Port Status and Basic Configuration

Configuring Port-Based Priority for Incoming Packets on the 4100gl and 6108 Switches

For example, suppose you have configured port A10 to assign a priority level of 1 (low):

■An untagged packet coming into the switch on port A10 and leaving the switch through any other port configured as a tagged VLAN member would leave the switch as a tagged packet with a priority level of 1.

■A tagged packet with an 802.1p priority setting of 0 (zero) coming into the switch on port A10 and leaving the switch through any other port config­ ured as a tagged VLAN member would leave the switch as a tagged packet with a priority level of 1.

■A tagged packet with an 802.1p priority setting (1 - 7) coming into the switch on port A10 and leaving the switch through any other port config­ ured as a tagged VLAN member would keep its original priority setting (regardless of the port-based priority setting on port A10).

N o t e

For a packet to carry a given 802.1p priority level from end-to-end in a network,

 

the VLAN for the packet must be configured as tagged on all switch-to-switch

 

links. Otherwise the tag is removed and the 802.1p priority is lost as the packet

 

moves from one switch to the next.

 

 

Operating Rules for Port-Based Priority

These rules apply to the operation of port-based priority on the switch.

■ 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 - 7, an inbound, untagged packet adopts the specified priority and is sent to the corresponding outbound queue on the outbound port. (See table 10-3, “Mapping Priority Settings to Device Queues”, on page 10-30.) 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, when port-based priority is configured as 0 - 7, an inbound, tagged packet with a priority of 0 (zero) adopts the specified priority and is sent to the corresponding outbound queue on the outbound port. (See table 10-3, “Mapping Priority Settings to Device Queues”, on page 10-30.) 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.

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