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FDDI Concepts
US7070447-001, Rev 01
12-5
Draft Level—Hitachi Confidential
Filterin
g
Mode
With FDDI Filtering, packets between FDDI-native devices are filtered at the
FDDI Uplink, not at the switch’s bridging table. This method of filtering reduces
the burden on the HiSpeed processor. If the FDDI ring is small and the number of
native FDDI devices is limited, FDDI filtering is recommended. Maximum
number of entries in the FDDI Filtering table is 4096.
Forwardin
g
Mode
With FDDI Forwarding, the MAC addresses of the directly-attached Ethernet
devices are placed into the FDDI forwarding table, then only those FDDI packets
with destination addresses corresponding in the forwarding table are forwarded to
the Ethernet. All other packets are dropped at the FDDI interface, and as a result,
reduce the potential load on the HiSpeed processor. If the FDDI ring is very large
and the number of directly-attached Ethernet devices is limited, FDDI forwarding
should be employed. Maximum number of entries in the FDDI Forwarding table
is 256.
Promiscuous Mode
With FDDI Promiscuous mode, all packets will be received and forwarded to the
FDDI Uplink. This configuration is not recommended as an increased load will
be placed on the HiSpeed processor; thereby dramatically reducing the switch’s
performance.
FDDI Troubleshooting Tips
❒ The FDDI Uplink module must be inserted into the lower PCI slot only.
❒ A multimode fiber (MMF) cable is required for use with the FDDI uplink
module. Each port (A or B) requires a duplex (pair) fiber between two
adjacent HS150s. Do not use a simplex (single) fiber to connect two adjacent
FDDI ports.
❒ FDDI Filtering is the default configuration mode.
❒
With Spanning Tree enabled, verify that a virtual port
’34 FDDIBRG’
is
active and in a Forwarding state.
‘vvp’
or
‘vps 34’
❒ Must be running software version 1.4.4 or later.