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Questions tagged [ethernet]

Ethernet is the most common set of standards for wired connections in local area networks.

Ethernet is the most common set of standards for wired connections in local area networks.

Originally designed in the 1970s, Ethernet had a data rate of 10 megabits per second. Later, Ethernet was extended to support rates of 100 megabits/second, 1 gigabit/second, 10 gigabits/second and 100 gigabits/second.

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How do VLANs work?

What are VLANs? What problems do they solve? I'm helping a friend learn basic networking, as he's just become the sole sysadmin at a small company. I've been pointing him at various questions/answers on Serverfault relating to various networking…
Murali Suriar
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Should network hardware be set to "autonegotiate" speeds or fixed speeds?

We recently had a little problem with networking where multiple servers would intermittently lose network connectivity in a fairly painful-to-resolve way (required hard reboot). This has been going on for about two weeks, seemingly at random, on…
Jeff Atwood
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How to check the physical status of an ethernet port in Linux?

I want to check if a specified ethX is physically up or down. How do I do that with the command line?
Jader Dias
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Why do ethernet cables have 8 wires?

This might seem a stupid question but why do Ethernet cables have 8 wires? Cat5 cables were just using 4 of the 8 wires, so only 4 are actualy 'needed'. Why not 12 or 16 wires?
ProgrammerAtWork
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e1000e Reset adapter unexpectedly / Detected Hardware Unit Hang

I have a Dell 1U Server with Intel(R) Xeon(R) CPU L5420 @ 2.50GHz, 8 cores running Ubuntu Server Kernel Version 3.13.0-32-generic on x86_64. It has dual 1000baseT networking cards. I have it set up to forward packets from eth0 to eth1. I have…
Kyle Coots
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What is the "in-the-wire" size of a ethernet frame? 1518 or 1542?

According to the table here, it says that MTU = 1500 bytes and that the payload part is 1500 - 42 bytes or 1458 bytes (<- this is actually wrong!). Now on top of that you have to add IPv4 and UDP headers, which are 28 bytes (20 IP + 8 UDP). That…
chrisapotek
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What is this wiring panel and what are these Ethernet "ports?"

In my office's building there is a stone-age LAN rack with some Ethernet ports I've never seen before. I need to find the name of this ports, if they have one, and then buy some cables or adapters. Unfortunately, I'm not allowed to dismount the…
Alessandro Cappello
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What's the Wireshark packet receiving and processing procedure on a Windows machine?

I am about to use Wireshark for some traffic monitoring on my Windows computer. While working on it, I was wondering how Wireshark manages to catch low level network packets before Windows does. First of all, a network interface on my NIC receives…
Hansi
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ARP broadcast flooding network and high cpu usage

Hoping someone here might have some insight to the issue we are facing. Currently we have Cisco TAC looking at the case but they are struggling to find the root cause. Although the title mentions ARP broadcast and high CPU usage, we are unsure if…
Cold T
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What is the clock frequency inside 10Gb and 100Gb Ethernet cards?

As I understand, a 10Gb Ethernet card is capable of putting 10Gb every second on (say) a fibre optics cable. Now naively, for this to happen in hardware, one will need a 10GHz clock running the network card. It is possible to half that frequency by…
Randomblue
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Best way to get the MAC of eth0?

Is there a more efficient way to retrieve the MAC address of a NIC in Linux? This works: ip link show dev eth0 | awk ' /link\/ether/ { print $2 }' but can it be found via something like: cat /sys/net/something
brodul
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How does Ethernet know how long a frame is?

Looking at the Ethernet entry on Wikipedia, I can't figure out how it's indicated how long the Ethernet frame is. The EtherType/Length header field apparently can indicate either a frame type or an explicit length, and I'm guessing that in the case…
dirtside
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What can cause network packets consisting of PUU?

We have a system which is suffering from comms outages on a gigabit ethernet network. The traffic load on the network is such as to slightly stress a 100Mb network, but there are gigabit switches and NICs and cables throughout - or so I am told by…
AlastairG
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Is one 10 gig port the same as ten 1 gig ports

I've been asking me this for a couple of days and after a bunch of searching I wasn't able to come up with a comprehensible answer, not even a theoretical one that makes sense in my head. I'm playing around with solutions for Mac hosting and I was…
Constantin Jacob
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What's the difference between a bridge and a switch?

I can't find any authoritative source that can concisely explain the difference between a bridge and a switch. As far as I can tell, most devices commonly referred to as "switches" fit the description of "bridge" as defined by the IEEE 802.1D…
Dan Moulding
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