Instructor: Mr Malik Zaib Chapter 5: Managing a Cisco Internetwork Instructor: Mr Malik Zaib

Chapter 5 Objectives Cisco Router Components Boot Sequence Configuration register Backing up and restoring the IOS Backing up and restoring the configuration Cisco Discovery Protocol Telnet Resolving hostnames Troubleshooting tools 2

Cisco Router Components Bootstrap Brings up the router during initialization POST(Power-on self-test) Checks basic functionality; hardware & interfaces ROM monitor Manufacturing testing & troubleshooting, as well as running a mini-IOS when the IOS in flash fails to load. Mini-IOS Loads Cisco IOS into flash memory, Called the RXBOOT or bootloader by Cisco, the mini-IOS is small IOS in ROM that can be used to bring up an interface and load a Cisco IOS into flash memory. The mini-IOS can also perform a few other maintenance operations. RAM Holds packet buffers, routing tables, & s/w Stores running-config

Cisco Router Components ROM Starts & maintains the router, Holds the POST and the bootstrap program as well as the mini-IOS. Flash Memory Holds Cisco IOS Not erased when the router is reloaded A It is EEPROM (electronically erasable programmable read-only memory) created by Intel. NVRAM Holds router (& switch) configurations Does not store an IOS. Configuration Register Controls how the router boots up By default the value is set to 0x2102, which tells the router to load the IOS from flash memory as well as to load the configuration from NVRAM.

Boot Sequence 1: Router performs a POST 2: Bootstrap looks for & loads the Cisco IOS 3: IOS software looks for a valid configuration file 4: Startup-config file (from NVRAM) is loaded If startup-config file is not found, the router will start the setup mode

Backing up the Configuration 1: Verify the Current Configuration Router#sh run 2: Verify the Stored Configuration Router#sh start Verify available memory 3: Copy running-config to NVRAM Router#copy run start 4: Copy running-config to a TFTP host Router#copy run tftp A second backup

Restoring the Configuration Used when… You need to copy the startup-config to the running-config Errors made in editing the running-config Changes made at the TFTP host need to be copied to the running-config or startup-config Router#copy tftp run or Router#copy tftp start NOTE: The configuration file is ASCII. Any text editor will enable changes Erasing the Configuration Router#erase startup-config Note: When the router reboots it will be in setup mode

Configuring DHCP To configure a DHCP server for your hosts, you need the following information at minimum: Network and mask for each LAN Network ID, also called a scope. All addresses in a subnet can be leased to hosts by default. Reserved/excluded addresses Reserved addresses for printers, servers, routers, etc. These addresses will not be handed out to hosts. I usually reserve the first address of each subnet for the router, but you don’t have to do this. Default router This is the router’s address for each LAN. DNS address A list of DNS server addresses provided to hosts so they can resolve names.

DHCP Configuration Steps Here are your configuration steps: 1. Exclude the addresses you want to reserve. The reason you do this step first is because as soon as you set a network ID, the DHCP service will start responding to client requests. 2. Create your pool for each LAN using a unique name. 3. Choose the network ID and subnet mask for the DHCP pool that the server will use to provide addresses to hosts. 4. Add the address used for the default gateway of the subnet. 5. Provide the DNS server address(es). 6. If you don’t want to use the default lease time of 24 hours, you need to set the lease time in days, hours, and minutes.

DHCP Configuration Commands Switch(config)#ip dhcp excluded-address 192.168.10.1 192.168.10.10 Switch(config)#ip dhcp pool Sales_Wireless Switch(dhcp-config)#network 192.168.10.0 255.255.255.0 Switch(dhcp-config)#default-router 192.168.10.1 Switch(dhcp-config)#dns-server 4.4.4.4 Switch(dhcp-config)#lease 3 12 15 DHCP Configuration example on a switch

DHCP Relay we can configure the F0/0 interface of the router to accept the DHCP client requests and forward them to the DHCP server like this: Router#config t Router(config)#interface fa0/0 Router(config-if)#ip helper-address 10.10.10.254

