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 ...
0
votes
3answers
648 views

What is the difference between a hub and a switch?

I'm sneeking around online store for used stock of hubs, routers and switches for a project I have to build a network infrastructure. So far, I have bought: 1x Cisco 2514 Router; 5x Cisco Serial ...
2
votes
2answers
4k views

Fedora 17 ifconfig eth0 returns an error message, why did linux change eth0 to em1?

I have a fresh install of Fedora 17 installed, 64 bit. Everything works flawlessly, It connects to the internet automatically when I plug in the internet cable. So I'm kind of confused when I ...
76
votes
17answers
39k views

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 ...
4
votes
3answers
15k views

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 | +-----+ +------+ ^ ...
3
votes
2answers
4k views

How do I dynamically obtain IP addresses for VLAN interfaces?

I have an Ubuntu machine on which I have created four VLANs, namely eth0.100 ,eth0.200 , eth0.300 and eth0.400. I want to dynamically obtain the IP addresses using the DHCP server. It should provide ...
2
votes
1answer
1k views

Physical network setup for pfsense w/ CARP for redundant firewalls

So I'm looking at this diagram: http://doc.pfsense.org/index.php/Configuring_pfSense_Hardware_Redundancy_(CARP) Does this assume that the "DSL Router" at the top of the drawing has two physical RJ45 ...
0
votes
3answers
602 views

Bonding: works only for download

I would like to install bonding with 4 links with mode 4. but only "download/receiving" works with bondig. for transmitting the system chooses one link. ifconfig bond0 Link encap:Ethernet ...
0
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2answers
125 views

Raw 802.3 through ethernet switch

At work I have a bunch of devices that communicate to and from a computer using raw 802.3 ethernet. Communication to the devices is mediated by a little program a coworker wrote, which uses the ...
18
votes
3answers
11k views

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 ...
7
votes
6answers
19k views

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 ...
9
votes
1answer
2k views

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 ...
7
votes
5answers
11k views

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 ...
5
votes
3answers
2k views

Multiplexed 1 Gbps Ethernet?

Is it possible to multiplex two (or more) 1Gbps Ethernet into a single logical connection? Is it common place? Advisable? Stupid? Other considerations? I ask because my hosting partner's network ...
3
votes
4answers
7k views

Ethernet Loopback plug - running a ping

For a project at work, I need to be able to test various Ethernet NICs by connecting them to a "loopback adapter plug", like this one on various embedded Linux boxen that come off a production ...
10
votes
7answers
990 views

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 ...
8
votes
2answers
2k views

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 ...
4
votes
6answers
11k views

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 ...
2
votes
3answers
470 views

Ethernet: network topology

Consider a standard GigE network switch. In order to do the switching, presumably it needs to maintain a map of MAC addresses of all things that exist on the network to its (switch's) port numbers. ...
2
votes
5answers
2k views

Link aggregation with DSL and Ethernet, and different ISP's?

We're a webdev company that has outgrown its ADSL bandwidth. It's currently 4/1 Mbit/s and due to distance we can't simply get faster DSL, whether ADSL or SDSL. Stacking multiple DSL connections is ...
2
votes
7answers
375 views

How to separate the display and peripherals from the actual computer?

I am trying to see if its possible to toss all the computers in the server room and just run cables out of it. The end goal is you just sit down at your desk and all you have is a display and ...
1
vote
1answer
2k views

bridging two network interfaces in ubuntu linux 12.10 AND being able to access it from that machine

Ok, i have about had it but heres the deal. I have 7 total machines connected like this: [5 workstations]<--->ServerPC<---->MAINPC<---->router FYI, dont worry about the workstations they ...
1
vote
6answers
6k views

physical port locks for ethernet, USB, phone, etc.?

If a user or a visitor sees a port, they will try to stick something into it and then complain to us when it doesn't work or breaks their stuff. Are there such things as physical locks that can be ...
4
votes
1answer
172 views

Surge protection for outdoor network cable run [closed]

I'm going to have a network cable run between floors of a home, and most of the run will be outdoors, up the side of the building. I ordered a spool of shielded UV-rated waterproof Cat6 cable. From ...
4
votes
3answers
1k views

Effect of reversing a pair, in cat5 cabling (e.g. swapping stripe and solid)

Is there any practical effect of reversing solid and stripe, when wiring cat5 cables? But if I've got a cable where each pair is a pair but one end is flipped, will this make any practical difference ...
3
votes
1answer
264 views

Missing Ethernet preamble [closed]

I am helping my colleague debug his problem. Basically, there are two 10M devices, and only one of which we have control over (the other being a "black box"). Analyzing the Ethernet hardware signals ...
1
vote
3answers
4k views

Can Wireshark capture an entire Ethernet frame including preamble, CRC and Interframe spacing?

I am examining an Ethernet frame in Wireshark. According to the "Ethernet frame" Wikipedia article and accompanying diagrams, "A frame starts with a 7-octet preamble and 1-octet start frame delimiter ...
1
vote
2answers
510 views

ethernet cable is connected but It shows unplugged [closed]

I told datacenter too connect two of my servers with a crossover cable to each other. But when I try this command ethtool eth0 Settings for eth0: Supported ports: [ TP ] Supported ...
0
votes
1answer
27 views

How to diagnostic internet access failure on a linux system?

I have a VM running on Xen. The virtual machine was running fine for months and suddently the network access broke down. Dom0 DomU .-------. bridge ...
0
votes
4answers
689 views

Ubuntu is showing weird HWAddress for eth0 after a power failure

Recently, my ubuntu box encountered a power failure. After rebooting, the HWAddress of eth0 is showing a very weird number: 00:00:00:00:00:30. I have tried sudo ifconfig eth0 down & sudo ifconfig ...
-1
votes
2answers
81 views

Lightning/surge risk of Ethernet cable run inside an exterior wall [closed]

In a previous question, I had planned a Cat6 (Ethernet) cable run outside a home, adjacent to a coax run. I was advised against it, and I'm interested in taking that advice. Now I'm considering ...