Users Guide

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.
• 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.
Port-Pipes
A port pipe is a Dell 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 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.
410 Interfaces