Verifying DHCP on Cisco IOS There are some really useful verification commands to use on a Cisco IOS device for monitoring and verifying a DHCP service. show ip dhcp binding Lists state information about each IP address currently leased to a client. show ip dhcp pool [poolname] Lists the configured range of IP addresses, plus statistics for the number of currently leased addresses and the high watermark for leases from each pool. show ip dhcp server statistics Lists DHCP server statistics—a lot of them! show ip dhcp conflict If someone statically configures an IP address on a LAN and the DHCP server hands out that same address, you’ll end up with a duplicate address. This isn’t good, which is why this command is so helpful!

Using Cisco Discovery Protocol (CDP) A Cisco proprietary protocol Designed to collect information about directly attached & remote devices Hardware information Protocol information Useful in troubleshooting & documenting the network

Getting CDP Timers & Holdtime Information Configuration CDP Timer: How often CDP packets are transmitted to all active interfaces CDP Holdtime: The amount of time that the device will hold packets received from neighbor devices Router#sh cdp Global CDP information Sending CDP packets every 60 seconds Sending a holdtime value of 180 seconds Router#config t Router(config)#cdp timer 90 Router(config)#cdp holdtime 240

Getting Neighbor Information Shows information about directly connected devices CDP packets are not passed through a Cisco switch Can only see what is directly attached Router#sh cdp nei or Router#sh cdp neighbor detail Detailed information; hostname, IP address, etc

Getting Interface Traffic & Port Information Interface Traffic Information: CDP packets sent & received Errors with CDP Router#sh cdp traffic Port & Interface Information: Encapsulation on the line Timer & Holdtime for each interface Router#sh cdp interface

Documenting the network with CDP

Documented !!

Using Telnet A virtual terminal protocol Part of the TCP/IP suite Allows connections to remote devices Gather information Run programs Note: The VTY passwords must be set on the routers

Using Telnet Setting VTY passwords: Router#config t Router(config)#line vty 0 4 Router(config)#login Router(config)#password cisco Router(config)#^Z Router#172.16.10.2 Trying 172.16.10.2 … Open User Access Verification Password: RouterB>

Using Telnet Setting VTY password: Remember…. Router#config t Router(config)#line vty 0 4 Router(config)#login Router(config)#password cisco Router(config)#^Z Router#172.16.10.2 Trying 172.16.10.2 … Open User Access Verification Password: RouterB> Remember…. VTY password is the user mode (>) password - not the enable mode (#) password With no enable/enable secret password set, the following happens: RouterB>en % No password set RouterB> This equates to good security!

Telnet Commands Telnetting into Multiple Devices Ctrl+Shift+6 (release) X Checking Telnet Connections Router#sh sessions Checking Telnet Users Router#sh users Closing Telnet Sessions RouterB>exit RouterB>disconnect

Resolving Hostnames To use a hostname rather than an IP address to connect to a remote host a device must be able to translate the hostname to an IP address Build a host table on each router Build a Domain Name System (DNS) server

Building a Host Table Provides name resolution only on the router on which it is built [ip host name tcp_port_number ip_address] Router(config)#ip host RouterB 172.16.10.2 Router(config)#ip host switch 192.168.0.148 Router#sh hosts Default TCP port number: 23 Router#RouterB RouterB#(Ctrl+Shift+6) (X) Router#switch

Using DNS to Resolve Names Used when you have many devices on your network Making DNS work… ip domain-lookup Turned on by default ip name-server Sets the IP address of the DNS server (up to 6 each) ip domain-name Appends the domain name to the hostname Ex: RouterA.neversail.navy.mil

Checking Network Connectivity Ping Displays the minimum, average, & maximum times it takes for aping packet to find a specified system + return Router#ping RouterB Trace Shows the path a packet takes to get to a remote device Router#trace RouterB

Summary Go through all the written and review questions Go through the answers with the class 27