Routing.

Routing

Host Can Send a Packet To Itself
The IP address is a loopback interface that is automatically assigned to a TCP/IP host. Any IP address within the network /8 refers to the local host. Useful for testing purposes. C:\Users\Admin> ping Pinging with 32 bytes of data: Reply from : bytes=32 time<1ms TTL=128 Ping statistics for : Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms C:\Users\Admin>

Host Can Send a Packet To a Local Host
Hosts on the same network, sending host and receiving host share the same network address. PC1 ( /24) sends a packet to PC2 ( /24) Since they are both on the same network ( x /24) the services of a default gateway are not required. .10 PC1 /24 .1 G0/0 .11 PC2 R1 G0/1 .1 .11 PC4 .10 PC3 /24

Host Can Send a Packet To a Remote Host
When a host on a remote network, the hosts do not share the same network address. A default gateway IP address is required. PC1 ( /24) sends a packet to PC4 ( /24) Since they are on different networks ( x /24 and x /24) the services of a default gateway is required. .10 PC1 /24 .1 G0/0 .11 PC2 R1 G0/1 .1 .11 PC4 .10 PC3 /24

Host Can Send a Packet To a Remote Host
The default gateway is the device (i.e, router) that routes traffic from the local network to remote networks. A host sending a packet to a remote host does not maintain routing information beyond the local network. The default gateway maintains a routing table containing directly connected and remote network route information. .10 PC1 /24 .1 G0/0 .11 PC2 R1 G0/1 .1 .11 PC4 .10 PC3 /24

Default Gateway

Configuring Default Gateway on Hosts
The default gateway address can be configured on the host manually or learned dynamically.

Default Gateway – ipconfig
C:\Users\Admin>ipconfig Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : cisco.com Link-local IPv6 Address : fe80::b572:c6c:f983:cadc%11 IPv4 Address : Subnet Mask : Default Gateway : C:\Users\Admin>

C:\Users\Admin> ipconfig /all Windows IP Configuration
Host Name : Admin-wxp Primary Dns Suffix : cisco.com Node Type : Hybrid IP Routing Enabled : No WINS Proxy Enabled : No DNS Suffix Search List : cisco.com Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : cisco.com Description : Intel(R) PRO/1000 PL Network Connection Physical Address : E Dhcp Enabled : Yes Autoconfiguration Enabled : Yes IP Address : Subnet Mask : Default Gateway : DHCP Server : DNS Servers : <Output omitted> C:\Users\Admin>

Host Packet Forwarding Decision
Section So how does a host keep track of whether or not to forward packets to the default gateway? Hosts must maintain their own, local, routing table to ensure that network layer packets are directed to the correct destination network.

Host Routing Table The local table of the host typically contains:
C:\Users\PC1> netstat -r <Output omitted> IPv4 Route Table =========================================================================== Active Routes: The local table of the host typically contains: Direct connection - A route to the loopback interface ( ). Local network route - The host’s network IP address. Local default route - The default route which is the IP address of the network interface of the router that is connected to the local network. The route print or netstat -r command can be used to display the host routing table on a Windows host. Both commands generate the same output. The commands displays interface information, IPv4 route in formation and IPv6 route information Section

netstat IPv4 Information
Lists reachable networks netstat IPv4 Information Lists a subnet mask used by the host to determine the network / host portions of the IP address. Lists the address to get to a remote network. A directly reachable destination displays “On-link”. Lists the address of the physical interface used to send the packet to the gateway. C:\Users\PC1> netstat -r <Output omitted> IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link Lists the cost of each route and is used to determine the best route to a destination. Media Instructions: Media Developer Notes: Media Description: Create a graphic with a sample topology and list the IPv4 section of the Netstat-r command

This is the local default route. Forwards all non-matching packets. All non-matching destination routes are sent to (R1) exiting from the interface with IP address netstat IPv4 Information – These loopback addresses all relate to the direct connection and provide services to the local host. These addresses all relate to the host and local network. The local network route address. The address of the local host. The network broadcast address. C:\Users\PC1> netstat -r <Output omitted> IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link Special multicast addresses reserved for use through either the loopback interface or the host IP address. Media Instructions: Media Developer Notes: Media Description: Create a graphic with a sample topology and list the IPv4 section of the Netstat-r command Limited broadcast IP address values for use through either the loopback interface or the host IP address.

Which route will be chosen?
PC1 wants to ping PC2. Which route will be chosen? C:\Users\PC1> netstat -r <Output omitted> IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link Media Instructions: Media Developer Notes: Media Description: Host routing table with the local network route highlighted.

