Reference Guide

570 | Interfaces
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• Ends when both the packet pointer and the buffer threshold fall below 50% of the threshold
settings.
The discard threshold defines when the interface starts dropping the packet on the interface. This may
be necessary when a connected device does not honor the flow control frame sent by the S-Series. The
discard threshold should be larger than the buffer threshold so that the buffer holds at least hold at least
3 packets.
On 4-port 10G line cards: Changes in the flow-control values are not reflected automatically in the
show interface output for 10G interfaces. This issue results from the fact that 10G interfaces do not
support auto-negotiation per-se. On 1G interfaces, changing the flow control values causes an
automatic interface flap, after which PAUSE values are exchanged as part of the auto-negotiation
process. As a workaround, apply the new settings, execute shut followed by no shut on the interface,
and then check the running-config of the port.
Important Points to Remember
• Do not enable tx pause when buffer carving is enabled. Consult Dell Force10 TAC for
information and assistance.
• Asymmetric flow control (rx on tx off or rx off tx on) setting for the interface port less than 100
Mb/s speed is not permitted. The following error is returned:
Can’t configure Asymmetric flowcontrol when speed <1G, config
ignored
• 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
• Speeds less than 1 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
• FTOS only supports rx on tx on and rx off tx off for speeds less than 1 Gig (Symmetric).
• On the C-Series and S-Series systems, the flow-control sender and receiver must be on the same
port-pipe. Flow control is not supported across different port-pipes on the C-Series or S-Series
system.
Example
Figure 23-4. show running config (partial)
Note: The flow control must be off (rx off tx off) before configuring the half duplex.
FTOS(conf-if-gi-0/1)#show config
!
interface GigabitEthernet 0/1
no ip address
switchport
no negotiation auto
flowcontrol rx off tx on
no shutdown
...