Reference Guide

– tx on: enter the keywords tx on to send control frames from this port to the connected device when a higher rate of

trac is received.

– tx off: enter the keywords tx off so that ow control frames are not sent from this port to the connected device when

a higher rate of trac is received.

– negotiate: enable pause-negotiation with the egress port of the peer device. If the negotiate command is not used,

pause-negotiation is disabled.

NOTE: The default is rx o.

MTU Size

The Aggregator auto-congures interfaces to use a maximum MTU size of 12,000 bytes.

If a packet includes a Layer 2 header, the dierence 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 L2 header = 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.

Dierence between Link MTU and IP MTU

Layer 2 Overhead

Dierence between Link MTU and IP MTU

Ethernet (untagged) 18 bytes

VLAN Tag 4 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 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 the 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.

Interfaces