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

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1answer
102 views

daisy chained layer 2 [closed]

I just read an article about how daisy chaining switches is bad, that one should always do an Ethernet drop directly to the main switch rather than passing by the others, because power issues will ...
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2answers
146 views

What do I request from the LAN upgrade contractor to avoid simple oversights? [closed]

The company for which I work have allowed me to hire a LAN wiring contractor to completely overhaul the building LAN. Currently there are old 10MBit Ethernet cables and switches running and I ...
0
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1answer
151 views

Routing traffic externally instead of internal loop

I have one Ubuntu box with 2 network cards. I am running netperf on the computer to measure performance of networking equipment, ethernet coming out of eth0 into the switch then back out into the ...
1
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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
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2answers
549 views

New EFM leased line setup with Watchguard router, vlan tagging issue

I have recently had a 2mb EFM connection installed in a charity I work for. We were not supplied a router because we already had a watchguard XTM330 in storage ready to be used. The line is presented ...
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1answer
54 views

What network traffic when ethernet plugged in [closed]

So in a general sense (e.g. not windows, linux specific) what network traffic is generated when I first boot up/plug in a network cable. Basically: Detect DHCP server Pull an IP Address from DHCP ...
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3answers
3k views

How do I connect to and access a Cisco router?

I'm a total newbie to Cisco and I have a cisco router on which I have to do some experiments. How can I access this router? Ports available are Ethernet 0/1, Ethernet 0/0, Console, Aux. I guess if I ...
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3answers
2k views

Enabling jumbo frames on switch but not on devices: looking for trouble?

The switch at hand is a Dell PowerConnect 2716 which does support both VLANs and Jumbo Frames but, as far as I can understand from its manual, it only has a global Jumbo enable/disable setting and no ...
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1answer
626 views

Changing the default gateway address in Centos

I have a a Centos PC with 2 IP addresses. One of them is because of a back to back connection with another PC, so both run on different subnets. The eth0 has the 192.xx.xx.xxx address and eth2 has ...
3
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2answers
81 views

Autonegotiation on laptops for mobile users a must now?

I work in Unified Communications for a company with about 9000 desktops and laptops. I'm part of a team who is implementing and supporting things like Lync and Jabber Video and audio conferencing. ...
3
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2answers
311 views

Why is there an EtherType for SNMP?

Today I was reading through some documentation about the fundamentals of networks (IP, Ethernet, MPLS, ...). And while looking at the Ethernet Types that can be used in the Ethernet Frame I saw there ...
0
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2answers
1k views

Mismatch between IP address and MAC Address

Suppose you have two interfaces in the host belonging to the same subnet connected to a normal L2/L3 switch port which has a single vlan with interface IP 10.0.0.1. nxge0 (10.0.0.201) ...
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2answers
314 views

Analyse custom Ethernet frame with WireShark

WireShark can conveniently dissect Ethernet frames, and tell you exactly what each byte means. For example, it tells you where the TCP/IP headers are, how they have been populated and if the checksums ...
1
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0answers
2k views

Is it possible to mix jumbo frames VLAN and standard mtu VLAN on the same switch port?

If a managed switch and all attached devices both support VLANs and Jumbo Frames, is it possible to mix VLANs with jumbo frames and VLANs with standard frames on the same switch port / ethernet card? ...
37
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6answers
30k views

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?
3
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1answer
519 views

Hyper-V Virtual Machine Networking issues related to Max Ethernet Frame Size

I fixed an issue today earlier today but i'm interested in learning WHY it worked. We set up a new Hyper-V virtual machine only to discover that HTTP traffic wasn't working. HTTPS, pings, everything ...
2
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1answer
1k views

Packet drops after configuring Ethernet Bonding

I am trying to configure Ethernet bonding for our servers . Both the Ethernet interface in my server are connected to two different network switches physically. Looks like my Ethernet bonding ...
3
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3answers
13k 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 ...
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2answers
134 views

What is the fastest way to connect two machines for a ping-pong test? [closed]

I need to do a latency test between two machines, basically a ping-pong packet test. I wonder what is the fastest connection I can have between those two machines. I imagine my options are: Ethernet ...
3
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2answers
3k views

Why is the link between my switch and my router always negotiating half-duplex mode?

I have a Cisco 2950 switch which has one of its ports connected to an Internet router provided by my ISP; I have no access to the router configuration, but I manage the switch. If I leave all switch ...
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1answer
118 views

What would cause a wired vs wireless speed difference of 16mbps vs 9 mbps? [closed]

Tested via speedtest.net I've set my wireless router to be b/g/n mode (there's no n-only mode on my router). And I am using a USB stick (N, not G) on on PC and an internal wireless on another ...
0
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3answers
577 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 ...
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2answers
1k views

ifdown em1 Users cannot control this device. Allow users to control em1 device

I want to allow users to control the em1 device in Linux: When I run this command: ifdown em1 em1 is the embedded ethernet card 1, I want the user to be able to turn off the ethernet card. On ...
2
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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 ...
7
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1answer
5k views

How do I poll the ARP table with an SNMP OID?