Which route will be chosen?
PC1 wants to ping Which route will be chosen? C:\Users\PC1> netstat -r <Output omitted> IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link Media Instructions: Media Developer Notes: Media Description: Host routing table with the default network route highlighted.

C:\Users\PC1> netstat -r <Output omitted> IPv6 Route Table =====================================================Active Routes: If Metric Network Destination Gateway ::/ On-link ::1/ On-link ::/ On-link :0:9d38:953c:2c30:3071:e718:a926/128 On-link fe80::/ On-link fe80::/ On-link fe80::2c30:3071:e718:a926/128 fe80::b1ee:c4ae:a117:271f/128 ff00::/ On-link ff00::/ On-link ff00::/ On-link ===================================================== Lists the address of the physical interface used to send the packet to the gateway. Lists the cost of each route and is used to determine the best route to a destination. Media Instructions: Media Developer Notes: Media Description: Create a graphic with a sample topology and list the IPv6 section of the Netstat-r command Lists reachable networks Lists the address to get to a remote network. A directly reachable destination displays “On-link”.

::/0 This is the IPv6 equivalent of the local default route. C:\Users\PC1> netstat -r <Output omitted> IPv6 Route Table =====================================================Active Routes: If Metric Network Destination Gateway ::/ On-link ::1/ On-link ::/ On-link :0:9d38:953c:2c30:3071:e718:a926/128 On-link fe80::/ On-link fe80::/ On-link fe80::2c30:3071:e718:a926/128 fe80::b1ee:c4ae:a117:271f/128 ff00::/ On-link ff00::/ On-link ff00::/ On-link ===================================================== ::1/128 This is equivalent to the IPv4 loopback address and provides services to the local host. 2001:: Global Unicast Addresses 2001::/32 - This is the global unicast network prefix. •2001:0:9d38:953c:2c30:3071:e718:a926/128 - This is the global unicast IPv6 address of the local computer. fe80:: Link Local Addresses fe80::/64 - This is the local link network route address and represents all computers on the local link IPv6 network. fe80::2c30:3071:e718:a926/128 - This is the link local IPv6 address of the local computer. Media Instructions: Media Developer Notes: Media Description: Create a graphic with a sample topology and list the IPv6 section of the Netstat-r command ff00::/8 Multicast Addresses These are special reserved multicast class D addresses equivalent to the IPv4 224.x.x.x addresses.

Default Gateway on a Switch
S1# show running-config Building configuration... ! <output omitted> service password-encryption hostname S1 Interface Vlan1 ip address ip default-gateway /24 .10 PC1 .11 PC2 /24 .1 G0/1 G0/0 R1 S2 S1 .5 Section A switch must (should) also be configured with a default gateway address, because packets that originate from the switch are handled just like packets that originate from a host device. This is not used by normal user frames! Use the ip default-gateway global config command.

Default Gateway on a Switch
For example, the administrator wants to Telnet to the S1. Without the default gateway configured on S1, packets from S1 would not be able to reach the administrator at S1# show running-config Building configuration... ! <output omitted> service password-encryption hostname S1 Interface Vlan1 ip address ip default-gateway Section /24 .10 PC1 .11 PC2 /24 .1 G0/1 G0/0 R1 S2 S1 .5

Router Routing Tables

Routers A router is the main infrastructure device that makes forwarding decisions on any network. It’s goal is to forward a packet to its correct destination! To do so, a router keeps track of local and remote networks. This information is stored in a routing table.

Routing IP Packets

Router Operational Goal
Once a router receives a frame … De-capsulates the data link header. Examines the IP address to determine the destination network. Consults its routing tables to determine which of its interfaces it will use to send the frame. It encapsulates the frame and forwards it.

Routing IP Packets

Routing Table Routes Section

Routing Table Routes The routing table of a router stores information about: Directly-connected routes: These routes come from the active router interfaces. Routers Add a directly connected route when an interface is configured with an IP address and is activated. Remote routes: These routes come from remote networks connected to other routers. Routes to these networks can either be manually configured or dynamically learned using a dynamic routing protocol.

Routers and the Network Layer

IPv4 Router Routing Table
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1#show ip route Codes: L - local, 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, 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 /8 is variably subnetted, 2 subnets, 2 masks D /24 [90/ ] via , 00:00:05, Serial0/0/0 D /24 [90/ ] via , 00:00:05, Serial0/0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/1 L /32 is directly connected, GigabitEthernet0/1 /24 is variably subnetted, 2 subnets, 3 masks C /30 is directly connected, Serial0/0/0 L /32 is directly connected, Serial0/0/0 R1# Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section

Directly Connected Interfaces
/24 .10 G0/0 .1 PC1 /30 .225 S0/0/0 R1 .1 G0/1 .10 PC2 /24 Two routing table entries are automatically created when an active router interface is configured with an IP address and subnet mask. C: Identifies a directly connected network. Directly connected networks are automatically created when an interface is configured with an IP address and activated. L: Identifies that this is a local route, the IP address of the interface. Local routes are automatically created when an interface is configured with an IP address and activated.

