takes care of the main functions of the router. The CPU generates interrupts (IRQ) in order to communicate with the other electronic components in the router. The Cisco routers use RISC processors. Usually the CPU utilisation on a normal router wouldn't exceed 20%. 3.3.3 THE IOS The IOS is the main operating system on which the router runs. The IOS is loaded upon the router's bootup. It usually is around 2 to 5MB in size, but can be a lot larger depending on the router series. The IOS gives the router its various capabilities and can also be updated or downloaded from the router for backup purposes. IOS is also available on a PCMCIA Flash card. This Flash card then plugs into a slot located at the back of the router and the router loads the IOS "image". Usually this image of the operating system is compressed so the router must decompress the image in its memory in order to use it. The IOS is one of the most critical parts of the router, without it the router is pretty much useless. Routers can also load the image off a network tftp server or from another router which might hold multiple IOS images for different routers, in which case it will have a large capacity Flash card to store these images. 3.3.4 THE RXBOOT IMAGE The RXBoot image (also known as Bootloader) is nothing more than a "cut- down" version of the IOS located in the router's ROM (Read Only Memory). If you had no Flash card to load the IOS from, you can configure the router to load the RXBoot image, which would give you the ability to perform minor maintenance operations and bring various interfaces up or down. JTO Ph-II Version 3.0 Aug 2021 Page 31 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics 3.3.5 THE RAM The RAM, or Random Access Memory, is where the router loads the IOS and the configuration file. It works exactly the same way as your computer's memory, where the operating system loads along with all the various programs. The amount of RAM your router needs is subject to the size of the IOS image and configuration file you have. Routing tables are also stored in the system's RAM so if you have large and complex routing tables, you will obviously need more RAM ! 3.3.6 THE NVRAM (NON-VOLATILE RAM) The NVRAM is a special memory place where the router holds its configuration. When you configure a router and then save the configuration, it is stored in the NVRAM. This memory is not big at all when compared with the system's RAM. Normally, when a router starts up, after it loads the IOS image it will look into the NVRAM and load the configuration file in order to configure the router. The NVRAM is not erased when the router is reloaded or even switched off. 3.3.7 ROM (READ ONLY MEMORY) The ROM is used to start and maintain the router. It contains some code, like the Bootstrap and POST, which helps the router do some basic tests and bootup when it's powered on or reloaded. You cannot alter any of the code in this memory as it has been set from the factory and is Read Only. 3.3.8 FLASH MEMORY The Flash memory is a card. It is, is an EEPROM (Electrical Eraseable Programmable Read Only Memory) card. It fits into a special slot normally located at the back of the router and contains nothing more than the IOS image(s). You can write to it or delete its contents from the router's console. Usually it comes in sizes of 4MB for the smaller routers (1600 series) and goes up from there depending on the router model. 3.3.9 CONFIGURATION REGISTER The Configuration Register determines if the router is going to boot the IOS image from its Flash, tftp server or just load the RXBoot image. This register is a 16 Bit register, in other words has 16 zeros or ones. A sample of it in Hex would be the following: 0x2102 and in binary is: 0010 0001 0000 0010. When you first power up a new Cisco Router, you have the option of using the ―setup‖ utility which allows you to create a basic initial configuration. However, Command Line Interface (CLI) mode may also be used for configuration. 3.4 MODES OF ROUTER There are mainly 5 modes in router: JTO Ph-II Version 3.0 Aug 2021 Page 32 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics a. User execution mode As soon as the interface up message appears and press enter, the router> prompt will pop up. This is called user execution mode. This mode is limited to some monitoring commands. b. Privileged mode As we type enable to user mode, we enter into Privileged mode where we can view and change the configuration of router. Different commands like show running- configuration, show IP interface brief etc can run on this mode which are used for troubleshooting purpose. c. Global configuration mode As we type configure terminal to the user mode, we will enter into the global configuration mode. Commands enter in these modes are called global commands and they affect the running-configuration of the router. In this mode, different configuration like making local database on router by providing username and password, can set enable and secret password etc. d. Interface configuration mode In this mode, only configuration of interfaces are done. Assigning an IP address to an interface, bringing up the interface are the common tasks done in this mode. e. ROMMON mode We can enter in this mode when we interrupt boot process of the router. Generally, we enter in this mode while password recovery process or Backing up of IOS on device like TFTP server. It is like BIOS mode of a PC 3.5 THE BASIC CLI MODES : Router> enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#hostname Router1 Router1(config)#interface fastethernet 0/0 Router1(config-if)#ip address 192.168.1.1 255.255.255.0 Router1(config-if)#interface fastethernet 0/1 Router1(config-if)#ip address 192.168.4.1 255.255.255.0 