Reference Guide

446 | Interfaces
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Ethernet Pause Frames flow control must be enabled on all ports on a chassis or a line card. If not, the
system may exhibit unpredictable behavior.
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
.
Configure MTU Size on an Interface
If a packet includes a Layer 2 header, the difference in bytes between the link MTU and IP MTU must be
enough to include the Layer 2 header. For example, for VLAN packets, if the IP MTU is 1400, the Link
MTU must be no less than 1422:
1400-byte IP MTU + 22-byte VLAN Tag = 1422-byte link MTU
The MTU range is 592-12000, with a default of 1500. On the E-Series, the user must enter the ip mtu
command to manually configure the IP MTU to compensate for the Layer 2 header. The C-Series and
S-Series automatically configure the IP MTU.
Note: If rx flow control is disabled, Dell Force10 recommends rebooting the system.
Command Syntax Command Mode Purpose
flowcontrol rx [off | on] tx [off | on] [threshold
{<1-2047> <1-2013> <1-2013>}]
INTERFACE Control how the system responds to and
generates 802.3x pause frames on 1 and 10Gig
line cards.
Defaults:
C-Series: rx off tx off
E-Series: rx on tx on
S-Series: rx off tx off
S4810: rx off
Parameters:
rx on: Enter the keywords rx on to process the received flow control frames
on this port.
rx off
: Enter the keywords rx off to ignore the received flow control frames on
this port.
tx on
: Enter the keywords tx on to send control frames from this port to the
connected device when a higher rate of traffic is received.
tx off
: Enter the keywords tx off so that flow control frames are not sent from
this port to the connected device when a higher rate of traffic is received.
threshold (C-Series and S-Series only): When tx on is configured, the
user can set the threshold values for:
Number of flow-control packet pointers: 1-2047 (default = 75)
Flow-control buffer threshold in KB: 1-2013 (default = 49KB)
Flow-control discard threshold in KB: 1-2013 (default= 75KB)
Pause control is triggered when either the flow control buffer threshold
or flow control packet pointer threshold is reached.