Updating servers with a new network operating system can be troublesome enough without having to consider a change of network protocol, as well. But if you’re considering an upgrade to NetWare 5.x, you’ll find yourself in exactly this situation because Novell encourages users to move to a pure IP environment. Fortunately, Novell has provided tools that make the process of migrating from IPX to IP relatively simple. In this article, we will look at some of the some of the strategies you can use to make the transition from IPX to IP simple and hassle free.
Why IP?
For many years, IPX has been used on NetWare networks. IPX is routable, simple to configure, and has an easy-to-use addressing structure. But, good though IPX is, the IT industry in general has embraced TCP/IP as its protocol of choice. Novell, rather than battling on with IPX, decided that with NetWare 5.x, it would also encourage people to use TCP/IP rather than IPX.
In fact, NetWare servers have provided TCP/IP functionality for years, but mainly for the support of network services and applications rather than pure server-to-client communication. The difference in NetWare 5.x is that IP is the default protocol for all network services, including core communication services. This core communication uses a system called NetWare Core Protocol (NCP). Support for NCP natively over IP means that NetWare networks can now be made completely IP based; IPX isn’t needed unless backward compatibility is required for legacy applications or network services. The provision of NCP over IP is effectively the last piece in the Novell and IP jigsaw; other services, such as DHCP and DNS, have been in place for a number of years.
The Compatibility Mode Driver
In many instances, companies will find the transition to a pure IP environment relatively simple. Unless existing applications or network services make calls over IPX, you shouldn’t need to maintain any IPX support. But if you do have network services that require IPX functionality, or you wish to take a phased approach to migrating to IP, Novell provides a service called the Compatibility Mode Driver (CMD) to ease the process. The CMD has both a server and a workstation component.
The CMD is implemented on a NetWare server through the SCMD.NLM module. This module loads automatically if the server is installed with a network interface that has IP–but not IPX–bound to it. By default, the CMD creates a virtual IPX network of FFFFFFFD, but this can be changed to match an existing IPX network number if necessary. The CMD provides a number of functions including the redirection of Service Advertising Protocol (SAP) packets to the Service Location Protocol (see sidebar), as well as encapsulation of outgoing IPX packets. It also performs decapsulation of incoming packets that contain IPX information.
| SLP |
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One of the most significant changes that IP brings to NetWare networks is the introduction of the Service Location Protocol (SLP). On an IPX NetWare network, resources advertise their availability through the Service Advertising Protocol (SAP). In addition to being inefficient in terms of network traffic, SAP’s dependence on IPX meant that Novell had to find a new method of advertising and locating network resources; hence, the introduction of SLP. |
In addition to the server-based element, network clients must also be configured to use a Compatibility Mode Driver on the workstation. The workstation version of CMD performs the same functions as the server driver: encapsulating and decapsulating IPX packets originating from the workstation, and directing SAP traffic to SLP.
The workstation CMD can be installed when the client software is loaded, or you can add it afterward through Control Panel. If you’re adding or updating the client software, be sure to use the IP With IPX Compatibility option, rather than the IP And IPX option during the Protocol Preference section of the set-up. (The IP And IPX option simply installs both an IP and an IPX stack, and does not provide CMD support.) Workstations loaded with the CMD driver must be directed toward a server that is acting as a migration agent. You can enter this information manually through the network properties in Control Panel, or you can distribute it automatically via DHCP.
On both the workstation and the server, removing CMD support is as easy as unloading the driver.
Providing access to IPX-dependent services is one benefit of CMD; but if you’re considering a phased approach to a pure IP environment, CMD’s other functions will be of more interest. By using CMD, it is possible to configure a server to act as a gateway between an IP-only network segment and an IPX-only network segment. In this configuration, known as Migration Agent, the server with CMD running encapsulates and decapsulates packets to and from IPX and IP as required, providing access from all machines, to all machines, regardless of whether IPX or IP is being used. In addition to connecting two separate segments, CMD also makes it possible to have IP-only and IPX-only clients on a single network segment–again, by acting as a gateway between the two protocols.
A further feature of CMD is its ability to be configured in Backbone mode, which allows IPX information to be encapsulated into IP for transmission on links that do not support IPX traffic. This approach lets you use an IP backbone between two remote sites, while preserving the IPX configuration on LANs.
| CrossLinks |
| For more information, visit the NetWare 5.x homepage. |
Summary
CMD gives those introducing a pure IP environment the luxury of knowing that you don’t need to adopt an all-or-nothing approach to migration. Even if you only use CMD as a transition measure, the ease with which it can be configured and removed makes it a key tool during this process. //
Drew Bird (MCT, MCNI) is a freelance instructor and technical writer. He has been working in the IT industry for 12 years and currently lives in Kelowna, BC., Canada. You can e-mail Drew at drew.bird@tecmetrix.com.
