Administrator Guide

Layer 2 Overhead Difference Between Link MTU and IP MTU
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.
• Members can have different Link MTU values. Tagged members must have a link MTU 4–bytes higher than untagged members to
account for the packet tag.
• The VLAN link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values configured on the VLAN members.
For example, the VLAN contains tagged members with Link MTU of 1522 and IP MTU of 1500 and untagged members with Link MTU of
1518 and IP MTU of 1500. The VLAN’s Link MTU cannot be higher than 1518 bytes and its IP MTU cannot be higher than 1500 bytes.
NOTE: When configuring IP MTU on an interface, make sure to set the same or maximum IP MTU value on both ingress
and egress interfaces to make IPv4 traffic flow.
Port-Pipes
A port pipe is a Dell EMC Networking-specific term for the hardware packet-processing elements that handle network traffic to and from
a set of front-end I/O ports. The physical, front-end I/O ports are referred to as a port-set. In the command-line interface, a port pipe
is entered as port-set port-pipe-number.
Auto-Negotiation on Ethernet Interfaces
By default, auto-negotiation of speed and full duplex mode is enabled on 100/1000 Base-T Ethernet interfaces. Only 10GE interfaces do
not support auto-negotiation.
When using 10GE interfaces, verify that the settings on the connecting devices are set to no auto-negotiation.
The local interface and the directly connected remote interface must have the same setting, and auto-negotiation is the easiest way to
accomplish that, as long as the remote interface is capable of auto-negotiation.
NOTE:
As a best practice, Dell EMC Networking recommends keeping auto-negotiation enabled. Only disable auto-
negotiation on switch ports that attach to devices not capable of supporting negotiation or where connectivity issues
arise from interoperability issues.
NOTE: If the interface does not come up when you configure 10/100/1000G speed, configure the interface speed using
the speed command manually on both the ends and disable autonegotiation if it is enabled.
Setting the speed to 10/100/1000 Mbps on SFP-1G-T
transceiver
Dell EMC Networking OS allows you to disable the auto-negotiation on the SFP-1G-T transceiver connected interface and set the speed
manually to 10/100/1000 Mbps. You can disable the auto-negotiation using no negotiation auto command and enable setting the
interface speed using the speed command at the INTERFACE mode.
Interfaces
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