1 Routing Introduction to Routing Static Routing

2 Objectives Review IP Addressing Introduction to Routing Static Routing Dynamic Routing overview Examples – static routing

3 Data Forwarding How to send information to a distant host? What path is it sent on?  How to find the path? When a computer wants to send data, how does the sending computer know if the Destination computer is on the same network? Host A Host B Host C LAN 1 hostF hostDhostE LAN 2 router WA N / / /24

4 Review – IP Addressing What do all devices on a LAN segment have in common? Host Stevens:    Host Cerf: Host Perlman

5 Data Flow Through a Network

6 Routers –Interfaces Routers have  LAN interfaces Ethernet interfaces:  Have MAC Addresses  IP addresses  WAN interfaces Serial interfaces Have IP addresses Serial Ethernet / MAC: 0abbccddeeff Ethernet / MAC: 0cddeeffaabb

7 What is Routing? Routing - Selecting the correct path towards destination  Build Routing table for path selection  Two methods Static Dynamic Router value in arriving packet’s header routing algorithm local forwarding table header valueoutput link

8 Static Routes A network administrator manually enters route into the router's configuration  When network only consists of a few routers  -Network is connected to internet only through one ISP route entry manually updated whenever network topology changes Static routing reduces overhead Better security

9 Dynamic Routes Route knowledge is updated automatically by a routing process whenever new information is received from the network.

10 Routing Table Structure Routing Table is stored in RAM and contains information about:  Directly connected networks when a device is connected to another router interface  Remotely connected networks network that is not directly connected to a particular router Show ip route command is used to view a routing table

11 Static Routes Specifying Outgoing Interface

12 Static Routes Specifying the Next-hop IP Address

13 Routing Table Structure Static routes in the routing table  -Includes: network address and subnet mask  IP address of next hop router or exit interface  Denoted with the code S in the routing table

14 Review: Default Gateway When a LAN is connected to a Router, Default Gateway is the address of router interface connected to that LAN. The IP address and subnet mask is on the same network as the hosts on that network Router LAN Router Default Gateway

15 Static Routes Verifying Static Route Configuration: The command show running-config is used to view the active configuration in RAM to verify that the static route was entered correctly. The show ip route command is used to make sure that the static route is present in the routing table.

16 Static Routes Troubleshooting Static Route Configuration: The show interfaces command The ping command The traceroute command

17 Review: Cisco Router backplane Identify the different interfaces on router  Interface 1  Interface 2  Interface 3  Interface 4 Serial interface console interface Ethernet interface Interface 1 Interface 2 Interface 3 Interface 4

18 Review: Establishing a Hyper-terminal Session All Cisco routers include an EIA/TIA-232 asynchronous serial console port (RJ-45). How do you connect to router to configure? Router configured from PC connected to router console port using a rollover cable Rollover cable has Serial interface adapter on one side and RJ45 adapter on the other PC Serial adapter RJ45 adapter

19 Connections to the Router- cables Connections of a Router for Ethernet  2 types of cables can be used: Straight through and Cross-over  Straight through used to connect dissimilar devices Switch-to-Router, Switch-to-PC,  Cross-over used to connect similar devices: Switch-to-Switch, Router to PC (Host) PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-Router Cross-overStraight-thru

20 Configuring router Interfaces  -By default all interfaces are down Ethernet Serial  Interface configured with IP address and subnet mask  No Shutdown command used to enable the interface Ethernet interface

21 To configure an Ethernet interface  -Enter interface configuration mode (config)  -Enter IP address and subnet mask  -Enter no shutdown command  Example: -R2(config)#interface fastethernet 0/0 -R2(config-if)#ip address R2(config-if)#no shutdown Configuring Interfaces –Ethernet Interface