Restrictions - Cisco Catalyst 5000 Series Manual

Restrictions

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The Cisco implementation of LANE over IEEE 802.5 uses existing terminology and configuration options
for Token Rings and provides for the IEEE 802.5 transport of Token Ring frames across an ATM switching
fabric.
Restrictions
Before you implement Token Ring LANE, be aware of the following restrictions:
Caution
While VLAN Trunking Protocol (VTP) Version 2 must be enabled on a Catalyst 5000 for Token Ring to
function, do not use VTP to distribute VLAN configuration information between the switches. Configure
the switches to operate in VTP transparent mode and manually configure the VLANs on each switch.
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While you can have only one LEC for each TrBRF in each module, you can have more than one module
installed. These additional modules allow you to have more than one LEC per TrBRF, which means the
module can participate in more than one ELAN. The ELANs, however, cannot be parallel or the Spanning-
Tree Protocol will block one of the connections.
Note
Configuring more than one LEC for a TrBRF on a single ATM module will adversely affect frame
forwarding.
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Two-port and multiport SRB between ELANs and between ELANs and a Token Ring LAN
SRB, source-route transparent bridging (SRT), and source-route switching
If you plan to run both Ethernet and Token Ring LANE, the Ethernet LANE software and the Token
Ring LANE software must be run on separate ATM modules.
All ATM switches have identical lists of the global LECS addresses with the identical priorities.
Ensure that the spanning-tree port cost and priority for the ATM port are configured so that the ATM
port is the preferred path (the lowest port cost with the highest priority).
Only one LEC can be defined for each subinterface. Up to 256 subinterfaces per ATM module can be
configured.
Do not create more than one LEC for each Token Ring Bridge Relay Function (TrBRF) in each ATM
module.
Do not configure parallel ELANs within a TrBRF (parallel ELANs are those ELANs that form a loop
between switches).
Do not create more than one LEC for each Token Ring Concentrator Relay Function (TrCRF) per
ATM module.
Ensure that all-routes explorer (ARE) reduction is enabled (using the set tokenring reduction enable
command) on the Token Ring module.
The number of LESs that can be defined per ELAN is unlimited; however, only one LES per ELAN
can be active at a time.
When a LECS switchover occurs, no previously joined clients are affected.
In a LES/BUS switchover, there is a momentary loss of clients until all clients are transferred to the
new LES/BUS.
LECSs automatically come up as masters until a higher-level LECS takes priority.
Using FSSRP, you can configure redundant LESs or BUSs and LECSs to reduce the possibility of a
server failure resulting in loss of communication on the LANE network. With redundant LES/BUSs
LANE Token Ring Components