Questions tagged [ethernet]
Ethernet is the most common set of standards for wired connections in local area networks.
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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 ...
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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 ...
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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?
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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?
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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 ...
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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 ...
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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 ...
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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.
...
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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.
...
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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/...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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How to test cat5/cat6 cable runs, using software-only, or simple tools? [closed]
Are there any utilities or simple tools or techniques to easily test a CAT5 cable, to see how well was it installed?
Cat5 is often installed by amateurs, but has been installed and "working" for ...
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Direct ethernet link between two servers
Say I had two servers which needed super-low latency (Database, file etc.). Would it be possible to directly connect the two servers with 10GbE, so each server had 1 (in the real world it would have 2)...
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eth0 NIC Link is Down repeating message in kernel log
I've noticed since few days ago that same repeating kind of messages occurs and I positively can say that nothing was intentionally changed (installed/uninstalled) in that period.
here's sample of /...
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Where are ethernet errors logged?
Munin is showing me a graph like this:
During that spike, I was unable to access my server through the eth0 port (I could access it through my IPMI port).
I'm trying to figure out what happened, ...
14
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Ethernet port plastic plug blocking port access on server
I have Dell Poweredge server with plastic blockers inside their ethernet ports. My problem is that I don't know how to take it out. You can see photo of the plug here:
I tried to pull them out, or to ...
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1
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What am I misunderstanding about calculating MTU?
Okay, I just finished resolving a jumbo frames issue between a few Xserves, a Netgear GSM7224, and a Drobo B800i. It turned out that the Xserves (Mac OS X 10.6.8 Server) and the Drobo B800i accept the ...
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What happens when ARP Request comes from a different subnet?
What will happen when an ARP Request packet is sent from router1 to router2 in the following two cases? Will an ARP Reply be generated or the ARP Request packet be dropped?
[router1]Intf1(20.0.0.1/...
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A "splitter" is plugged into a patch panel... how does this still work?
I found a patch panel that splits off ethernet into multiple hosts as shown below.
Can anyone explain how this might work?
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Why does ethernet have a minimum frame size specified?
I think the minimum is 64 Bytes. Why is that minimum necessary?
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What are the differences between channel bonding modes in Linux?
Under Linux you can combine multiple network interfaces into a "bonded" network interface to provide failover.
But there are several modes, some of which do not require switch support. I'm not ...
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Which OSI-Layer does Ethernet belong to?
Just wondering.
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What is, and what problems result in a 'carrier error'
I haven't found a really clear definition about what a 'carrier error' is within the context of the ifconfig output for a interface. I have been searching on Google and there really isn't a great ...
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How does BER compare between different 10GbE physical media?
I am under the impression that you should use optical for 10GbE networking because of a BER (bit error rate) several orders of magnitude lower than copper.
I'm pretty sure I previously found ...
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Why straight-through ethernet cables?
I was explaining the difference between straight and crossover cables to my friend, and began wondering why on earth the early designers thought it was a good idea to use two different cable types?
...
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What is the disadvantage to cascading multiple switches?
I have to wire a new office for ethernet and the contractors want to charge atrocious amounts for each line running to each room in the office. It will be much cheaper for me to run a single line to ...
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Does a single LACP channel over multiple switches increase redundancy?
I am curious for opinions, findings, or evidence that having multiple interfaces bonded using LACP to ports in multiple switches can increase redundancy. Previously bonded interfaces have always been ...
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How Many Ethernet Ports Can I Plug into a Single Computer
Given the fact there are Quad ports PCI/PCI express cards out there, I wonder how many of them (x4) can I plug into a single server?
Perhaps the capacity bottleneck is the PCI bus, but I am not ...
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Why both T568A and T568B standards?
I've always wondered why there are the two different wiring standards for Cat5 UTP cabling. The only technical difference between the two is the green and orange pair are swapped, which accomplishes ...
