Cabletron Systems SmartStack STS16-20R, Installation And User Manual

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SmartStack STS16-20D/STS16-20R Token Ring Switches Installation and User Guide Preparing for Installation
You can also use the NET 18K dialog box in the HP OpenView application. This
dialog can display all the hardware modules. Note that the SSIM-H2-02 Fast
Ethernet - Translational Switch SmartStack Interface Module might display 1,500
bytes, but this does not prevent the stack from running 18 KB.
For information on how to upgrade your stacker link modules or ATM uplinks that
currently do not support 18 KB frames, please contact your dealer or your local
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.
IEEE 802.1D Spanning Tree
When the IEEE 802.1D Spanning Tree Protocol is active, a port within that
spanning tree domain will require several seconds to make the transition from the
blocking state to the forwarding state, from the time the port is initially activated
(for example, joins an existing ring or activates a dedicated link).
Some client or server applications may attempt to establish session activity during
this time, resulting in error messages indicating a connection failure. These
applications should be configured to wait at least thirty seconds after the LAN link
has become active, before attempting to establish session activity. Modifying the
802.1D spanning tree default parameters can reduce this delay. If STP is enabled
on a dedicated port (FDX) and a station is attached, it takes at least 30 seconds for
the port to do the transition DWN
→ → → →
LSN
→ → → →
LRN
→ → → →
FWD. IPX clients and server
stations may give up before the transition is done. This means that the first many
connection attempts are lost. STP should not be enabled on ports that are intended
for dedicated stations. This problem does not occur on shared media, because the
port will stay attached to the hub even though all stations have closed.
Another reason for not enabling STP for dedicated stations is, that the whole
network will go into
Topology Change state each time a station opens or closes.
This will cause the whole network to use short aging timers, which means that all
address tables will be cleared. This can lead to many unknown station broadcasts
before the tables converge again. Note that a port or CRF that is manually forced to
either FWD or BLK state, is not participating in the spanning tree protocol. If a port
or CRF is changed from
Auto (the default) to FWD/BLK , it is the network
administrator’s responsibility that no loops are created from this port(s) to other
parts of the network.