Controlling the Propagation of Type 20 Packets

Novell Internet Access Server 4.1 enables you to control the propagation of type 20 packets with the Advanced Packet Type 20 Flooding parameter. Type 20 is an IPX packet type that refers to any propagated packet. NetBIOS packets, for example, are type 20 packets.

The Advanced Packet Type 20 Flooding parameter can be set to one of the following options:

• 0 ---Router discards, rather than propagates, any type 20 packet it receives. This option completely disables type 20 packet propagation.

• 1 ---Router receives and propagates type 20 packets through all its interfaces, regardless of whether some of the interfaces are equal-cost routes to the same source.

• 2 ---Router propagates type 20 packets only through interfaces that do not lead back to the source of the packets. For example, if Router A receives a type 20 packet from Router B, Router A forwards the packet only through interfaces that do not lead back to Router B. This is a packet forwarding mechanism known as reverse path forwarding .

  The router does not propagate type 20 packets through the same interface from which it receives them. This is known as split horizon , a technique used with RIP and other distance vector routing protocols.

• 3 ---Router propagates type 20 packets the same way as option 2, but does not forward them across WAN connections.

If you use FILTCFG to configure NetBIOS packet filters, be aware of the following interactions between these filters and the Advanced Packet Type 20 Flooding parameter:

• Setting Advanced Packet Type 20 Flooding to 1 (disabled) overrides the effect of NetBIOS packet filters operating on any network interface.
• Conversely, the action of NetBIOS packet filters on any network interface overrides the effect of setting the Advanced Packet Type 20 Flooding parameter to 2 (enabled).

How to Control Propagation of Type 20 Packets

To configure the propagation of type 20 packets from the server console, enter the following console command:

SET IPX NETBIOS REPLICATION OPTION = [0|1|2|3]

To check the current setting, you can type the command by itself.

To configure the propagation of type 20 packets from NIASCFG, complete the following steps:

1. Load NIASCFG, then select the following parameter path:

   Select Configure NIAS > Protocols and Routing > Protocols > IPX > Expert Configuration Options

2. Select Advanced Packet Type 20 Flooding and select one of the options described previously.

3. Press Esc and save your changes.

4. Press Esc to return to the Internetworking Configuration menu.

5. If you want this change to take effect immediately, select Reinitialize System .

   If you want to configure other parameters, do so now, then reinitialize the system when you are finished.