Deployment Guide

The following table lists the various Layer 2 overheads found in the Dell Networking OS and the number of bytes.
Table 26. Layer 2 Overhead
Transmission Media MTU Range (in bytes)
Ethernet
594-12000 = link MTU
576-11982 = IP MTU
Conguring wavelength for 10–Gigabit SFP+ optics
You can set the wavelength for tunable 10–Gigabit SFP+ optics using the wavelength command. To set the wavelength, follow these
steps:
• Enter the interface mode and set the wavelength.
INTERFACE mode
wavelength 1529.0
The wavelength range is from 1528.3 nm to 1568.77nm.
• Verify conguration changes.
INTERFACE mode
show config
Converting a QSFP or QSFP+ Port to an SFP or SFP+
Port
You can convert a QSFP or QSFP+ port to an SFP or SFP+ port using the Quad to Small Form Factor Pluggable Adapter (QSA).
QSA provides smooth connectivity between devices that use Quad Lane Ports (such as the 40 Gigabit Ethernet adapters) and 10 Gigabit
hardware that uses SFP+ based cabling. Using this adapter, you can eectively use a QSFP or QSFP+ module to connect to a lower-end
switch or server that uses an SFP or SFP+ based module.
When connected to a QSFP or QSFP+ port on a 40 Gigabit adapter, QSA acts as an interface for the SFP or SFP+ cables. This interface
enables you to directly plug in an SFP or SFP+ cable originating at a 10 Gigabit Ethernet port on a switch or server.
You can use QSFP optical cables (without a QSA) to split a 40 Gigabit port on a switch or a server into four 10 Gigabit ports. To split the
ports, enable the fan-out mode.
Similarly, you can enable the fan-out mode to congure the QSFP port on a device to act as an SFP or SFP+ port. As the QSA enables a
QSFP or QSFP+ port to be used as an SFP or SFP+ port, Dell Networking OS does not immediately detect the QSA after you insert it into
a QSFP port cage.
After you insert an SFP or SFP+ cable into a QSA connected to a 40 Gigabit port, Dell Networking OS assumes that all the four fanned-out
10 Gigabit ports have plugged-in SFP or SFP+ optical cables. However, the link UP event happens only for the rst 10 Gigabit port and you
can use only that port for data transfer. As a result, only the rst fanned-out port is identied as the active 10 Gigabit port with a speed of
10G or 1G depending on whether you insert an SFP+ or SFP cable respectively.
NOTE
: Although it is possible to congure the remaining three 10 Gigabit ports, the Link UP event does not occur for these ports
leaving the lanes unusable. Dell Networking OS perceives these ports to be in a Link Down state. You must not try to use these
remaining three 10 Gigabit ports for actual data transfer or for any other related congurations.
Interfaces 375