Lenovo Flex System Fabric CN4093, Application Manual

Page: 304 / 634

304
CN4093 Application Guide for N/OS 8.4
It is recommended that a configuration backup be made prior to turning CEE on or
off. Viewing the configuration file will allow the administrator to manually
re ‐ create the equivalent configuration under the new CEE mode, and will also allow
for the recovery of the prior configuration if necessary.
Effects on Flow Control
When CEE is off (the default), 802.3x standard flow control is enabled on all switch
ports by default.
When CEE is turned on, standard flow control is disabled on all ports, and in its
place, PFC (see “Priority ‐ Based Flow Control” on page 312 ) is enabled on all ports
for 802.1p priority value 3. This default is chosen because priority value 3 is
commonly used to identify FCoE traffic in a CEE environment and must be
guaranteed lossless behavior. PFC is disabled for all other priority values.
It is recommend that a configuration backup be made prior to turning CEE on or off.
Viewing the configuration file will allow the administrator to manually re ‐ create the
equivalent configuration under the new CEE mode, and will also allow for the
recovery of the prior configuration if necessary.
When CEE is on, PFC can be enabled only on priority value 3 and one other
priority. If flow control is required on additional priorities on any given port,
consider using standard flow control on that port, so that regardless of which
priority traffic becomes congested, a flow control frame is generated.