Users Guide

The flow control sender and receiver must be on the same port-pipe. Flow control is not supported
across different port-pipes.
To enable pause frames, use the following command.
• Control how the system responds to and generates 802.3x pause frames on 10 Gigabit line cards.
INTERFACE mode
flowcontrol rx [off | on] tx [off | on] [threshold {<1-2047> <1-2013>
<1-2013>}]
– 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: when you configure tx on, you can set the threshold values for:
* Number of flow-control packet pointers: the range is from 1 to 2047 (default = 75).
* Flow-control buffer threshold in KB: the range is from 1 to 2013 (default = 49KB).
* Flow-control discard threshold in KB: the range is from 1 to 2013 (default= 75KB)
Pause control is triggered when either the flow control buffer threshold or flow control packet pointer
threshold is reached.
Configure the 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 from 594 to 12000, with a default of 1554 IP MTU automatically configures.
The following table lists the various Layer 2 overheads in the Dell Networking OS and the number of
bytes.
Table 37. Layer 2 Overhead
Layer 2 Overhead Difference Between Link MTU and IP MTU
Ethernet (untagged) 18 bytes
VLAN Tag 22 bytes
Untagged Packet with VLAN-Stack Header 22 bytes
Tagged Packet with VLAN-Stack Header 26 bytes
Link MTU and IP MTU considerations for port channels and VLANs are as follows.
Port Channels:
Interfaces
501