How to Directly Connect Two 10Gb Devices

Can you directly connect two 10Gbit devices? I recently picked up a pair of refurbished Intel 10GbE SFP+ NICs with the intention of upgrading my home-lab to 10gig. Not wanting to purchase an expensive 10Gb switch I was looking for ways to directly connect my server to my storage box. SFP+ supports many different transmission media, such as fiber, twinax, or even SFP+ to RJ45 adapters to just use good ol base-T networking. In the datacenter I love the simplicity of DAC cables - they already have transceivers and the cabling, no need to do anything but plug them in and go. But what about directly connecting two endpoints without a switch in the middle?

Reading through Wikipedia I realized twinax cables are... well... twin axial - meaning two, vs coax being one. Instead of finishing the paragraph (which would have answered my question) I decided what the heck, lets just plug them in and see what happens. I am happy to report there is no such thing as a crossover or straight-through twinax cable like there is in the Base-T world. All DAC cables are already cross over - meaning the receive line on side A is the transmit line on Side B and visa-versa. No need for a router or switch between 10GbE devices, just plug 'em in, configure their IP addresses and you are good to go.

So yes, you can directly connect two 10GbE devices that are SFP+ connectors to each other using DAC cables. This would be true regardless what you decide to call your cable, SFP+ copper, DAC, twinax, 10gig twinax, 10GbE copper, etc. All can be directly connected between two devices. No need to hunt ebay or craigslist for some expensive 10Gb switches.

*disclaimer* This document and presentations are my own and does not represent anything from any other entity. I will not be held liable for anything bad that comes of it.

Written by Eric Wamsley
Posted: August 30, 2020 10:26am
Topic: Networking
Tags: Networking,

 ©Eric Wamsley - ewams.net