User manual

Packet Filters 8-11

Specifying the Filtering Action

You can specify the filtering action for each protocol section that

determines whether a packet is accepted or rejected if no match

occurs with any of the rules defined in the section. To do this,

enter one of the following values on a line immediately

following the last rule of the section:

• permit

• deny

For example, the following entry would reject IP packets that

did not match any of the rules defined in the IP protocol section:

IP:

010 ACCEPT src-addr = 128.100.33.1;

020 ACCEPT dst-addr = 200.135.38.9;

030 REJECT tcp-dest-port >= 24;

deny;

Note: If you do not specify a filtering action, the default filtering

action is permit.

Creating Filter Files

You can create filter files using any text editor. Once the file is

created, you use the Trivial File Transfer Protocol (TFTP) to

place the filter file in the NETServer flash memory.

To create a filter file:

Open a new text file. Enter a file descriptor on the first line:

#filter

Enter a file section header followed by a colon for protocol

rules you want to define. For example, if you want to define

IP filtering rules, enter the following section header:

IP:

Note: You can comment a section header out by placing a # sign

before the section header. This is useful if you want to insert a

placeholder for a protocol section you will define in the future.