Directly Connected Routing Table Entries
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 A B C C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section A Identifies how the network was learned by the router. B Identifies the destination network and how it is connected. C Identifies the interface on the router connected to the destination network.

Remote Network Routing Table Entries
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 D /24 [90/ ] via , 00:00:05, Serial0/0/0 A Identifies how the network was learned by the router. B Identifies the destination network. C Identifies the administrative distance (trustworthiness) of the route source. D Identifies the metric to reach the remote network. E Identifies the next hop IP address to reach the remote network. F Identifies the amount of elapsed time since the network was discovered. G Identifies the outgoing interface on the router to reach the destination network. Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section

Destination Network 192.168.10.0/24 10.1.1.0/24 209.165.200.224 /30 R1
G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1#show ip route Codes: L - local, 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, 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 /8 is variably subnetted, 2 subnets, 2 masks D /24 [90/ ] via , 00:00:05, Serial0/0/0 D /24 [90/ ] via , 00:00:05, Serial0/0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/1 L /32 is directly connected, GigabitEthernet0/1 /24 is variably subnetted, 2 subnets, 3 masks C /30 is directly connected, Serial0/0/0 L /32 is directly connected, Serial0/0/0 R1# Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section

Next-Hop Address 192.168.10.0/24 10.1.1.0/24 209.165.200.224 /30 R1 R2
G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1#show ip route Codes: L - local, 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, 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 /8 is variably subnetted, 2 subnets, 2 masks D /24 [90/ ] via , 00:00:05, Serial0/0/0 D /24 [90/ ] via , 00:00:05, Serial0/0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/1 L /32 is directly connected, GigabitEthernet0/1 /24 is variably subnetted, 2 subnets, 3 masks C /30 is directly connected, Serial0/0/0 L /32 is directly connected, Serial0/0/0 R1# Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section

Which Route? PC1 wants to ping another host on the same network
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1#show ip route Codes: L - local, 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, 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 /8 is variably subnetted, 2 subnets, 2 masks D /24 [90/ ] via , 00:00:05, Serial0/0/0 D /24 [90/ ] via , 00:00:05, Serial0/0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/1 L /32 is directly connected, GigabitEthernet0/1 /24 is variably subnetted, 2 subnets, 3 masks C /30 is directly connected, Serial0/0/0 L /32 is directly connected, Serial0/0/0 R1# Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section

Which Route? PC1 wants to ping PC2 192.168.10.0/24 10.1.1.0/24
/24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1#show ip route Codes: L - local, 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, 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 /8 is variably subnetted, 2 subnets, 2 masks D /24 [90/ ] via , 00:00:05, Serial0/0/0 D /24 [90/ ] via , 00:00:05, Serial0/0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/1 L /32 is directly connected, GigabitEthernet0/1 /24 is variably subnetted, 2 subnets, 3 masks C /30 is directly connected, Serial0/0/0 L /32 is directly connected, Serial0/0/0 R1# Media Instructions: Media Developer Notes: Media Description: Create the graphic as shown, highlighting the appropriate section

Which Route? PC1 wants to ping the R2 WAN Interface 192.168.10.0/24

Which Route? PC1 wants to ping 10.1.1.10 192.168.10.0/24 10.1.1.0/24

Routers

Types of Routers Cisco Routers Branch Routers WAN Routers
Designed for teleworkers, small business, and medium-size branch sites. Includes Cisco 800, 1900, 2900, and 3900 Integrated Series Routers (ISR) G2. WAN Routers 7200 Series Router Large businesses, organizations, and enterprises. Includes the Cisco Aggregation Service Router (ASR) 1000, 7200 Series Router, and the Cisco Catalyst 6500 Series Switches. Service Provider Routers CRS-1 Multishelf System Large service providers. Includes Cisco CRS-3 Carrier Routing System, Cisco ASR 9000, Cisco ASR 1000, Cisco XR 12000, and 7600 Series routers CRS-3 support s bandwidths of up to 322 Tb/s.

How Fast is 322 Tb/s?

