Users Guide
MTU Size
The Aggregator auto-congures interfaces to use a maximum MTU size of 12,000 bytes.
If a packet includes a Layer 2 header, the dierence in bytes between the link MTU and IP MTU must be enough to include the Layer 2
header. For example, for VLAN packets, if the MTU is 1400, the link MTU must be no less than 1422.
1400-byte IP MTU + 22-byte VLAN Tag = 1422-byte link MTU
The MTU range is 592-12000, with a default of 1554.
The table below lists out the various Layer 2 overheads found in Dell Networking OS and the number of bytes.
Table 10. Dierence between Link MTU and IP MTU
Layer 2 Overhead Dierence 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 congured 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 dierent 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 congured on the VLAN members.
For example, the VLAN contains tagged members with a link MTU of 1522 and an IP MTU of 1500 and untagged members with a link MTU
of 1518 and an 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.
Setting the Speed and Duplex Mode 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.
EXEC Privilege mode
show interfaces [interface] status
2 Determine the remote interface status.
Interfaces
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