Deployment Guide

Table Of Contents
Table 43. 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.
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.
CR4 Auto-Negotiation
You can configure interface type as CR4 with auto-negotiation enabled. Many DAC cable link issues are resolved by setting the
interface type as CR4. If the CR4 optic fails to come up, use the autoneg option.
To configure interface type as CR4 with auto-negotiation enabled, use the following commands.
Set the interface type as CR4 with auto-negotiation enabled.
INTERFACE mode
intf-type cr4 autoneg
To disable CR4 auto-negotiation, use the no intf-type cr4 autoneg command.
Verify the configuration.
INTERFACE mode
show config
DellEMC(conf)#interface hundredGigE 1/1/1
DellEMC(conf-if-hu-1/1/1)#intf-type cr4 autoneg
DellEMC(conf-if-hu-1/1/1)#no intf-type cr4 autoneg
DellEMC(conf-if-hu-1/1/1)#show config
!
interface hundredGigE 1/1/1
402
Interfaces