Installation; Required Network Preparation - Frame Length Limit - Olicom CrossFire 8600 Manual To Operations

4. Installation

This chapter contains step-by-step instructions for installing, connecting and
verifying that the CrossFire 8600 Token-Ring Switch and/or CrossFire 8605
Token-Ring Fiber Switch is operating properly.

Required Network Preparation - Frame Length Limit

The CrossFire 8600 and the CrossFire 8605 both support a maximum physical
frame length of 18,192 bytes (from the Frame Control (FC) to the Frame Check
Sequence (FCS) characters). This corresponds to a Maximum Transfer Unit (MTU)
of 17,800 bytes.
The default maximum physical frame length of the switch is 4,546 bytes which
corresponds to an MTU of 4,472 bytes. The actual MTU size of a VLAN is
configured in the VLAN Parameter Configuration for TrBRF screen, see
page 92.
The switch truncates frames larger than the configured maximum physical frame
length and adds an abort sequence at the end. Characteristically, if frames are sent
longer than the frame length limit, the abort sequences will be reported as frame
errors by other ring stations.
In a stack of switches, all stacker link modules in the stack must support 18,192
byte frames (18 KB frames) for any switch in the stack to support frames sizes
longer than 4,546 bytes. Additionally, if you are using ATM uplinks, all ATM
uplinks in the switch and in the stack must support 18 KB frames for any switch in
the stack to support frames sizes longer than 4,546 bytes.
To verify that your hardware supports 18 KB frames, view the Module
Information screen, described on page 85. Stacker link modules and ATM uplinks
that do not support 18 KB frames will have the text (4k) displayed immediately
after the hardware revision level.
For information on how to upgrade your stacker link modules or ATM uplinks that
currently do not support 18 KB frames, please contact your Olicom dealer or your
local Olicom representative.
Note: It is most important that you consider the impact of the frame length limit,
and make sure that the workstations and servers in the network have been
configured to use a maximum frame length of equal or less than the switch. If this
is not done you may experience problems after the switch has been installed in the
network.
CrossFire 8600/8605 Token-Ring Switches v. 1.2, P/N: 710001641
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Installation