When you need to poll the ARP table of a device, conventional wisdom is to use ipNetToMediaPhysAddress or atPhysAddress; however, both of these OIDs are deprecated according to Cisco's documentation. ...
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2answers
475 views

Is TCP/IP encapsulation MSB or LSB?

Application data sent over TCP experiences multiple encapsulations: The application data is encapsulated within one or many TCP fragments The TCP fragment is encapsulated within one or many IP ...
7
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3answers
4k views

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 ...
8
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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 ...
3
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1answer
126 views

Two network cards latency

I'm trying to setup a network architecture where one network is a low-latency low-bandwidth tcp control system (GBit), the other is a high-bandwidth udp (maybe tcp) network that could get saturated ...
0
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1answer
478 views

arp across subnets which devices can be detected?

i have some devices connected in the same physical network (LAN) but in different subnets. I want to detect them all with the ARP from my computer. My Computer is also in the same physical network but ...
1
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1answer
6k views

Can't start eth1 and dhcp on debian wheezy

What I want: eth0 is connected to internet and has a static IP-address. eth1 connected to internal network and be a dhcp server for subnet. But I can't get eth1 to work. Error: $ ifup eth1 ...
5
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1answer
2k views

Client not getting address from some DHCP server

I'm working on some embedded devices which should be connected to a large network (hundreds of devices) via ethernet and that should be configured using the DHCP protocol. What I'm experiencing is ...
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2answers
5k views

Difference between ethernet switch and ethernet pass-through

Most blade server systems can have an ethernet switch module or an ethernet pass-through module. What is the difference between both? Is the pass-though module simply "dumb" as a hub? Why would you ...
1
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1answer
1k views

Why is there no autonegotiation for ethernet jumbo frames? [closed]

Having read up a bit about ethernet jumbo frames, I'm wondering. There seem to be technical advantages to being able to use larger than 1500 byte ethernet frames in some cases. Just enabling jumbo ...
2
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2answers
7k views

How to test cat5/cat6 cable runs, using software-only, or simple tools?

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 ...
9
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1answer
296 views

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 ...
3
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1answer
218 views

Server ethernet bridging, fail-safe [closed]

Is there server hardware available with two ethernet ports, that can turn into a fail-safe bridge when offline? My use example is a server that does filtering and traffic monitoring on an ethernet ...
6
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1answer
717 views

FCoE, on any Ethernet switch?

I understand the concept of FCoE. I have looked at the Wikipedia page and looking at the layer 2 frame diagram, it looks like FCoE really should "just work" on any Ethernet switch, but is this really ...
0
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1answer
326 views

How to setup an Openvpn server with two gateways to internet

I have an openvpn server behind two wan interfaces: eth1 and eth2 where eth1 is the default gw and eth2 is where openvpn binds to. The problems my ovpn server is replying back to ovpn client via the ...
18
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2answers
10k 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 ...
1
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1answer
169 views

Freebsd how detect ethernet loopback on interface

I have network based on stupid hubs. And freebsd router in center of this network. Today i see in 'systat -vmstat' : Interrupts 8005 em1:rx 0 That was a loop on one hub. Is there any way to ...
4
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3answers
1k views

Can our firewall detect traffic sniffing inside the network?

We use Cisco ASA's firewall and NAT functions in our network (200 computers). Is there any possibility to configure Cisco ASA to detect traffic sniffering (for example wireshark) and network ...
0
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1answer
140 views

Protect software default gateway from ip-stealing

We have a corporate network that is comprised of the following elements: Internet cable (wall) <-> (ext interface (DHCP))(Windows Server 2008, TMG-enabled, Internet Gateway)(int interface (static ...
5
votes
1answer
2k views

Can WireShark detect Ethernet PAUSE packets on network when running on Windows?

We have a Windows server which is connected to a switch processing a large quantity of data. We noticed that when we disabled FlowControl on the network adapter, that it appeared that we were getting ...
0
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3answers
5k views

Dell PowerConnect Console connection via Ethernet

When you buy a Dell PowerConnect (In my case it's a 5548) you are given a console cable that is serial to ethernet. Let's say you don't have a serial port on your laptop and but you still want to run ...
0
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3answers
204 views

Power-over-Ethernet: Designing PSD with less than 48V?

I want to use Power-over-Ethernet for an IP Camera. On the host-side, which also is the PSE (Power Sourcing Equipment) I have my own hardware. On this hardware I just have 12V of supply voltage. ...
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2answers
3k views

testing signals on an ethernet cable

I work on escalators that use ethernet cables to send signals from "nodes" to a PLC. the only tool available is a Fluke multimeter. is there a way of reading these signal using the meter? or do I need ...
12
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1answer
983 views

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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1answer
392 views

What is the minimum and maximum size of an Ethernet frame with split up

How do I calculated the minimum and maximum size of an Ethernet frame with split up.We all know maximum size for Ehternet frame is 1518bytes but would be the with split up?
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2answers
194 views

Transparent round-robin scheduling of multiple network interfaces without bonding

I have a server communicating with a cluster of machines and the bottleneck is the network bandwidth. The good news is there are 2 interfaces, while the server can only make use of one. Without ...