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IPX defines its own internetwork and intranode addressing. For intranetwork (node) addressing, IPX uses the physical address assigned to the network interface board.
The IPX network address uniquely identifies an IPX server on an IPX network and individual processes within the server. A complete IPX network address is a 12-byte hexadecimal number comprising the following components:
The following is an example of a complete IPX network address:
FEDCBA98 1A2B3C5D7E9F 0453
Each number in an IPX address is contained in a field in the IPX header and represents a source or destination network, node, or socket. The network number is used only for Network-layer operations, namely routing. The node number is used for local, or same-segment, packet transmission. The socket number directs a packet to a process operating within a node.
For more information about each address component, refer to
The IPX network number is the 4-byte hexadecimal address that serves as the basis for IPX packet routing. Each network segment on an internetwork is assigned a unique network number. NetWare routers use this number to forward packets to their final destination network.
An IPX network number can contain up to eight digits, including zeros. (Leading zeros are usually not displayed.) For example, 0xFEDCBA98, 0x1234567D, and 0xC7 are all valid network numbers.
With the fast setup feature available from NIASCFG, the routing software can automatically detect the network number and data-link frame type used on an IPX network. After you configure a board and select a driver during the initial router configuration, the router sends a RIP all routes request packet to the network. From the responses it receives, the router determines the network number and frame type it needs to use.
The destination network of an IPX packet is typically an IPX network to which a unique network number has been assigned. However, three network numbers---0x0, 0xFFFFFFFF, and 0xFFFFFFFE---are reserved and cannot be used to identify a specific network. These numbers have the following meanings:
0x0 ---Represents the local network segment. If a router receives a packet whose destination network number is 0, the packet's source and destination nodes are attached to the same segment.
0xFFFFFFFF ---Represents an all routes request between NetWare routers. If a router receives a packet whose destination network number is FFFFFFFF, it sends all the routes it knows about to the requesting router.
0xFFFFFFFE ---Represents the default route . This is an advertised destination to which IPX packets with unknown destination networks are forwarded.
With NetWare routing software, a router that receives an IPX packet with an unknown destination network can do one of two things: If another router on the network is advertising 0xFFFFFFFE, the router forwards the packet to that router. If 0xFFFFFFFE is not advertised on the network, the packet's destination remains unknown and the router discards the packet.
Both RIP and NLSP have been modified to recognize 0xFFFFFFFE as the default route. On a RIP network, the default route is typically advertised by a RIP router that connects the LAN to a larger network infrastructure, such as a corporate backbone or transit LAN .
The routing software cannot advertise the default route dynamically, but you can configure the router to advertise it as a static route . To read about static routes, refer to Static Routes and Services.
NetWare 3 servers and NetWare 4 servers have an additional identifier called an internal network number. This is a unique hexadecimal number between one and eight digits that is assigned to the server at installation. The internal network is a logical network that NetWare uses to advertise services and route IPX packets to the physical networks attached to the server.
The internal network number overcomes some routing and connectivity limitations inherent in NetWare 2. These are summarized in the following paragraphs.
A NetWare 2 server selects a primary interface and advertises its services as reachable through that interface. On a network with more than one server, packets might travel an extra hop to reach their destination.
A NetWare 2 server loses network connectivity if its primary network interface board fails, even if the server has Network-layer connectivity through another interface. Consider a NetWare 2 server with connections to two networks. The server advertises its services through the primary interface attached to one of the networks. If that interface fails, workstations attached to the server through the second network might not be able to log in to the server.
The node number is the 6-byte hexadecimal address that identifies a device on an IPX network. This device can be a file server, router, workstation, or printer. The node number is identical to the physical address assigned to the interface board that connects the device to the network.
The IPX header contains a Destination Node field and a Source Node field. These fields contain the same destination and source node addresses found in the MAC header. A NetWare workstation, for example, uses the destination node address to locate and forward packets to another workstation on the same network segment.
IPX requires the node number to be unique only within the same IPX network. For example, a node on network FEDCBA98 can use the number 1A2B3C5D7E9F, and a node on network 1234567D can also use the number 1A2B3C5D7E9F. Because each node has a different network number, IPX recognizes each node as having a legitimate, unique address.
The socket number is the 2-byte hexadecimal number that identifies the ultimate destination of an IPX packet within the node. This destination is actually a process ---such as routing (RIP) or advertising (SAP)---that operates within the node. Because several processes are typically operating at any given time, socket numbers provide a type of mail slot by which each process can identify itself to IPX.
A process that must communicate on the network requests that a socket number be assigned to it. Any packets that IPX receives that are addressed to that socket are passed to the process. Socket numbers provide a quick method of routing packets within a node.
Table 2 lists some socket numbers and processes used in the NetWare environment.
Table 2. NetWare Socket Numbers and Processes
| Socket Number | Process |
|---|---|
0x451 |
NCP |
0x452 |
SAP |
0x453 |
RIP |
0x455 |
Novell NetBIOS |
0x456 |
Diagnostics |
0x9001 |
NLSP |
0x9004 |
IPXWANTM protocol (For information about IPXWAN, refer to IPX Operation over WAN Links.) |
Socket numbers between 0x4000 and 0x7FFF are dynamic sockets; these are used by workstations to communicate with file servers and other network devices. Socket numbers between 0x8000 and 0xFFFF are well-known sockets; these are assigned by Novell to specific processes. For example, 0x9001 is the socket number that identifies NLSP. Software developers writing NetWare applications can contact Novell to reserve well-known sockets.
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