H3C Technologies H3C MSR 50 - Manual (Page 9)

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which is collected by the SAP proxy and saved in the server information table in the IPX router for
advertisement to such clients. Because server information is dynamically updated by SAP, clients can
always obtain latest server information.
SAP defines three types of packets, service query, service response, and periodic updates. The following
subsections describe how SAP operates:
NetWare client initialization
When a NetWare client is initializing, it needs to locate a server. To do so, the client broadcasts a get
nearest server (GNS) request. At least one router or server can give a SAP response, which contains
information such as packet type, service type, and server name and address. The NetWare client can
communicate with the server through the IPX address in the response packet.
Because the GNS request is broadcast, the client can only get a response from the server in the local IPX
network.
To locate a server in another network, the IPX router can send a RIP request to get the route to the server,
and send the route and service information to the client. In this way, the client can communicate with a
server in another network.
Periodic update of SAP
A server broadcasts a SAP packet to provide the service name and type, and its IPX address. The IPX
router that receives the broadcast will add the service to the service information database and
periodically broadcast such information in the directly connected networks. The advertisements can thus
flood the entire network.
By default, SAP broadcasts are sent every 60 seconds. Each packet can have up to seven service
information items by default. If a large amount of service information needs to broadcast, the information
can be sent in several packets. For example, 20 service information items can be sent in three packets.
IPX NetBIOS
As a broadcast, a NetBIOS packet is not routable. Therefore, a certain mechanism is needed for the
routing device to forward such packets.
To enable use of network basic input/output system (NetBIOS) in a NetWare environment, Novell uses
a mechanism to set the packet type contained in the IPX header to 20, indicating that the IPX packet is
a NetBIOS packet. A device must forward such packets according to certain rules to make sure NetBIOS
packets are transmitted in the IPX network.
Protocol and standards
• RFC 1132, Standard for the transmission of 802.2 packets over IPX networks
• RFC 1634, Novell IPX Over Various WAN Media (IPXWAN)
Configuring basic IPX
Follow these guidelines when you configure basic IPX:
• The node address specified with the ipx enable [ node node ] command is the global node address,
used by all interfaces but the Ethernet interfaces on the router. If no node address is specified, the
router specifies the MAC of the first Ethernet interface as the global node address. If no Ethernet