Users Guide

Table Of Contents
Port Characteristics 633
Auto-Negotiation
Dell EMC Networking N-Series switches implement IEEE 802.3 auto-
negotiation for 1000BASE-T, 1000BASE-X, NBASE-T and 10GBASE-T based
copper interfaces. 1000BASE-X fiber interfaces also implement auto-
negotiation. Auto-negotiation is required to be present and enabled for
1000BASE-T, NBASE-T, and 10GBASE-T copper interfaces in order for a clock
master to be selected.
The administrator can configure the advertised capabilities, including the
acceptable link speeds, or may disable auto-negotiation altogether. Auto-
negotiation must be disabled and full-duplex must be enabled on certain
fiber interfaces. However, 1000BASE-X fiber interfaces require auto-
negotiation to be enabled. Disabling auto-negotiation on copper interfaces is
not recommended as it can lead to a configuration mismatch, where one or
both interfaces may appear to come up but, in fact, they have not agreed on
the speed, duplex, or clock master. This may occur when the devices are
connected as follows:
One end is set manually to half-duplex and the other is manually set to
full-duplex
One end is set to auto-negotiation and the other is manually set to full-
duplex
Both sides are manually set to full-duplex, with one side set to auto-
negotiate with the link partner and the other side configured with auto-
negotiation disabled.
Maximum Transmission Unit
Dell EMC Networking N-Series switches allow the operator to configure the
maximum transmission unit for the switch to a value larger than the IEEE
802.3 standard allows. This jumbo frames technology is employed in certain
situations to reduce the task load on a server CPU and to transmit large
amounts of data efficiently. The need for jumbo frames predominantly
appears where certain applications would benefit from using a larger frame
size (for example, Network File System (NFS). The larger frame size reduces
the number of headers transmitted per unit of data, leading to greater
throughput. The Dell EMC Networking jumbo frames feature extends the
standard Ethernet MTU (Max Frame Size) from 1518 bytes (1522 bytes with