User guide

436
pmp-0229 (Mar 2013)
Filtering Protocols and Ports Securing Your Network
Port Filtering with NAT Enabled
Where NAT is enabled, you can filter only the three user-defined ports. The following are
example situations in which you can configure port filtering where NAT is enabled.
• To block a subscriber from using FTP, you can filter Ports 20 and 21 (the FTP ports) for both
the TCP and UDP protocols.
• To block a subscriber from access to SNMP, you can filter Ports 161 and 162 (the SNMP
ports) for both the TCP and UDP protocols.
NOTE: In only the SNMP case, filtering occurs before the packet interacts with the protocol
stack.
Protocol and Port Filtering with NAT Disabled
Where NAT is disabled, you can filter both protocols and the three user-defined ports. Using the
check boxes on the interface, you can either
• allow all protocols except those that you wish to block.
• block all protocols except those that you wish to allow.
You can allow or block any of the following protocols:
• PPPoE (Point to Point Protocol over Ethernet)
• Any or all of the following IPv4 (Internet Protocol version 4) protocols:
o SMB (Network Neighborhood)
o SNMP
o Up to 3 user-defined ports
o All other IPv4 traffic (see Figure 151)
• Uplink Broadcast
• ARP (Address Resolution Protocol)
• All others (see Figure 151)