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The following table lists the various Layer 2 overheads found in the Dell EMC Networking OS and the number of bytes.
Table 39. 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 channels 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 4bytes 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 VLANs 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 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 10/100/1000 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:
Setting the Speed of Ethernet Interfaces
To discover whether the remote and local interface requires manual speed synchronization, and to manually synchronize them if
necessary, use the following command sequence.
1. Determine the local interface status. Refer to the following example.
Interfaces
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