Administrator Guide

Version Description
9.2(1.0) Introduced on the Z9500.
9.0.2.0 Introduced on the S6000.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.7.0 Introduced on the S4810.
8.1.1.0 Introduced on the E-Series.
6.5.1.9 and 7.4.1.0 Introduced on the E-Series.
7.8.1.0 Introduced on the C-Series and S-Series with the thresholds option.
Usage Information
The globally assigned 48-bit multicast address 01-80-C2-00-00-01 is used to send and receive pause frames. To
allow full-duplex flow control, stations implementing the pause operation instruct the MAC to enable the reception
of frames with a destination address equal to this multicast address.
When a port receives traffic at a higher rate than it can process, the frames are stored in the port buffer. As a
result, buffer usage increases. When the buffer usage reaches the value specified in the “pause-threshold”
argument, the port sends PAUSE frame to the connected link partner to stop sending the traffic. Eventually this
reduces the buffer usage. When the buffer usage drops by the value specified in the “resume-threshold”, the port
again sends a PAUSE frame with 0 as wait-time. This results in resume of the paused traffic flow.
Important Points to Remember
• Do not enable tx pause when buffer carving is enabled. For information and assistance, consult Dell EMC
Networking TAC.
• The only configuration applicable to half duplex ports is rx off tx off. The following error is returned:
Can’t configure flowcontrol when half duplex is configure, config ignored
• Half duplex cannot be configured when the flow control configuration is on (default is rx on tx on). The
following error is returned:
Can’t configure half duplex when flowcontrol is on, config ignored
NOTE: The flow control must be off (rx off tx off) before configuring the half duplex.
• Speeds less than one Gig cannot be configured when the asymmetric flow control configuration is on. The
following error is returned:
Can’t configure speed <1G when Asymmetric flowcontrol is on, config ignored
• Dell EMC Networking OS only supports rx on tx on and rx off tx off for speeds less than one Gig
(Symmetric).
NOTE:
If you use the disable rx flow control command, Dell EMC Networking recommends
rebooting the system.
NOTE: Dell EMC Networking OS does not support mirroring of tx pause frames.
Example
DellEMC(conf-if-Te-1/1)# show config
!
interface TenGigabitEthernet 1/1
no ip address
switchport
no negotiation auto
flowcontrol rx off tx on
no shutdown
...
Example (Monitor
Session)
DellEMC(conf-if-te-1/5)#show config
!
interface TenGigabitEthernet 1/5
no ip address
672 Interfaces