Catholic Education Ministries

Why so many numbers?

There are two sets of numbers (IP addresses) for every school. One set belongs to your internet provider (WAN). A second set is specific to your school (LAN).

The school's firewall/router manages the flow of information between the internet (WAN) and the school's network (LAN). The firewall/router is the only device that has an identiy on both the internet (WAN) and the school's network (LAN). Thus, all communication between the two networks must be handled (routed) by the firewall/router.

Numbers on the school's network (LAN)

IP address

Every device connected to the school's network has a unique IP address. Sample: 172.22.21.209

Subnet Mask

Although cryptic, this number identifies how many potential IP addresses could exist on school's network. Sample: 255.255.255.0

Router (or Gateway)

This is the IP address of the school's firewall/router. Sample: 172.22.21.1

DNS Servers (or Name Server addresses)

These are the IP addresses of the Internet Service Provider's DNS servers (internet phone books), that allow internet domain names to be converted to numberic IP addresses. (Some schools establish their own private DNS server.) Sample: 199.199.220.2 and 199.199.220.5

Numbers of the Internet Service Provider (WAN)

IP address

Every customer connected to the internet has a unique IP address. Sample: 199.199.220.192

Subnet Mask

Although cryptic, this number identifies how many potential IP addresses could exist on your Internet Service Provider's network (or a portion thereof). Sample: 255.255.252.0

Router (or Gateway)

This is the IP address of your Internet Service Provider's router. Sample: 199.199.220.1

DNS Servers

These are the IP addresses of the Internet Service Provider's DNS servers (internet phone books), that allow internet domain names to be converted to numberic IP addresses. Sample: 199.199.220.2 and 199.199.220.5

Assigning IP addresses: Static versus Dynamic

Every device (computer, printers, etc) connected to the school's network needs to be assigned an IP address. The school's technology leader (network administrator) is responsible for managing this task.

There are two common methods of assigning IP addresses . . .

• Static/Manual: The technology leader maintains a typed list of all devices and the IP address (s)he has assigned to those devices. Additionally, the technology leader has manually entered that IP address into each of the respective devices.
• Dynamic/DHCP: The technology leader has turned over the task of managing IP addresses to software (DHCP service) that resides on either the server or the firewall/router. Each device looks to the DHCP service to find out what its IP address should be. The IP addresses are assigned at random and can frequently change.

In reality, few schools uses just the static/manual method or just the dynamic/DHCP method. Some devices (server, printers) require static IP addresses. Some software technologies (NetBoot/NetRestore) require that DHCP service be available for occasional usage. Thus, a combination of the two methods is common.

The workstations (student and employee computers) can use either method. It is up to the technology leader to decide if workstations should use the static/manual method or the dynamic/DHCP method.

Benefits of dynamic/DHCP: Dynamic IP addresses are easy because there is less configuration for the equipment. New computers can automatically load the appropriate network settings (including an IP address) from your DHCP server.

Benefits of static/manual: Although there is a lot of typing to configure a static IP address on a device, it allows that device to have the same IP address forever. During troubleshooting and while reviewing network logs, the technology administrator can quickly identify the source of trouble.

Declaring static/manual IP Addresses

If a device such as a server or printer needs a static IP address, do not randomly select an IP address. If a list of available IP addresses does not exist, it is necessary to review the firewall/router's configuration and create appropriate documention.

Documentation

Clearly document (in a binder) all IP addresses for both the school's network (LAN) and the Internet connection (WAN).