The DSCP Policy Table associates an 802.1p priority with a DSCP codepoint in an IPv4/IPv6 packet. Using DSCP codepoints in your network allows you to set a LAN policy that operates independently of 802.1Q VLAN-tagging.
In the default state, most of the 64 codepoints do not assign an 802.1p priority, as indicated by No-override
in The default DSCP Policy Table. However, some codepoints, such as Assured Forwarding and Expedited Forwarding, have a default 802.1p priority setting.
Use the following commands to display the DSCP Policy table, configure the codepoint-priority assignments, and assign optional names to the codepoints.
Syntax:
Removes the currently configured 802.1p priority that is associated with the specified
and displays the
<codepoint>
No-override
setting. The codepoint policy name, if configured, is also removed.
The default DSCP Policy Table
DSCP policy | 802.1p priority | DSCP policy | 802.1p priority | DSCP policy | 802.1p priority |
---|---|---|---|---|---|
000000 | No-override | 010110 | 3* | 101011 | No-override |
000001 | No-override | 010111 | No-override | 101100 | No-override |
000010 | No-override | 011000 | No-override | 101101 | No-override |
000011 | No-override | 011001 | No-override | 101110 | 7** |
000100 | No-override | 011010 | 4* | 101111 | No-override |
000101 | No-override | 011011 | No-override | 110000 | No-override |
000110 | No-override | 011100 | 4* | 110001 | No-override |
000111 | No-override | 011101 | No-override | 110010 | No-override |
001000 | No-override | 011110 | 5* | 110011 | No-override |
001001 | No-override | 011111 | No-override | 110100 | No-override |
001010 | 1* | 100000 | No-override | 110101 | No-override |
001011 | No-override | 100001 | No-override | 110110 | No-override |
001100 | 1* | 100010 | 6* | 110111 | No-override |
001101 | No-override | 100011 | No-override | 111000 | No-override |
001110 | 2* | 100100 | 6* | 111001 | No-override |
001111 | No-override | 100101 | No-override | 111010 | No-override |
010000 | No-override | 100110 | 7* | 111011 | No-override |
010001 | No-override | 100111 | No-override | 111100 | No-override |
010010 | 0* | 101000 | No-override | 111101 | No-override |
010011 | No-override | 101001 | No-override | 111110 | No-override |
010100 | 0* | 101010 | No-override | 111111 | No-override |
010101 | No-override | ||||
*Assured Forwarding codepoints; configured by default on the switches covered in this guide. **Expedited Forwarding codepoint configured by default. |
In a few cases, such as 001010 and 001100, a default DSCP policy (implied by the DSCP standards for Assured-Forwarding and Expedited-Forwarding) is used. You can change the priorities for the default policies by using the qos dscp-map
command.<codepoint>
priority <0-7>
The currently configured DSCP policies (codepoint and associated 802.1p priority) are not enabled until you configure a global or classifier-based QoS policy to mark matching packets or configure a global IP-Diffserv classifier.
The default DSCP Policy Table lists the switch’s default codepoint/priority settings. If you change the priority of any codepoint setting to a non-default value and then execute write memory
, the switch will list the non-default setting in the show config
display. For example, in the default configuration, the following codepoint settings are true:
If you change all three settings to a priority of 3, and then execute write memory
, the switch will reflect these changes in the show config
listing:
Effect of No-override
: If you configure a global IP-Diffserv classifier and No-override
is displayed for the 802.1p priority associated with a codepoint, DSCP marking cannot be performed on matching outbound packets. However, QoS does not affect the packet-queuing 802.1p priority or VLAN tagging carried in the packet.
In this case, the packets are handled as follows (as long as no other QoS feature creates priority assignments for them):
If you try to modify the priority associated with a DSCP codepoint in a DSCP policy using the qos dscp-map priority
command, and if the DSCP policy is currently used by one or more global QoS or classifier-based QoS policies, the following error message is displayed:
In this case, you can enter the following QoS show
commands to identify in which global and classifier-based QoS configurations the DSCP policy is currently used:
After determining the QoS configurations in which the DSCP-priority mapping is used, you can either delete a QoS configuration and reset the DSCP-priority mapping to No-override
, or change either the 802.1p priority or the codepoint used in the QoS configuration.
