Specifications

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Figure 19. WRED high and low thresholds

WRED also supports high and low threshold settings for a given threshold. In the diagram above, you can see there

are two thresholds (1 and 2). Threshold #1 is a level under which no traffic mapped to that threshold is dropped.

When that threshold is exceeded, traffic mapped to that threshold (CoS 0 and 1) is eligible to be dropped. The more

the threshold is exceeded, the greater rate at which those packets are dropped. When Threshold 2 is exceeded,

traffic marked with CoS 2 and 3 will start to be dropped, but at a rate less than traffic marked CoS 0 and 1.

How do you know if your line card supports WRED? Simply run the following command and in the output is a section

indicating support or no support for WRED on that port. The first example below shows a port that does not support

WRED. This is a show output of a 10/100 port on the WS-X6148-RJ45:

Cat6500# show queueing int f4/1

<snip>

queue tail-drop-thresholds

--------------------------

1 80[1] 100[2]

2 80[1] 100[2] <snip>

Note that in the output above it refers to the Tail Drop thresholds. The next example below shows a port that does

support WRED. This is the same CLI output from a 10/100/1000 port on a WS-X6516-GETX:

Cat6500# show queueing int f4/1

<snip>

queue random-detect-min-thresholds

----------------------------------

1 40[1] 70[2]

2 40[1] 70[2]

queue random-detect-max-thresholds

----------------------------------

1 70[1] 100[2]