Many applications in the NetWare
environment use the Network Basic Input/Output System (NetBIOS) request services
from IPX servers. These services include session establishment and termination
and information transfer.
On a NetWare client, a NetBIOS application using IPX broadcasts type 20 propagation packets to all IPX networks in order to get
information about named nodes on the network. NetBIOS uses named nodes for
resources on the network. To communicate with these resources, NetWare clients
need to map these named nodes to IPX addresses.
an IPX broadcast mechanism
to map named nodes to IPX address. As you have seen throughout this book,
Cisco routers block all network layer broadcast packets by default, including
IPX type 20 propagation packets. If a router does not forward any type 20
propagation packets and a NetWare client with an application using NetBIOS needs to traverse the router to obtain
information about a named node on the network, the NetWare client is not able
to communicate with the server.
The IOS interface subcommand ipx type-20-propagation
instructs the router to accept and forward type 20 propagation packets to
other IPX interfaces that also have this subcommand configured. The IOS attempts
to forward the IPX type 20 propagation packets in an intelligent mannersuch
as by not putting the packets on interfaces that route to the original source
Instead of forwarding IPX type 20 propagation
packets to multiple network segments, you can forward these packets to a specific
IPX network address, thereby potentially reducing the number of broadcast
packets sent throughout your IPX network. The IOS global configuration command ipx type-20-helpered enables the forwarding of IPX
type 20 packets to a specific IPX address. The IOS interface subcommand ipx helper-address specifies the IPX address to forward
type 20 packets to. The ipx type-20-helpered
and the ipx type-20-propagation commands
are mutually exclusive. The IOS must either forward type 20 propagation packets
other similarly configured interfaces or forward type 20 packets to an IPX
In the following configuration on the ZIP network, we forward all IPX
type 20 packets on the Singapore router, via interface Ethernet 0, to a specific
IPX server in San Francisco at IPX address aa.0005.0112.0474:
Configuring from terminal, memory, or network [terminal]?
Enter configuration commands, one per line. End with CNTL/Z.
Singapore(config)#interface ethernet 0
config-if)#ipx helper-address aa.0005.0112.0474