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Configuring the MLS Engine

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cache on the NFFC or PFC. This attribute can be modified and adjusted. The
following sections describe how this can be done.

Modifying the Cache Aging Time

A layer 3 cache entry will remain in cache for 256 seconds after the last
packet for the flow has passed through the switch. This is the default value.
The value can be changed to different values depending on your needs as a
network administrator.

The syntax is set mls agingtime agingtime, where agingtime is a

value of seconds. The value is a multiple of 8. The valid range is from 8 to
2032. If the value specified is not a multiple of 8, the nearest multiple will be
used. Here is an example:

Switch2> (enable) set mls agingtime 125

Multilayer switching aging time set to 128

Switch2> (enable)

Modifying Fast Aging Time

When the layer 3 cache grows greater than 32K in size, there is an increased
possibility that the PFC or NFFC will not be able to perform all layer 3
switching, causing some packets to be forwarded to the router. To aid in
maintaining a layer 3 cache smaller than 32K, you can enable and adjust fast
aging times

Because some flows can be very short, you can enable packet thresholds

that can be used in correlation with the fast aging time to quickly age out
these entries. Both of these attributes are thresholds. When you set the fast
aging time, you specify the amount of time for which n number of packets
(defined by the packet threshold) must have used the cache entry.

When a flow is initialized, the switch must see a number of packets equal

to or greater than the packet threshold set within the time specified by the
fast aging time. If this criterion isn't met, the cache entry is aged out
immediately.

Valid values for the fast aging time are 32, 64, 96, and 128. Valid values

for the packet threshold are 0, 1, 3, 7, 15, 31, and 63. Let's do an example
so we can understand how this works.

Say you configured a fast aging time of 64 seconds and the packet thresh-

old to 31 packets using the set mls agingtime fast 64 31 command on

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