1. © N. Ganesan, All rights reserved. Chapter IP Routing

2. © N. Ganesan, All rights reserved. Module 1 Address Resolution in IP Routing

3. IP Routing Defined The routing of data packets from one network segment to another –For example from from one subnet to another subnet A router (gateway) is often involved in the routing process

4. A Routing Example 190.175.25.20 Router 190.175.26.20 190.175.25.0 190.175.26.0 190.175.25.10 190.175.26.40 Source A Destination B 190.175.26.40

5. Step 1: The Routing Computer A will analyze (AND)the data packet against its subnet masks –The data is to be sent to another subnet Broadcast for the hardware address (eg: CC) of the gateway (IP address is already known) –Using ARP On receiving the hardware address, send the data packet to the gateway (router) to be forwarded to its destination subnet

6. Step 2: The Delivery The router will now be able to deliver the data packet to its destination in the other subnet An analysis of the data packet (ANDing) will determine the destination subnet The gateway will broadcast for the hardware address of the receiving host (IP already known) On receiving a response, the packet will be forwarded to the destination host

7. IP and Hardware Addresses 190.175.25.20 Gateway/Router 190.175.26.20 190.175.25.10 190.175.26.40 Source A Destination B AA CC DDBB

8. Major Routing Methods Static routing –Routing tables are hand maintained at the router Dynamic routing –Routing tables are dynamically maintained by the routing protocol –RIP (Routing Information Protocol) –Open Shortest Path First (OSPF) protocol Static and dynamic routings may be integrated

9. Entries in a Routing Table Network ID (Address) Network (subnet) mask Next hop (Gateway address) Interface –Network interface for forwarding the data packet Metric –Cost of each route for the selection of the best hop

10. Network AddressNetmaskGateway AddressInterfaceMetricPurpose 0.0.0.0 157.55.16.1157.55.27.901Default Route 127.0.0.0255.0.0.0127.0.0.1 1Loopback Network 157.55.16.0255.255.240.0157.55.27.90 1Directly Attached Network 157.55.27.90255.255.255.255127.0.0.1 1Local Host 157.55.255.255255.255.255.255157.55.27.90 1Network Broadcast 224.0.0.0 157.55.27.90 1Multicast Address 255.255.255.255 157.55.27.90 1Limited Broadcast Routing Table of a Host IP Address Gateway Subnet Mask Source: Micrsoft white paper on TCP/IP

11. Obtaining the Routing Table A routing table at a host or a server can be printed by issuing the following command –route print –The above command operates with both Windows 9x and Windows NT

12. End of Module

13. © N. Ganesan, All rights reserved. Module 2 Configuring a Router

14. Configuration of a Router with Windows NT Microsoft NT Server OS can be used to configure a server to act as a router as well Microsoft's MultiProtocol Router (MPR) service must be installed for this purpose Both TCP/IP and IPX routing along with DHCP relaying are supported Also, static and dynamic routing configurations are supported

15. Components of MPR Routing Information Protocol (RIP) for TCP/IP DHCP Relay Agent RIP for IPX Note: NetBEUI is not a routable protocol

16. DHCP Relaying Designed to allow a DHCP server to exist on any subnet Each subnet need not have its own DHCP server A relay agent can relay the request for IP from one subnet to another subnet that contains the DHCP server

17. Router Hardware A router can be a standalone unit –CISCO routers A computer can be configured to function as a router –Such computers often have multiple NICs to connect the different subnets together –Such computers with multiple NICs are often called a multi-homed computer

18. An Example of Router Hardware Configuration NIC 1 NIC 2 Subnet 1 Subnet 2 Computer configured as a router with Windows NT.

19. Enabling Static Routing on Windows NT Ensure that RIP service is installed and started –Use the Network Services in the Service tab under Network properties to install RIP if necessary On the TCP/IP properties, select IP Forwarding to enable routing

20. Adding RIP from Network Services

21. Selecting IP Forwarding

22. © N. Ganesan, All rights reserved. End of Module END OF CHAPTER