CCNA Cisco Certified Network Associate Study Guide - FTP Server

396 Chapter 8 � Configuring Novell IPX
Encapsulation
Encapsulation, or framing, is the process of taking packets from upper-layer
protocols and building frames to transmit them across the network. As you
probably recall, frames live at layer 2 of the OSI model. When you’re dealing
with IPX, encapsulation is the specific process of taking IPX datagrams
(layer 3) and building frames (layer 2) for one of the supported media. We’ll
cover IPX encapsulation on the following physical networks:
� Ethernet
� Token Ring
� FDDI
Why is encapsulation significant? Well, for the very good reason that Net-
Ware supports multiple, incompatible framing methods, and it does so on
the same media. For instance, take Ethernet. NetWare has four different
frame types to choose from, depending on your needs (see Table 8.1), and
each one of those frame types is incompatible with the other ones. It’s like
this: Say your servers are using Ethernet_802.2 and your clients are configured
for Ethernet_II. Does this mean you don’t have to worry about anything?
Not necessarily. If they’re communicating with each other via a router
that supports both frame types, you’re set. If not—you’re cooked—they just
won’t talk! When configuring any IPX device (including a router) on a network,
the frame type has to be consistent for things to work.
TABLE 8.1 Novell Ethernet Encapsulations
NetWare Frame Type Features
Ethernet_802.3 Default up to NetWare 3.11
Ethernet_802.2 Default since NetWare 3.12
Ethernet_II Supports both TCP/IP and IPX
Ethernet_SNAP AppleTalk, IPX, and TCP/IP