Global Technology Associates GBWA200501-01 Re-configuring Your Computer, Accessing the Firewall

28 GB-Ware Firewall Product Guide

Using CIDR-based or Slash (/) Notation

CIDR (Classless Inter-Domain Routing) aggregates routes so that one

IP address represents thousands served by a backbone provider. GNAT Box System Software uses CIDR-based notation as the default for subnet masks, instead of dotted decimal (e.g. 255.255.255.0) notation.

Instead of the fixed 8, 16 and 24 bits used in dotted decimal Class A, B, or C net masks, CIDR-based notation can further divide the network into subnets by using bit masking of any number from 1 to 32 to determine network class (/32 representing one IP address). For example, the CIDR address 204.12.01.42/24 indicates that the first 24 bits are used for the network class ID. The /24 mask includes 254 hosts on the network, and is equivalent to 255.255.255.0 in dotted-decimal notation.

Calculate a CIDR-based notation net mask by converting the dotted decimal net mask to binary and count the ones. For a Class C network, the dotted decimal net mask is 255.255.255.0. The binary notation of that net mask is 11111111.11111111.11111111.00000000. There are 24 ones, so the CIDR notation would be /24. Using a 255.255.255.240 net mask, the binary repre- sentation would be: 11111111.11111111.11111111.11110000. The notation would be /28.

You may also enter a host address that is defined by not including a bit mask (e.g. 192.168.123.1). This is equivalent to a /32 bit mask. To enter a range of addresses, use a hyphen (-) between the two extremes of the range (e.g. 192.168.123.0-192.168.123.255).

Dotted decimal may still be used by entering the dotted decimal net mask after the forward slash.

Re-configuring Your Computer

If you temporarily changed your computer’s network configuration to connect to the firewall, restore the original configuration now. If you formed a temporary peer network during network configuration, disassemble it now; reconnect your computer and the firewall to your network. Now your computer and firewall should both be members of your network. Reboot your computer if necessary to affect the network configuration change.

Accessing the Firewall

Access the firewall using the IP address you assigned to the protected network.

The firewall should now be active and functioning in default security mode (all internal users are allowed outbound and no unsolicited inbound connec- tions are allowed). You can now perform any additional configuration tasks, including changing the administrative password.