Implementing The Filter; Figure 9-5. Menu 21 - Filter Set Configuration - NETGEAR RT338 Reference Manual

Reference Guide for the Model RT338 ISDN Router

Implementing the Filter

Now you can proceed to define a call filter to block the three NetBIOS service ports.
To define a call filter:
Go to Menu 21 - Filter Set Configuration
1.
Menu 21 - Filter Set Configuration
Filter
Set # Comments
------ -----------------
1 netbios
2 _______________
3 _______________
4 _______________
5 _______________
6 _______________
Enter Filter Set Number to Configure= 1
Edit Comments= netbios
Press ENTER to Confirm or ESC to Cancel:
Figure 9-5. Menu 21 - Filter Set Configuration
Next, define the filter rules.
2.
You want your filter to ignore (drop) UDP and TCP packets originating from ports 137, 138,
and 139. Because each protocol/port combination must be specified as a separate rule, there
are six rules. Each filter set contains six rules, so you fill one entire set. Begin with rule 1, as
illustrated in Figure
Set Active to Yes, and specify the IP Protocol as 17, which is the UDP Protocol number
3.
(in decimal) from the Assigned Numbers RFC.
9-10
Filter
Set #
------
7
8
9
10
11
12
9-5.
(Figure 9-5), and choose a name and filter set.
Comments
-----------------
_______________
_______________
_______________
_______________
_______________
_______________
Configuring Filters