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Which tool should I trust, mii-tool and ethtool don't show me the same values
Our hosting company provides all the switching infrastructure for our servers. The private network, connected to eth2 should be GbE. Recently I've been suspecting that something is misconfigured as ...
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10 gigabit networks: Decieding between fiber and twisted pair
With a green field installation 10gbps network (no legacy equipment to support), why would one select one physical medium over the other? If left to impulse, I'd probably go with fiber optics over ...
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Bridge to a used eth1 card without losing connection via that card
How can I set bridge between a real eth card on a remote machine without losing my ssh connection to that machine.
I ssh into a machine via its eth1 iinterface. 172.168.40.2 255.255.255.0.
I ...
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1
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Ethernet interface errors
My Ubuntu servers ethernet interface that connectes to ISP's multiplexer shows errors. Here is the snapshot:
RX packets:204564288 errors:3193970 dropped:0 overruns:0 frame:3138402
...
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What Ethernet twisted pair cable is best with a particular Ethernet switch
tl;dr I want the appropriate Ethernet cable for my Ethernet switch. How do I correlate Ethernet cabling speeds measured in hertz with an Ethernet switch "speed" measured in bits-per-second ...
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Why WakeOnLAN frames are sent to broadcast
I'm trying to figure out why wake on lan frames, in the simplest form, are designeted to the ethernet broadcast address (FF:FF:FF:FF:FF:FF) and not to the address of the machine to be powered on.
...
9
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Cut network cables in Cisco 2960 PoE
We've a Cisco 2960e that services our VoIP phones and other things. I inherited it.
The question I have is the cut cables: there are about four network connectors that are cut about 1cm away from the ...
9
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1
answer
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LAN: What are the things to look at when arriving in a new place
My company is moving to a new place, and the only thing I know about the cabling is that there are cables and a patch panel. I have no idea about the cable speed, quality, and I'm a software guy with ...
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How to test/debug bad network wiring?
I recently bought a place already wired with Cat 5E (8 ports, leading to a central closet). However attempting to get link, nothing works. On closer examination, it was obvious that the ends in the ...
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Cheapest way to remotely control 120v outlet via ethernet? [closed]
What is the cheapest solution to be able to remotely power cycle a regular 120V outlet via ethernet? I've seen solutions like iBoot, but they're really expensive. Is there a cheap way to remotely ...
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Is it possible to match an internal IP address to a switch port?
I'm trying to find a computer that has a certain IP address on our internal network. I have identified the computer name from DNS, but in this case it does not help me.
Just wondering if I can ...
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Ethernet frames: what are the source and destination MAC addresses?
Imagine you have some network configured like this
+-----+ +------+ +------+ +-----+
|comp.|---|bridge|---|router|---|comp.|
| A |---| B |---| C |---| D |
+-----+ +------+ ^ +------+...
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How to fix the wiring mess that is my server room
So, I have inherited a mess of a server room.
Rack 1: 5x 48 port patch panels; 140 in use | 3x 48 port switches
Rack 2: 4x 48 port patch panels; 120 in use | 3x 48 port switches
Rack 3: 3x 48 ...
8
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1
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Can a limited broadcast packet contain destination MAC address other than FF:FF:FF:FF:FF:FF?
Can a limited broadcast contain destination MAC address other than FF:FF:FF:FF:FF:FF?
If the answer is true, could you provide an example of a protocol that uses a packet like this.
Ok, to elaborate ...
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0
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Shocking ESD damage, what more can be done? [closed]
Today, over $6,000 in networking equipment was destroyed. Remarkably, the main circuit SPD, power strips and APCs are fine. Ethernet seems to be the method of surge transmission, as everything ...
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What is a good default IP address?
My company makes Ethernet devices. These devices have very little I/O. No keyboard, no video output. When the customer gets the device he must configure it for his network. I'd like to choose an ...
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Effect of heat on CAT5 Ethernet Cabling
I am wondering what the heat rating is on standard CAT5 cabling or where I can check the heat rating of my cabling by using the information inscribed on the cabling?
In my specific situation, I am ...