Install Guide

Enabling Pause Frames
Enable Ethernet pause frames flow control on all ports on a chassis or a line card. If not, the system may exhibit unpredictable
behavior.
NOTE: Changes in the flow-control values may not be reflected automatically in the show interface output. As a
workaround, apply the new settings, execute shut then no shut on the interface, and then check the running-config of
the port.
NOTE: If you disable rx flow control, Dell EMC Networking recommends rebooting the system.
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 the Ethernet ports.
INTERFACE mode
flowcontrol {rx [off | on] tx [off | on] | 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.
○ 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 EMC 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 EMC Networking OS and the number of bytes.
Table 42. 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.
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Interfaces