Router1(config-if)# In Router 2 --- System Configuration Dialog --- Would you like to enter the initial configuration dialog? [yes/no]: no Router>enable Router#configure terminal Router(config)#hostname Router2 Router2(config)#interface fastethernet 0/0 Router2(config-if)#ip address 192.168.4.2 255.255.255.0 Router2(config-if)#interface fastethernet 0/1 Router2(config-if)#ip address 192.168.3.1 255.255.255.0 JTO Ph-II Version 3.0 Aug 2021 Page 39 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics Router2(config-if)#interface fastethernet 192.168.2.1 255.255.255.0 Router2(config-if)#interface fastethernet 1/0 Router2(config-if)#ip address 192.168.2.1 255.255.255.0 Router2(config-if)# 3.10.4 TASK 2 : CHECK THE IP ADDRESSES CONFIGURED IN TASK 1 & PUT ROUTER INTERFACES INTO RUNNING STATUS FROM DOWN STATUS In Router1 Router1(config-if)#exit Router1(config)#^Z Router1#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 192.168.1.1 YES manual administratively down down FastEthernet0/1 192.168.4.1 YES manual administratively down down Vlan1 unassigned YES unset administratively down down Router1# Bring up the interfaces of Router1: Router1#configure terminal Router1(config)#interface fastethernet 0/0 Router1(config-if)#no shutdown Router1(config-if)#interface fastethernet 0/1 Router1(config-if)#no shut down In Router2 JTO Ph-II Version 3.0 Aug 2021 Page 40 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics Router2#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 192.168.4.2 YES manual administratively down down FastEthernet0/1 192.168.3.1 YES manual administratively down down FastEthernet1/0 192.168.2.1 YES manual administratively down down FastEthernet1/1 unassigned YES unset administratively down down Vlan1 unassigned YES unset administratively down down Bring up the interfaces of Router2: Router2#configure terminal Router2(config)#interface fastEthernet 0/0 Router2(config-if)#no shutdown Router2(config-if)#interface fastEthernet 0/1 Router2(config-if)#no shutdown Router2(config-if)#interface fastEthernet 1/0 Router2(config-if)#no shutdown 3.10.5 TASK 3 CHECK THE CONTENTS OF ROUTING TABLE & ROUTER INTERFACES In Router1 Router1# Router1#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 192.168.1.1 YES manual up up FastEthernet0/1 192.168.4.1 YES manual up up Vlan1 unassigned YES unset administratively down down Router1#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP JTO Ph-II Version 3.0 Aug 2021 Page 41 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics 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, E - EGP i - IS-IS, 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 C 192.168.1.0/24 is directly connected, FastEthernet0/0 C 192.168.4.0/24 is directly connected, FastEthernet0/1 Router1# In Router2 Router2# Router2#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 192.168.4.2 YES manual up up FastEthernet0/1 192.168.3.1 YES manual up up FastEthernet1/0 192.168.2.1 YES manual up up FastEthernet1/1 unassigned YES unset administratively down down Router2#show ip route Codes: C - connected, S - static, I - IGRP, 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, E - EGP i - IS-IS, 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 JTO Ph-II Version 3.0 Aug 2021 Page 42 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics Gateway of last resort is not set C 192.168.2.0/24 is directly connected, FastEthernet1/0 C 192.168.3.0/24 is directly connected, FastEthernet0/1 C 192.168.4.0/24 is directly connected, FastEthernet0/0 Router2# Observation: In both routers only their connected networks appears in the routing table. 3.10.6 TASK 4 RENAME THE ROUTER – FOR EASY IDENTIFICATION In Router 1 Router1>enable Router1#configure terminal Router1(config)#hostname CHN_CDR_KK_NGR CHN_CDR_KK_NGR(config)# CHN_CDR_KK_NGR(config)# In Router 2 Router2>enable Router2#configure terminal Router2(config)#hostname CHN_CORE_NIB CHN_CORE_NIB(config)# CHN_CORE_NIB(config)# 3.10.7 TASK 5 : CONFIGURE LOGIN BANNERS In Router 1 CHN_CDR_KK_NGR>enable CHN_CDR_KK_NGR#configure terminal CHN_CDR_KK_NGR(config)#banner login y ********* WARNING ******** Unauthorised users will be prosecuted - BSNL y CHN_CDR_KK_NGR(config)# In Router 2: Telnet to Router1 CHN_CORE_NIB> JTO Ph-II Version 3.0 Aug 2021 Page 43 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics CHN_CORE_NIB>telnet 192.168.4.1 (IP address of Router1) Table 6. Login Banner 3.10.8 TASK 6 SAVE THE CONFIGURATIONS: Router1>enable Router1#write Building configuration... [OK] Router2>enable Router1#write Building configuration... [OK] 3.10.9 LIST OF COMMANDS USED AND THEIR MEANING Command Purpose ENABLE Escalates privilege to admin role CONFIGURE TERMINAL Gets into global configuration mode INTERFACE Enters into i/f configuration mode JTO Ph-II Version 3.0 Aug 2021 Page 44 of 136 For Restricted Circulation JTO Ph-II DNIT CISCO Router Configuration Basics IP ADDRESS Assigns IP address and subnet mask NO SHUTDOWN Brings UP an interface HOSTNAME To rename a Cisco device To show login message (welcome/ BANNER LOGIN c c warning) ‗c‘ delimit character To come out from a specific configuration EXIT mode Saves the present running configuration as WRITE permanent configuration in NVRAM Table 7. Configuration Commands & their purpose 3.11 CONCLUSION Basic configuration of the router includes configuration of the IP address, host name, banner, secret password, user accounts, and other options. Cisco routers can be configured in several network environments, such as small office home office (SOHO), branch office (BO), regional office, and central site or Enterprise headquarters, with an easy-to-use web-based management interface. JTO Ph-II Version 3.0 Aug 2021 Page 45 of 136 For Restricted Circulation