Configuring FDDI Frame Translation Settings 6-17

FDDI Applications
There is no FDDI equivalent for Ethernet 802.3 Raw frames or Ethernet II frames.
Enterasys’ Ethernet/FDDI bridges will automatically translate Ethernet II frames
into FDDI SNAP frames, by identifying it as a SNAP frame in the LLC header,
and inserting a SNAP header with the Ethernet Type field.
By default, Enterasys’ Ethernet-to- FDDI bridges will translate an 802.3 Raw
frame into an FDDI MAC frame – although you can use the FDDI Frame
Translation window to alter the default translation. The FDDI MAC frame is an
FDDI frame type that is defined for internal use by the MAC layer, and which is
not passed to higher layer communications protocols on the datalink layer. Any
802.3 Raw frame translated into FDDI MAC will be recognized as such by other
Ethernet/FDDI bridges inserted in the ring, and will be forwarded onto the target
Ethernet segment as an 802.3 Raw frame.
FDDI Frame Translation Options
The FDDI Translation window lets you select which translation methods you
want enforced when translating frames from an FDDI frame format into an
Ethernet frame format, and when translating Ethernet Raw frames into FDDI
frames. It also lets you choose whether to allow fragmentation of IP datagrams
into smaller datagrams, and enable or disable the Auto Learn Novell Frame
Translation option.
To set frame translation parameters:
1. Click on the selection boxes of interest (described below), and select the
desired translation options.
2. Click Apply to save your new frame translation settings at the device, or click
Cancel to restore the last saved options.
IP Fragmentation
The IP Fragmentation selection box lets you specify frame fragmentation
parameters. FDDI traffic may need to be split, or fragmented, into two, three, or
four smaller frames to be successfully transmitted on an Ethernet network. For
fragmentation to be allowed, the frame must be an FDDI SNAP frame with an
OUI of 00-00-00 (indicating TCP/IP) and an IP protocol type identifier (08-00).
Possible options are Enabled (allow IP fragmentation – the default) or Disabled
(prevent IP fragmentation, and discard frames over 1518 bytes).
Translate all Non-Novell FDDI SNAP frames to
This selection box lets you set the translation parameters for non-Novell FDDI
SNAP frames. Possible options are Ethernet II (the default, which you should use
when bridging to most TCP/IP networks) or Ethernet SNAP (which you should
use when bridging to an AppleTalk environment on Ethernet).
Translate all Ethernet Raw frames to
This selection box lets you set the translation parameters for Ethernet Raw
(Ethernet 802.3) packets. Ethernet Raw frames are used on networks running the
IPX protocol on Novell NetWare versions prior to 3.12. Possible options are FDDI