3. Configuring the DSL Router3-12 November 2003 6300-A2-GB20-10Ethernet Type FilteringEthernet Type filtering (Ethertype) does not apply when the DSL router is inrouter-only mode. By default, Ethertype filtering is disabled on the Hotwire DSLcard for the DSL router. If enabled, separate Ethertype filters are applied to theEthernet and/or DSL interface with one filter per interface direction. There is amaximum of 16 rules per list. Each rule access list allows filtering of a singleEthertype or a range of Ethertypes.MAC frames can be filtered based on the: SNAP Ethernet field in the 802.3 header. Protocol type field in the DIX Ethernet header.For Ethertype filters, the rules are applied in the order in which they wereconfigured. For additional information about Ethertype filters, refer to the HotwireMVL, ReachDSL, RADSL, IDSL, and SDSL Cards, Models 8310, 8312/8314,8510/8373/8374, 8303/8304, and 8343/8344, User’s Guide.Land Bug/Smurf Attack PreventionLand Bug and Smurf Attack prevention are enhanced firewall features providedby the router. Land Bug – The router drops all packets received on its DSL or Ethernetinterface when the source IP address is the same as the destination IPaddress. This prevents the device from being kept busy by constantlyresponding to itself. Smurf Attack – The router does not forward directed broadcasts on its DSLand Ethernet interfaces, or send an ICMP echo reply to the broadcastaddress. This ensures that a legitimate user will be able to use the networkconnection even if ICMP echo/reply (smurf) packets are sent to the broadcastaddress.
