Enhancements in Release F.04.08

Configuring Port-Based Priority for Incoming Packets

Operating Rules for Port-Based Priority on Series 2500 Switches

In the switch’s default configuration, port-based priority is configured as "0" (zero) for inbound traffic on all ports.

On a given port, when port-based priority is configured as "0" (zero) or 1 - 7, an inbound, untagged packet adopts the specified priority and is sent to the corresponding outbound queue on the outbound port. (See table 8, “Mapping Priority Settings to Device Queues”, on page 133.) If the outbound port is a tagged member of the applicable VLAN, then the packet carries a tag with that priority setting to the next downstream device.

On a given port, an inbound, tagged packet received on the port keeps the priority specified in the tag and is assigned an outbound queue on the basis of that priority (regardless of the port-based priority configured on the port) . (Refer to table 8, “Mapping Priority Settings to Device Queues” on page 133.)

If a packet leaves the switch through an outbound port configured as an untagged member of the packet’s VLAN, then the packet leaves the switch without a VLAN tag and thus without an 802.1p priority setting.

Trunked ports do not allow non-default (1 - 7) port-based priority settings. If you configure a non-default port-based priority value on a port and then add the port to a port trunk, then the port-based priority for that port is returned to the default "0".

Configuring and Viewing Port-Based Priority

This command enables or disables port-based priority on a per-port basis. You can either enter the command on the interface context level or include the interface in the command.

Syntax: qos priority < 1 - 7 >

Configures a non-default port-based 802.1p priority for

 

incoming, untagged packets on the designated ports, as

 

described under "Operating Rules for Port-Based Priority",

 

above.

qos priority 0

Returns a port-based priority setting to the default "0" for

 

untagged packets received on the designated port(s).

 

In this state the switch handles the untagged packets with

 

"Normal" priority. (Refer to Table 8 on page 133.)

show running-config

Lists any non-default (1 - 7) port-based priority settings in

 

the running-config file on a per-port basis.

show config

Lists any non-default (1 - 7) port-based priority settings in

 

the startup-config file on a per-port basis. If the priority is

 

set to the (default) "0", the setting is not included in the

 

show config listing.

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