Router Components Regardless of their function, size or complexity, all router models are essentially computers and require: Operating systems (OS) Central processing units (CPU) Random-access memory (RAM) Read-only memory (ROM) Routers also have special memory that includes Flash and nonvolatile random-access memory (NVRAM).

(Random Access Memory)
Router Memory Memory Volatile / Non-Volatile Stores RAM (Random Access Memory) Volatile Running IOS Running configuration file IP routing and ARP tables Packet buffer ROM (Read-Only Memory) Bootup instructions Basic diagnostic software Limited IOS NVRAM (Non-Volatile RAM) Startup configuration file Flash IOS Other system files Section

Router Front System Power LED System Activity LED
Solid green indicates the presence of power. System Activity LED Blinks when packets are transmitted or received on any WAN or LAN interface.

Router Backplane 4-port EtherSwitch HWIC 2 port Smart Serial HWIC
High-speed WAN Interface Card 2 port Smart Serial HWIC Compact Flash Module Stores Cisco IOS Integrated ports Console, Auxiliary, and FastEthernet

Double-wide eHWIC slots
Router Backplane Double-wide eHWIC slots eHWIC 0 AUX port LAN interfaces The backplane of a router includes: Section Console RJ45 USB Ports Two 4 GB flash card slots Console USB Type B

Double-wide eHWIC slots
Connecting to a Router AUX port LAN interfaces Double-wide eHWIC slots eHWIC 0 Cisco router ports can be grouped into two categories: Management ports – Includes console and auxiliary ports used to configure, manage, and troubleshoot the router. Inband Router interfaces – Includes LAN and WAN interfaces configured with IP addressing to carry user traffic. Section Console RJ45 Console USB Type B

Console and Ethernet Connections

Console Port

Auxiliary Ports

Router Interfaces A router interface is a physical connector that enables a router to send or receive packets Each interface connects to a separate network Consist of socket or jack found on the outside of a router Types of router interfaces: Ethernet FastEthernet Gigabit Ethernet Serial DSL Cable ISDN

LAN and WAN Interfaces Serial interfaces LAN interfaces
Router interfaces can be grouped into two categories: Ethernet LAN interfaces: Requires an IP address and enabled. Serial WAN interfaces – Requires an IP address and enabled. Serial interfaces Section LAN interfaces

Router Bootup

Cisco IOS The IOS file itself is several megabytes in size and similar to Cisco IOS switches, is stored in flash memory. IOS stored in Flash can be upgraded to newer versions or to have new features added. During bootup, the IOS is copied from slower flash memory into faster RAM (DRAM).

Bootset Files During bootup, the router loads two files into RAM:
IOS: Copied from flash into RAM. Startup configuration: Copied from NVRAM into RAM. Section

Router Bootup Process Note:
Both POST and the Bootstrap program are located in ROM. Load IOS from Flash. None in Flash, then load from TFTP server. Load from NVRAM. None in NVRAM, then load from TFTP server. No Server/file, then enter Setup mode from the console. Section Note: Setup mode is not used in this course to configure the router. When prompted to enter setup mode, always answer no. If you answer yes and enter setup mode, press Ctrl+C at any time to terminate the setup process.

Show Versions Output Section 6.3.2.4
Version of the Cisco IOS software in RAM and that is being used by the router. Router# show version Cisco IOS Software, C1900 Software (C1900-UNIVERSALK9-M), Version 15.2(4)M1, RELEASE SOFTWARE (fc1) Technical Support: Copyright (c) by Cisco Systems, Inc. Compiled Thu 26-Jul-12 19:34 by prod_rel_team ROM: System Bootstrap, Version 15.0(1r)M15, RELEASE SOFTWARE (fc1) Router uptime is 10 hours, 9 minutes System returned to ROM by power-on System image file is "flash0:c1900-universalk9-mz.SPA M1.bin" Last reload type: Normal Reload Last reload reason: power-on <Output omitted> Cisco CISCO1941/K9 (revision 1.0) with K/77824K bytes of memory. Processor board ID FTX Z 2 Gigabit Ethernet interfaces 2 Serial(sync/async) interfaces 1 terminal line DRAM configuration is 64 bits wide with parity disabled. 255K bytes of non-volatile configuration memory. 250880K bytes of ATA System CompactFlash 0 (Read/Write) Technology Package License Information for Module:'c1900' Technology Technology-package Technology-package Current Type Next reboot ipbase ipbasek Permanent ipbasek9 security None None None data None None None Configuration register is 0x2142 (will be 0x2102 at next reload) Router# Displays the system bootstrap software version stored in ROM that was initially used to boot up the router. Displays the complete filename of the IOS image and where the it was loaded from. Identifies the type of router and the amount of DRAM. Some routers, like the Cisco 1941 ISR, use a fraction of DRAM as packet memory for buffering packets. Add both numbers to determine the total amount of DRAM. Displays the physical interfaces on the router. In this example, the Cisco 1941 ISR has two Gigabit Ethernet interfaces and two low-speed serial interfaces. Displays the amount of NVRAM and Flash. Section Displays the licensing information of the router. The IOS can be upgraded to support additional features. Displays the software configuration register in hexadecimal. A second value in parentheses denotes the value that is used during the next reload. For example, 0x2102 indicates that the router attempts to load a Cisco IOS software image from flash memory and load the startup configuration file from NVRAM

