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Enhancements
Releases M.08.90 and M.08.91 Enhancements
The “legacy-path-cost” CLI command does not affect or replace functionality of the “spanning-
tree force-version” command. The “spanning-tree force-version” controls whether MSTP will
send and process 802.1w RSTP, or 802.1D STP BPDUs. Regardless of what the “legacy-path-cost”
parameter is set to, MSTP will interoperate with legacy STP bridges (send/receive Config and
TCN BPDUs).
spanning-tree legacy-mode - A “macro” that is the equivalent of executing the “spanning-tree legacy-
path-cost” and “spanning-tree force-version stp-compatible” commands.
no spanning-tree legacy-mode - A “macro” that is the equivalent of executing the “no spanning-tree
legacy-path-cost” and “spanning-tree force-version mstp-compatible” commands.
When either legacy-mode or legacy-path-cost control is toggled, all default path costs will be
recalculated to correspond to the new setting, and spanning tree is recalculated if needed.
QoS Pass-Through Mode
Release M.08.91 introduced a new command that allows the configuration of the Quality of Service
(QoS) queues to be selected. By better matching the configuration of the QoS queues to the amount
of prioritized and non-prioritized traffic being transferred, performance can be improved and packet
loss due to over-subscription can be minimized.
In previous software versions, the 3400cl and the 6400cl switches had four QoS queues of equal size.
Depending on the mix of prioritized and non-prioritized traffic, this configuration might not always
optimize performance and could result in dropped packets when resources were over-subscribed.
Starting with this software version, four QoS Pass-Through modes are available for use. The number
of queues and the size of the memory buffer used by each queue differs in each mode. Table 2 below
summarizes the QoS queue configuration of each mode
Table 2. QoS Pass-Through Modes
QoS Pass-Through Mode Number of
Queues
QoS Queue Memory Buffer
Configuration
Description
typical (default) 4 One large queue for Priority 0
and 3 traffic and three other
queues for the remaining traffic.
A mix of prioritized and non-
prioritized traffic. This is the
default mode, used when QoS
Pass-Through is disabled.
balanced 4 All queues are the same size. Equal amounts of prioritized and
non-prioritized traffic. This is the
same mode used in pre-M.08.78
software versions.
one-queue 1 One large queue.
1
No traffic is prioritized.
optimized 2 One small queue for Priority 6
and 7 traffic; one large queue for
all other traffic.
Most traffic is not prioritized.
1
This mode has a small queue used exclusively for Priority 7 management and control traffic.
