System information

10-28
Port Status and Basic Configuration
QoS Passthrough Mode
Note As stated earlier, use of this QoS-Passthrough-Mode feature generally assumes
that QoS tagged frames are not being sent through the switch. The receipt of
priority 6 or 7 packets may in fact suffer packet drops depending on the traffic
load of non-priority 6 or 7 packets.
Priority Mapping With and Without QoS Passthrough Mode
The switch supports 802.1p VLAN tagging, which is used in conjunction with
the outbound port priority queues to prioritize outbound traffic.
An 802.1Q VLAN tagged packet carries an 802.1p priority setting (0-7). If the
switch receives a tagged packet, it is placed into the appropriate queue based
on the frame's 802.1p priority setting. The mapping with/without QoS
Passthrough Mode is as follows:
How to Enable or Disable QoS Passthrough Mode
QoS Pass-Through Mode is set to “optimized” by default.
802.1p Priority
Setting
Prioritization Queue Placement
Default QoS
Setting
QoS Passthrough
Mode
1 1 (low) 2 (normal)
2 1 (low) 2 (normal)
0 or
Unspecified
2 (normal) 2 (normal)
3 2 (normal) 2 (normal)
4 3 (medium) 2 (normal)
5 3 (medium) 2 (normal)
6 4 (high) 4 (high)
7 4 (high) 4 (high)
Syntax: [no] qos-passthrough-mode [optimized | typical]
write memory
reload
The above command sequence sets QoS pass-through mode to
‘optimized’. The no form of the command sequence sets QoS
pass-through mode to ‘typical’. Default: Optimized