Users Guide

Version Description
7.5.1.0 Introduced on the C-Series.
pre-Version 6.2.1.0 Introduced on the E-Series.
Usage Information
If the packet includes a Layer 2 header, the dierence between the link MTU and IP MTU (ip mtu
command) must be enough bytes to include the Layer 2 header.
When you enter the no mtu command, Dell Networking OS reduces the IP MTU value to 1536 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
congured 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 same IP MTU value.
• Members can have dierent 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
congured 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.
The following shows the dierence between Link MTU and IP MTU.
Layer 2
Overhead
Link MTU and IP MTU Delta
Ethernet
(untagged)
18 bytes
VLAN Tag 22 bytes
Untagged Packet
with VLAN-Stack
Header
22 bytes
Tagged Packet with
VLAN-Stack
Header
26 bytes
portmode hybrid
To accept both tagged and untagged frames, set a physical port or port-channel. A port congured this way is identied as a hybrid
port in report displays.
S4820T
Syntax
portmode hybrid
684
Interfaces