Protocol Overview


IPX/SPX (internetwork packet exchange/ sequenced packet exchange) is an OSI Reference model Layer 3 protocol suite used with Novell NetWare for transferring data from servers to clients (you learned about the OSI Reference model in Chapter 2, "Networking Principles"). Like TCP/IP, IPX/SPX is a suite of protocols used for network interactions, such as data transport and routing. IPX/SPX (was developed by Novell for use with the NetWare operating system (version 4 and earlier).

NetWare's IPX/SPX network protocols removed many of the client-configuration issues that were inherent with other legacy protocols. Because of this, the release of version 3.11 quickly earned market share and a great reputation for stability, quick installation, and very low maintenance. In NetWare 5 and 6, IPX no longer is required, but rather is an option. TCP/IP is now the default communications protocol.

In this chapter, you learn about the following protocols:

  • IPX

  • SAP and GNS

  • IPX EIGRP

  • RIP

  • NLSP

IPX

The IPX protocol operates at Layer 3 of the OSI Reference model and can share addressing schemes with the IP protocol. This sharing capability makes IPX easy to configure and administer in the network. Just like an IP address, an IPX address is divided into a network identifier (which is 4 octets) and a node (host) address. The node address is combined with the physical MAC address of the network interface card (NIC) located inside the node. Figure 6.1 shows how Novell NetWare protocols including IPX match up to the OSI Reference model.

Figure 6.1. The Novell NetWare protocol stack compared to the seven-layer OSI Reference model.

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IPX addresses can be found in several formats, but hexadecimal is the most common format. A hexadecimal address of 0000018A.0000.834A.AD66, for example, can be broken down into two parts . The first part consists of the 8 hexadecimal digits, 0000018A, and indicates the network the node resides in. The other 12 hexadecimal digits, 0000.834A.AD66, indicate the node address. Most of the time, when you see the network portion of the address, the 0s preceding the network number are dropped. Therefore, the full IPX network address, including the network and node, would appear as 18A.0000.834A.AD66.

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Hexadecimal is a number representation using the digits 0-9, with their usual meaning, plus the letters A-F, which represent hexadecimal digits with values of (decimal) 10 to 15. The rightmost digit counts ones, the next counts multiples of 16, then multiples of 256, and so on.


IPX Encapsulation

NetWare uses encapsulation, as well as a framing method, to add an IPX datagram at Layer 3 to an appropriate Layer 2 frame. An important piece of knowledge in troubleshooting Novell is the framing process and how it relates to Ethernet, token ring, and Fiber Distributed Data Interface ( FDDI ) physical topologies.

There are several different IPX frame types and it is possible to set the wrong frame types for the network. When an IPX frame type mismatch exists in the network, the IPX networked components cannot communicate, because this situation is somewhat similar to two people trying to communicate in two different languages without a translator. The following are the five Ethernet IPX frame types (the Cisco identifier name that is used to set the frame type is in parentheses):

  • Ethernet_802.3 (novell- ether ) ” The default IPX frame type up to NetWare version 3.11. This version supports only IPX and the Ethernet physical media.

  • Ethernet_802.2 (sap or iso1) ” The default IPX frame type beginning in NetWare version 3.12. This frame type is supported on multiple physical media types, including Ethernet, FDDI, and token ring, and is recommended for networks with multiple media types.

  • Ethernet_II (arpa) ” This frame type supports TCP/IP and IPX. An ether type value is placed after the source MAC address to identify the protocol. The ether value for IPX is 8137, and IP is 0800.

  • Ethernet_SNAP (snap) ” This frame type supports AppleTalk, IPX, and TCP/IP on multiple physical media types, which are token ring, Ethernet, and FDDI, using a SNAP header.

  • Token Ring (token) ” This frame type supports only token ring traffic for IP, IPX, or Novell Layer 3 traffic.

Depending on the Cisco IOS you are using, you can view the configuration and frame types configured on the router by using the following commands:

  • write terminal (IOS version 11.1 or later)

  • show running-config (IOS version 11.2 or later)



CCNP CIT Exam Cram 2 (642-831)
CCNP CIT Exam Cram 2 (Exam Cram 642-831)
ISBN: 0789730219
EAN: 2147483647
Year: 2003
Pages: 213
Authors: Sean Odom

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