Module 2 - Design the Network Structure

Section 4 - Design a Network-Layer Addressing and Naming Model

Virtual University: Solution

• Virtual University's Class B network number 172.16.0.0 can be divided as follows:

 
• 172.16.0.0 for the backbone area
• 172.16.64.0 for the North Campus
• 172.16.128.0 for the Central Campus
• 172.16.192.0 for the South Campus

• The first two bits of the third octet can be used to identify the area that supports route summarization. For example, a border router at the North Campus can advertise all 40 network numbers with one route, 172.16.64.0/18 (18 bits are relevant, in other words, a subnet mask of 255.255.192.0).

 
• The next six bits of the third octet can be used to identify the 40 networks that will work even when there are 60 networks five years from now.

 
• The last octet can be used to identify the 150 nodes on each network that will work even when there are 200 nodes per network. This solution means that the internal campus routers and end-user nodes support a simple 172.16.x.0/24 configuration, in other words, a 255.255.255.0 subnet mask. This is an attractive solution for Virtual University, which requires simplicity because of its AppleTalk heritage.

 
• Because of Virtual University's history, you should recommend dynamic addressing for the end nodes. The network administrators should install DHCP servers on each of the internal campus networks.

• Virtual University is using a private IP network number, 172.16.0.0. In order to reach the Internet, the network administrators should install a gateway, such as Cisco's PIX Firewall product, which will give Virtual University security features in addition to the ability to use a private network number.

• To name the routers, servers, and end nodes at Virtual University, DNS servers should be installed and configured. To name the routers and servers, use a naming scheme that requires the name to start with North, South, Central, or Back (for Backbone) to facilitate troubleshooting. The router names could have a number suffix also that identifies the network number. The servers should have a non-numeric suffix that is meaningful to users.

 
• The users should be encouraged to name their stations with names that will facilitate troubleshooting, for example, last name-first name. However, because the users are students and professors, creative solutions should be tolerated also! Use Cisco's DNS/DHCP Manager to synchronize DNS names with dynamically assigned IP addresses.

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