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

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78
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2answers
80k views

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
739 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 ...
78
votes
17answers
49k 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 ...
17
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8answers
25k views

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 ...
3
votes
2answers
5k 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 ...
19
votes
4answers
15k 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 ...
8
votes
6answers
23k 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 ...
5
votes
1answer
4k views

Ubuntu Linux - two interfaces, same subnet, different vlan - MAC/ARP issues

I'm attempting to setup a server that needs to have interfaces on the same IP subnet, but different VLANs: eth1.102 Link encap:Ethernet HWaddr 00:50:56:b1:00:0f inet addr:10.1.1.6 ...
18
votes
5answers
41k views

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 ...
10
votes
2answers
5k 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 ...
10
votes
1answer
3k 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 ...
8
votes
5answers
16k 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 ...
6
votes
3answers
22k views

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 ...
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
8k 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 ...
2
votes
1answer
5k views

How do I increase the ring parameters for a NIC on a Linux server

I used the ethtool utility to increase the rx and tx values for the NIC on one of our servers. I ran the following command: ethtool -g eth0 Ring parameters for eth0: Pre-set maximums: RX: ...
10
votes
7answers
1k 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 ...
5
votes
1answer
763 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 ...
5
votes
6answers
17k 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
5answers
3k 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
1answer
2k 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 ...
2
votes
3answers
551 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
7answers
611 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
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 ...
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 ...
4
votes
3answers
2k 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 ...
1
vote
2answers
685 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
301 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
727 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 ...
0
votes
3answers
6k 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
votes
2answers
405 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 ...