Networking 101

Copyright Priscilla Oppenheimer

Lab 8 IP Addressing and Subnetting

Scenario

You are a senior network administrator who works for a large company. The network engineers at corporate headquarters have declared that you can no longer use all the IP addresses that you are currently using because they are running out of addresses. They have given you the job of redesigning your IP addressing with just one network number: 192.168.100.0. All the router interfaces and hosts will have an address on the 192.168.100.0 network. You will need to subdivide this number for your subnets.

Designing an Addressing Scheme

How many distinct networks do we currently have in the lab? __________________
How many hosts do we want to allow per network? __________________________
What subnet mask should we use to accommodate that number of networks and hosts per network?
1. Subnet mask in slash notation _________________________________________
2. Subnet mask in binary _______________________________________________
3. Subnet mask in decimal ______________________________________________
Which number should we use for each network? We will work this out on the board together.
Fill in the following chart for the last octet (byte). (All addresses will start with 192.168.100.0, so there's no need to show the first three octets.)

Binary and Decimal Subnet Numbers

Subnet	Subnet bits in binary	First host in binary	Last host in binary	First host in decimal	Last host in decimal
0
1
2
3
4
5
6
7

Configuring Addresses

Power on the workstations, routers, switches, and firewalls.
Configure the workstations for the new IP addressing information.
1. On Windows, use the Network Connections Control Panel.
2. On Linux, use yast.
To configure the routers and firewalls for the new IP addressing information, start a HyperTerminal session.
Type enable (followed by Enter). Type the enable password, provided by the instructor.
Type configure terminal, which means you are configuring the device from a terminal. (Your PC acts as a terminal.)
On the routers:
1. Type interface and the interface type and number, for example interface fa0 or interface fa0/0. Press Enter.
2. Type the IP address and subnet mask using the ip address <address> <mask> command. Press Enter.
3. Be sure to do all interfaces.
On the switch:
1. Type interface vlan 1. Press Enter.
2. Type the IP address and subnet mask using the ip address <address> <mask> command. Press Enter.
On the PIX firewall:
1. Type ip address inside followed by the IP address for e1 and the subnet mask. Press Enter.
2. On PIXC type ip address outside followed by the IP address for e0 and the subnet mask. Press Enter. (There's no need to change the outside interface on PIXB.)
Type exit to get out of configuration mode.
Test the new IP addresses using Ping.
If you can ping other devices in the lab, continue to the next set of steps. Otherwise do some troubleshooting. Ask for help if you need it.

Routing Steps

Most of the routing steps that we did in last week's lab are still valid. (Do you remember last week? :-) The "real" routers use the Open Shortest Path First (OSPF) routing protocol which is a dynamic routing protocol, so they will automatically adapt to our addressing changes, with a couple exceptions. The PIX, not being a real router, can only use default and static routes, so we need to enter those. Likewise, the switch needs to know the new address of its default gateway.

On the switch:
1. Go into config mode, and then use the following command:
2. ip default-gateway <address of the gateway>
3. For the address of the gateway, use the fa0/0 address of one of the 2600 routers.
4. Test your change by seeing if you can ping the switch or Telnet to it from a PC.
On the routers:
1. Go into config mode and enter the following command:
2. ip route 0.0.0.0 0.0.0.0 <address of next-hop router>
3. For the address of the next-hop router:
  1. On the 2600s, use the inside (e1) address of PIX B.
  2. On the 1700s, use the s0/0 address of your local 2600 router.
4. On the 1700A router, configure a static route to the PIX-only-attached extranet.
  1. ip route <extranet network number> <mask> <next hop address>
On the PIX firewall:
1. Firewalls don't usually run a routing protocol. They just send all traffic to a "real" router. So, on the PIX firewalls, you need to configure a default route. PIX B will also need a set of static routes. Get into config mode, and then use the following commands:

Reflection

What were the work goals of this project? (Please write this as if you were writing a work status report. In other words, write the project goals, not the learning objectives.)

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What problems did you encounter? ___________________________________________________________________________________________________________

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What concerns do you have for the future for this network? Assume that you and your co-workers will now have the job of operating and monitoring this new "real-life" network. Based on your experiences setting it up and any problems encountered, what will you be keeping an eye on? What problems may occur?

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