Reference Guide for the Model RT311 and RT314 Internet Access Gateway Routers
Configuring Filters 10-11
Default Filters
The Model RT311 router is preconfigured with the three filters shown in Figure 10-1 on page 10-2
and in this section.
Filter 1: NetBIOS_WAN
The NetBIOS_WAN filter is an IP protocol filter used to prevent the sending of Windows
NetBIOS name service packets to the ISP. The ports used by NetBIOS name service are:
• 137 (TCP and UDP) NetBIOS Name Service
• 138 (TCP and UDP) NetBIOS Datagram Service
• 139 (TCP and UDP) NetBIOS Session Service
This filter is applied in Menu 4.1 - WAN Port Filter as an Output Filter set.
Filter 2: NetBIOS_LAN
The NetBIOS_LAN filter is an IP protocol filter used to block NetBIOS name service requests
from a local PC to the DNS server of the ISP. These requests are UDP packets having a source port
of 137 (NNS) and a destination port of 53 (DNS).
This filter is applied in Menu 3.1 - LAN Port Filter as an Input Filter set.
Filter 3: TEL_FTP_WEB_WAN
The TEL_FTP_WEB_LAN filter is an IP protocol filter used to block Telnet, HTTP, and FTP
requests to the router from the Internet. The filter blocks TCP packets with a destination port of 21
(FTP), 23 (Telnet), or 80 (HTTP).
This filter is applied in Menu 11.5 - Remote Node Filter as an Input Filter set. If you need Telnet or
FTP access to the router from the Internet, you must remove the filter number (3) from Menu 11.5.
To reach Menu 11.5, follow these steps:
1.
From the Main Menu, select Menu 11 - Remote Node Setup
This will display Menu 11.1 - Remote Node Profile
2.
Go to Edit Filter Sets and use the space bar to toggle the value to Yes
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