Lab 9 - Static Routing

From SOFTICE

Pedagogical Objectives

• Review the design and implementation of subnetting schemes
• Build upon the Subnetting lab to explain routing
• Implement static routing

Developed by:

• Matt Rideout

Synopsis

Routing is the process by which networking traffic is directed to its final destination through the use of OSI Model Layer 3 information. In this lab, we will examine how this is works, and implement static (manually configured) routing. A future lab will discuss routing protocols, and how they can be used to enable networks to find routes without human intervention.

[Briefing]

In IP networks, routers direct traffic based on each packet's destination IP address field. If the destination IP address is on a subnet that the router is directly connected to, the router sends the packet out onto that network. Otherwise, the destination IP address is compared to the routing table's contents, in order to identify the best match. At this stage, one of three things can happen:

• If a single match is found, the packet is forwarded out of the interface that connects to the next hop router.
• If multiple matches are found, the most specific matching route is selected, and the packet is forwarded out of the interface that connects to the next hop router. A route to the 10.0.0.0/24 network, for example, is considered to be more specific than a default route, and so takes precedent.
• If no match is found, the packet is discarded.

In this lab, we will add static routes using the route command.

[Solved] Subnet and Configure Routing for the Two Locations Network

Complete the following solved exercise, recording your findings, and the procedures used to obtain them in your log. By doing this, you may be able to obtain partial credit if you are unable to complete any of the exercises.

Note: Before disconnecting from SOFTICE, be sure to shut your virtual hosts down. This procedure is described in Exercise 1-3: Shutdown the Network. This must be done in order to conserve system resources on the SOFTICE cluster.

In this solved example, we are going to use the route command to populate the routing tables.

1. The Two Locations Network has already been assigned IP addresses. Use the unedited twoLocations.mln file located in your mln/mln_files directory to build the Two Locations Network, then start it up.

mln build -f mln/mln_files/twoLocations.mln
mln start -p twoLocations

Use the route command to configure routing so that all hosts have networking connectivity to each other.

2. The server host has only one interface, with only one router (tampa) to send routed IP traffic to. Therefore, we can configure routing on server by simply adding a default route to server's routing table. The tampa router's interface that is located on the tampa LAN (Local Area Network) will become the server host's default route:

route add default gw 10.0.1.1

Let's break apart the above command:

• route is the name of the application that's used to work with the routing table

• add tells route to prepare to create a new entry

• The next argument tells route the destination of the new entry. In this instance default is used to tell route that the new entry will be the host's default route

• After route is told the destination of the new entry, it's time to tell it the next gateway (next hope router) for this route. The gateway is the IP address of the host that will forward packets that match this new route. In this case, the next hop is 10.0.1.1, so the gateway is specified with gw 10.0.1.1. This is the tampa host's LAN interface

3. The tampa router has two interfaces. One connects to the server host, and the other connects to the lakeland router. Since the tampa router's two interfaces are directly connected to the tampa LAN (Local Area Network), and Lakeland-to-Tampa WAN (Wide Area Network), there is no need to configure routes for those two networks. This means that the tampa router only needs to have a route added for the lakeland network. The lakeland router's interface that is located on the Lakeland-to-Tampa WAN will become the tampa router's route to this network:

route add -net 10.0.0.0 netmask 255.255.255.0 gw 10.0.3.1

The above route command is different from the command that was executed in step 2 in two ways:

• The destination is different. -net 10.0.0.0 netmask 255.255.255.0 tells route that the destination for this new entry is 10.0.0.0/24

• The gateway (gw) for this destination is 10.0.3.1 - the lakeland router's WAN interface

4. The lakeland router has two interfaces. One connects to the client host, and the other connects to the tampa router. Since the lakeland router's two interfaces are directly connected to the Lakeland LAN, and Lakeland-to-Tampa WAN, there is no need to configure routes for those two networks. This means that the lakeland router only needs to have a route added for the Tampa LAN. The tampa router's interface that is located on the Lakeland-to-Tampa WAN will become the lakeland router's route to this network:

route add -net 10.0.1.0 netmask 255.255.255.0 gw 10.0.3.2

5. The client host has only one interface, with only router (lakeland) to send routed IP traffic to. Therefore, we can configure routing on client by simply adding a default route to server's routing table. The lakeland router's interface that is located on the Lakeland LAN will become the client host's default route:

route add default gw 10.0.0.1

[Exercises]

Complete the following exercises, recording your findings, and the procedures used to obtain them in your log.

Note: Before disconnecting from SOFTICE, be sure to shut your virtual hosts down. This procedure is described in Exercise 1-3: Shutdown the Network. This must be done in order to conserve system resources on the SOFTICE cluster.

Exercise 9-1: Subnet and Configure Routing for the Two Locations Network

1. The Two Locations Network has been assigned the 172.16.0.0/255.255.255.0 IP block. Create a new copy of the Two Locations Network configuration file, then reconfigure each host appropriately. Work with the following assumptions:

• All WANs (Wide Area Networks) have two hosts
• The LANs (Local Area Networks) require the ability to support at least 50 hosts each

2. Configure routing so that all hosts have networking connectivity to each other.

3. Verify connectivity between all hosts.

4. Copy the full text of your modified Two Locations Network configuration file into your log.

Exercise 9-2: Subnet and Configure Routing for the Three Locations Network

1. The Three Locations Network has been assigned the 10.100.4.0/255.255.254.0 IP block. Create a new copy of the Three Locations Network configuration file, then reconfigure each host appropriately. Work with the following assumptions:

• All WANs (Wide Area Networks) have two hosts.
• The Tampa LAN (Local Area Network) must be capable of supporting at least 200 hosts
• The Lakeland and Orlando LANs (Local Area Networks) each require the ability to support at least 60 hosts

2. Configure routing so that all hosts have networking connectivity to each other.

3. Verify connectivity between all hosts.

4. Copy the full text of your modified Three Locations Network configuration file into your log.

References