Example:
If codepoint 000001 is currently mapped to priority 6, and several global QoS policies use this codepoint to assign a priority to their respective types of matching traffic, you can change the priority associated with the codepoint as follows:
-
Identify the global and classifier-based QoS policies that use the codepoint.
-
-
Reconfigure each QoS policy by re-entering a different DSCP codepoint or a different 802.1p priority associated with the codepoint.
-
Enter the
no qos
or<classifier>
no policy
command to remove the current DSCP policy with codepoint 000001 and reset the priority to<qos-policy>
No-override
.
-
-
Use the
qos dscp-map 000001 priority <0-7>
command to remap DSCP 000001 to the desired priority. -
-
Reconfigure codepoint 000001 in the QoS policies in which you want to use the new DSCP-priority mapping to mark matching packets.
-
Leave a QoS policy in which you use DSCP 000001 to mark matching packets with the associated
No-override
priority mapping.
-
See the error messages below to troubleshoot an error condition that results from reconfiguring a DSCP policy:
Error message | Description |
---|---|
DSCP Policy < decimal-codepoint > not configured | You have tried to configure a codepoint in a global or classifier-based QoS policy for which there is no associated priority (No-override ). Use the qos dscp-map command to configure a priority for the codepoint, then re-enter the codepoint in the QoS configuration. |
Cannot modify DSCP Policy < codepoint > - in use by other qos rules. | You have tried to configure a codepoint in a global or classifier-based QoS policy that is already in use by other QoS policies. Before remapping the codepoint to a new priority, you must first reconfigure the other QoS policies so that they do not use the current codepoint-priority mapping. You can have multiple QoS policies that use the same codepoint to mark packets as long as it is acceptable for all such policies to use the same 802.1p priority. |
In this example, the codepoint 000001 is in use by one or more global QoS policies. If you try to modify the priority currently associated with the codepoint, an error message similar to the following is displayed:
Error message for changing the priority on a DSCP policy
HP Switch(config)# qos dscp-map 1 priority 2 Cannot modify DSCP Policy 1 - in use by other qos rules.
In this case, you would use steps similar to the following to change the priority.
-
Identify the global and classifier-based QoS policies that use the codepoint whose DSCP-priority mapping you want to change.
Identifying the QoS policies that use a codepoint
HP Switch(config)# show qos device-priority Device priorities Device Address Apply Rule | DSCP Priority -------------- ---------- - ---- ----------- 10.26.50.104 DSCP | 1 6 HP Switch(config)# show qos port-priority Port priorities Port Apply rule | DSCP Priority Radius Override ---- ---------- ----- ---------- --------------- 1 No-override | No-override No-override 2 No-override | No-override No-override 3 DSCP | 1 6 No-override 4 No-override | No-override No-override . . . HP Switch(config)# show qos tcp-udp-port-priority TCP/UDP port based priorities | IP Packet Application Protocol | Type Port Apply rule | DSCP Priority -------- + ---------- ---------- ---------- + ------ -------- UDP | IPv4 1260 DSCP | 1 6
-
Change each QoS configuration by assigning a different DSCP policy or a different 802.1p priority, or by removing the currently configured DSCP policy and restore the default No-override setting; for example:
-
Delete the current DSCP policy used to mark matching packets for a global IP-device policy (
no qos device-priority
command) and reset the default priority mapping toNo-override
. -
Create a new DSCP policy to use when you reconfigure QoS policies to use the new codepoint-priority mapping.
-
Configure a global QoS source-port policy to mark matching packets with the new DSCP policy.
-
Assign the global QoS policy that matches
udp-port 1260
packets to a different 802.1p priority.a) HP Switch(config)# no qos device-priority 10.26.50.104 b) HP Switch(config)# qos dscp-map 000100 priority 6 c) HP Switch(config)# int 3 qos dscp 000100 d) HP Switch(config)# qos udp-port 1260 priority 2
-
-
Reconfigure the desired priority for the 000001 codepoint.
HP Switch(config)# qos dscp-map 000001 priority 4
-
Reconfigure QoS policies with the original codepoint (000001) to mark packets with the new DSCP-priority mapping, or leave QoS policies as currently configured from Step 2.