Configuring a Cisco Router
Section 6.4

Configure Initial Router Settings
Cisco routers and switches use the same CLI. They support similar command structures, and commands. The following steps should be completed on a router: Assign a device name using the hostname global config command. Secure privileged EXEC mode access using the enable secret command. Secure EXEC mode access using the login command on the console port, and the password command to set the password. Secure virtual access similar to securing EXEC access mode, except on the Virtual Teletype (VTY) port. Use the service password-encryption global configuration command to prevent passwords from displaying as plain text in the configuration file. Provide legal notification using the banner motd (message of the day [MOTD]) global configuration command. Save the configuration using the copy run start command. Verify the configuration using the show run command.

Router Configuration Steps
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 Router> enable Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# hostname R1 R1(config)# R1(config)# enable secret class R1(config)# line console 0 R1(config-line)# password cisco R1(config-line)# login R1(config-line)# exit R1(config)# line vty 0 4 R1(config)# service password-encryption R1(config)# banner motd # Enter TEXT message. End with the character '#'. *********************************************** WARNING: Unauthorized access is prohibited! # R1(config)# exit R1# R1# copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] Section

Router Interfaces Router interfaces must be configured.
Cisco routers support a wide range of interfaces however, in our lab the routers support. FastEthernet 0/0 (Fa0/0) FastEthernet 0/1 (Fa0/1) Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)

Configuring Router Interfaces
To enable a router interface, configure the following: Enter interface config mode: interface type-and-number Add description (optional): description descriptive-text IPv4 address and subnet mask: ip address address subnet-mask Activate the interface: no shutdown

Configure LAN Interfaces
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1# conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)# R1(config)# interface gigabitethernet 0/0 (Note : Our routers use FastEthernet 0/0) R1(config-if)# description Link to LAN-10 R1(config-if)# ip address R1(config-if)# no shutdown %LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up R1(config-if)# exit Section

Configure LAN Interfaces
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1(config)# int g0/1 (Note : Our routers use FastEthernet 0/1) R1(config-if)# description Link to LAN-11 R1(config-if)# ip add R1(config-if)# no shut %LINK-5-CHANGED: Interface GigabitEthernet0/1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up R1(config-if)# exit R1(config)# Section

Configure WAN Interface
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1(config)# interface s0/0/0 R1(config-if)# description Link to R2 R1(config-if)# ip add R1(config-if)# clock rate R1(config-if)# no shutdown LINK-5-CHANGED: Interface Serial0/0/0, changed state to up R1(config-if)# exit R1(config)# Section

Verify Basic Config R1# show ip interface brief
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1# show ip interface brief Interface IP-Address OK? Method Status Protocol GigabitEthernet0/ YES manual up up GigabitEthernet0/ YES manual up up Serial0/0/ YES manual up up Serial0/0/ unassigned YES NVRAM administratively down down R1# ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds: !!!!! R1# Section

Verify the Routing Table
/24 /24 .10 G0/0 .1 .10 PC1 /30 .1 .225 S0/0/0 .226 R1 R2 .1 G0/1 .10 .1 .10 PC2 /24 /24 R1# show ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area <Output omitted> Gateway of last resort is not set /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/0 L /32 is directly connected, GigabitEthernet0/0 /24 is variably subnetted, 2 subnets, 3 masks C /24 is directly connected, GigabitEthernet0/1 L /32 is directly connected, GigabitEthernet0/1 /24 is variably subnetted, 2 subnets, 3 masks C /30 is directly connected, Serial0/0/0 L /32 is directly connected, Serial0/0/0 R1# Section

Remember … As a packet travels from one networking device to another
The Source and Destination IP addresses NEVER change The Source & Destination MAC addresses CHANGE as packet is forwarded from one router to the next. TTL field decrement by one until a value of zero is reached at which point router discards packet (prevents packets from endlessly traversing the network)

A Day in the Life of a Packet

Routing.

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Routing.

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