Enterasys Networks 6000 - Manual (Page 209)

FDDI Management
6-18 Configuring FDDI Frame Translation Settings
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 Enterasys (and many other vendor’s)
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 802.2, FDDI SNAP
(generally used when bridging to an AppleTalk environment on an FDDI ring), or FDDI
MAC (the default option, which translates the frame into an FDDI MAC frame – which
will not recognized as a data frame on an FDDI ring, but will be recognized by a Enterasys
Ethernet/FDDI bridge).