Administrator Guide

To enable pause frames, use the following command.
• Control how the system responds to and generates 802.3x pause frames on the Ethernet ports.
INTERFACE mode
flowcontrol {rx [off | on] tx [off | on] [negotiate] | monitor session-ID}
• 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.
• negotiate: enable pause-negotiation with the egress port of the peer device. If the negotiate command is not used, pause-
negotiation is disabled. 40 gigabit Ethernet interfaces do not support pause-negotiation.
• monitor session-ID: Enter the keyword monitor then the session–ID to enable mirror flow control frames on the port. The
session–ID range is from 1 to 65535.
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 following table lists the various Layer 2 overheads found in Dell Networking OS and the number of bytes.
The MTU range is from 592 to 9216, with a default of 9216. IP MTU automatically configures.
The following table lists the various Layer 2 overheads found in the Dell Networking OS and the number of bytes.
Table 41. 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:
• All members must have the same link MTU value and the same IP MTU value.
• The port channel link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values configured on the channel
members.
For example, if the members have a link MTU of 2100 and an IP MTU 2000, the port channel’s MTU values cannot be higher than 2100 for
link MTU or 2000 bytes for IP MTU.
VLANs:
• All members of a VLAN must have the same IP MTU value.
Interfaces
421