Dell PowerConnect 8024, User Configuration Manual

Page: 816 / 1294

816
Configuring Data Center Bridging Features
PFC Configuration Example
The network in this example handles both data and voice traffic. Because the
voice traffic is time sensitive, it requires a higher priority than standard data
traffic. The voice traffic uses VLAN 100 and has an 802.1p priority of 5, which
is mapped to hardware queue 4. IP phones are connected to ports 3, 5, and 10,
so PFC is enabled on these ports with 802.1p priority 5 traffic as no-drop. The
configuration also enables VLAN tagging so that the 802.1p priority is
identified. This example assumes the voice VLAN (VLAN 100) has already
been configured. The administrator may need to perform other configuration
steps to ensure suitable network operation, including configuring the
bandwidth allocation for the drop and no-drop priorities or to enable or
disable the DCBX protocol.
1
Map 802.1p priority 5 to traffic class 4. The following command changes
the priority to traffic class mapping to be one-to-one, based upon the
default switch settings. For lossless service, a priority must be mapped one-
to-one to a traffic class. For more information about traffic classes, see
"Configuring Class-of-Service" on page 1143. For a complete example of
manually configuring a PC81xx switch for iSCSI with PFC, refer to "iSCSI
Optimization Configuration Examples" on page 409.
console# configure
console(config)# classofservice dot1p-mapping 5 4
2
Enter Interface Configuration mode for ports 3, 5, and 10, and then enter
Data Center Bridging mode for these ports.
console(config)# interface range te1/0/3, te1/0/5,
te1/0/10
console(config-if)#
datacenter-bridging
3 Enable PFC and configure traffic marked with 802.1p priority 5 to be
paused rather than dropped when congestion occurs.
console(config-dcb)# priority-flow-control mode on
console(config-dcb)#
priority-flow-control
priority 5 no-drop
CAUTION: All ports may be briefly shutdown when modifying either flow
control (FC) or PFC settings. PFC uses a control packet defined in
802.1Qbb and is not compatible with IEEE 802.3 Annex 31B flow
control.