Plan a TCP / IP network infrastructure strategy. In this section, we look at what you need to know to analyze IP addressing requirements and how to plan a TCP/IP-based network strategy. If you think about the exam objective, what comes to mind? This would be a scenario-based discussion, much like the ones we had earlier. For instance, if you were to analyze requirements for a network infrastructure, you would need to use every skill taught to you since starting this chapter. Let's look at a sample situation: You are the administrator of 300 Windows XP Professional workstations and a server farm consisting of 25 Windows Server 2003 systems. You need to develop an IP addressing scheme to assign IP addresses to all 300 Windows XP workstations and all 25 servers, set up Internet Access, and set up business-to-business connections or remote sites. Sounds like a lot of work, doesn't it? Handling this situation really isn't too bad, so let's break down what you may need to know: -
You need to set up TCP/IP, so you start by picking an IP range that works for you. You may not have the flexibility of picking a brand new one (a network specialist within your group may assign it if you do not manage addresses), so let's say the corporate office assigns the two class C addresses 10.10.1.0/24 and 10.10.2.0/24. This assignment gives you more than 500 addresses you can use. -
Next, you need to set up a topology map like the one shown in Figure 2.4. Such a map will most likely be provided for you in the exam, but knowing how to create one solves two problems: passing the exam and working on the job. Remember, exam questions don't come up on the job; real-world experience does, so make this topology map as if you were going to see it in the actual question. Figure 2.4. Planning a complex IP environment.  -
After laying out a map, you can assign the IP addresses. First, you need to assign IP addresses to the user LAN. Because they are all connected to the Layer 3 switch in the middle of the network topology map, you can assign a set of Virtual LANs (VLANs). A VLAN is used to logically segment the network into different subnets for security and manageability. You can either use this approach or make a DHCP super scope of two subnets. Either way, make sure that you have enough IP addresses to provide to all your hosts . Take into account that you will most likely have closet switches, printers, or other devices that may also need to utilize an IP address. -
Next, you should make sure you have a default gateway. Because the Layer 3 switch is also a router, you can make it the default gateway for your network. -
Next, you can assign IP addresses to your servers. You should assign static IP addresses to your servers, printers, and any other resource that will not change. Say you have a proxy server with an IP address of 10.10.1.40. If DHCP somehow gives it another IP address when its leases expires , you need to change all your client assignments. This is something you would never do, so make certain that you assign your resources static IPs. -
Next, make sure that the Layer 3 switch has a route over to the Frame Relay Network, as well as the segment where your Internet access router is. -
Finally, make sure that you have an IP helper address (better known as a DHCP relay agent) configured on your router because, by default, a router does not pass a broadcast across. Therefore, you would have to make sure that your users in the LAN can access and get DHCP addresses from the server farm where the server is located. That's it! You have analyzed a problem and set up a basic IP addressing solution. Now you can get your network up and running. Planning an IP Configuration Strategy For the final step, you need to consider how you will lay out your IP configuration strategy. Because every computer on your network needs to be able to connect via an IP address, you must know how to get each one an IP address if you do not have addresses set statically. A DHCP server dynamically assigns addresses from a manually designated range of addresses called a scope that you predetermine when you deploy your DNS server. Because we already discussed static assignments, let's look at one last option that you may come across and will most likely be tested on during the 70-293 exam. EXAM TIP APIPA Automatic Private IP Addressing (APIPA) is a feature that allows DHCP clients to automatically configure themselves with an IP address and subnet mask when a DHCP server isn't available. The IP address range that APIPA uses is from 169.254.0.1 to 169.254.255.254. When the DHCP server is available, the client can switch back to DHCP.
Automatic Private IP Addressing (APIPA) allows a workstation that cannot reach a DHCP server to assign its own IP address so that it can participate on a network. APIPA uses a range from 169.254.0.1 to 169.254.255.254. This is a great strategy if you do not have any other IP addresses on the network. This is true because the workstations can configure themselves, but, most times, this strategy proves to be useless and only gives you a clue that for some reason this workstation cannot get an IP address from the DHCP server. In any case, make certain that you remember this range and what APIPA is used for. |
