Quality of Service (QoS): Managing Bandwidth More Effectively
Using QoS Classifiers To Configure Quality of Service for Outbound Traffic
3400cl/6400cl Switch Restriction. On the 3400cl/6400cl switches, “mix-
ing” ToS DSCP policies and 802.1p priorities is not recommended. Refer to the
Note on page
8-10.
For more on DSCP, refer to “Terminology” on page 8-5.
Steps for Creating a Policy Based on IP Address. This procedure cre-
ates a DSCP policy for IPv4 packets carrying the selected IP address (source
or destination).
1. Identify the IP address to use as a classifier for assigning a DSCP policy.
2. Determine the DSCP policy for packets carrying the selected IP address:
a. Determine the DSCP you want to assign to the selected packets. (This
codepoint will be used to overwrite the DSCP carried in packets
received from upstream devices.)
b. Determine the 802.1p priority you want to assign to the DSCP.
3. Configure the DSCP policy by using dscp-map to configure the priority to
the codepoint you selected in step 2
a. (For details, refer to “Differentiated
Services Codepoint (DSCP) Mapping” on page 8-62.)
Note s A codepoint must have an 802.1p priority assignment (0 - 7) before you can
configure a policy for prioritizing packets by IP address. If a codepoint you
want to use shows No-override in the Priority column of the DSCP map (show
qos dscp-map), then you must assign a 0 - 7 priority before proceeding.
On 5300xl switches, DSCP policies cannot be applied to IPv4 packets having
IP options. For more information on packet criteria and restrictions, refer to
8-15 on page 8-70.
4. Configure the switch to assign the DSCP policy to packets with the
specified IP address.
Syntax: qos dscp-map < codepoint > priority < 0 - 7 >
This command is optional if a priority is already assigned
to the < codepoint >. The command creates a DSCP policy by
assigning an 802.1p priority to a specific DSCP. When the
switch applies this policy to a packet, the priority determines
the packet’s queue in the outbound port to which it is sent. If
the packet leaves the switch on a tagged port, it carries the
802.1p priority with it to the next downstream device. If the
packet is IPv4, the packet’s DSCP will be replaced by the
codepoint specified in this command. (Default: For most
codepoints,
No-override. See figure 8-14 on page 8-63.)
8-33
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