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

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Tools to inspect an ethernet packet travels through host's interfaces?

I am debugging a local ethernet connection on a Linux machine. I want to inspect the ethernet packets as they travel. in and out current machines' interfaces. I do not have a GUI on the machine. Is ...
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3answers
308 views

Is it possible to cross-connect two AUI ports without transceivers?

Many Ethernet devices predating the ubiquity of RJ45 transceivers had DB15 "AUI" ports. One is ordinarily expected to attach a transceiver for either coaxial or twisted-pair Ethernet. Is it possible ...
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1answer
492 views

Understanding Ethernet Headers, What MTU Do I Need?

I see many articles on line stating that the overhead of Ethernet is 18 bytes (example: http://www.learnios.com/viewtopic.php?f=8&t=18887) Looking at this wiki article ...
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884 views

Internet slowed down because of SQUID Server setup

Recently I have setup a squid server for our office. I have computer (A) with two ethernet cards, one for internet and the second one for local networkIt has Ubuntu server OS with squid-server and ...
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1answer
173 views

Does using VLANs in your network infrastructure cause an appreciable decrease in performance?

This is something I've never considered before and wanted the opinions of the experts. We use VLANs day in and day out for various network tasks. My modus operandi is that in general, if something ...
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1k views

Linux bonded Interfaces hanging periodically

I've several hosts that are showing problems with connectivity. When working from the command line, for example, typing is frozen for a second or so, then recovers - then it does it again. The most ...
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4answers
690 views

Trunk fiber ports on switches

We are planning to purchase new switches for our network. We have three buildings in the same area that are all connected by fiber. Our main building is very large and needs to be connected by fiber ...
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1answer
2k 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 ...
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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 ...
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1answer
120 views

Linux network adapter keeps changing settings

I'm running CentOS 5 and noticed for the past week that eth0 settings keep changing and I have to reset them. Any ideas what it might be or where I need to start?
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1answer
187 views

Can a host launch a DOS attack on Ethernet?

Here is my trail of thought: Since Ethernet works on the principle of CSMA/CD one can possible setup a rogue host which transmits packets all the time forcing other to exponentially back off until ...
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Serial to ethernet cable: how to connect to device

How can I use a serial to ethernet cable to connect to a device: in my case a Hp ProCurve AP? A serial to USB or serial to serial would have been great but I found this serial to ethernet cable from ...
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2answers
270 views

Is it possible to wake a computer connected directly to its NIC?

If two computers are connected by ethernet directly (ie, with no router between them) can one computer wake the other using the magic packet? I ask because it's not working for me and I'm not getting ...
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1answer
2k views

How to troubleshoot the suspected ethernet card failure [closed]

Sometimes one of the laptop when attached to the dock would drop the ethernet connection. By constantly pinging the default gateway usually there are no packet drops but sometimes, it results in ...
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2answers
575 views

Ethernet over IP

I need to merge two L2 broadcast domain into single domain and I have to do this over unmanaged by me L3 IP network. All that I could find is vtun utility for linux. Which software&howto you can ...
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80 views

2 networks with a layer 2 bridge that shouldn't be there.

I have 2 separate networks that I manage. They have a router between and layer 3 connection is working fine. Last week my DHCP servers started handing out IPs across the networks, looking around I ...
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3answers
7k 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 | +-----+ +------+ ^ ...
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3answers
952 views

Phantom NIC issue causing eth0/1 to drop out

We are experiencing a very strange and frustrating problem. Our company has servers here in Massachusetts, as well as in California. The issues we are seeing are only on the CA hardware. Out in CA, we ...
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1answer
792 views

Why is half-duplex mode supported for 10BASE-T and 100BASE-TX networks?

I'm currently learning about Ethernet standards, auto negotiation and duplex mismatch. That made me wondering why half-duplex operations is allowed in 10BASE-T and 100BASE-TX networks. Wouldn't it ...
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1answer
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Solaris ethernet ports: e1000g1 and e1000g2 are not working

I can plumb and configure e1000g0 and e1000g3 using ifconfig, but I can't seem to make use of e1000g1 or e1000g2. When I try ifconfig e1000g1 plumb, I get ifconfig: plumb: e1000g1: Invalid argument. ...
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1answer
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My business computer doesnt connect to any ethernet device outside business lan [closed]

My computer which i use at work is within a domain. And our internet connection is through some kind of filter. So in Internet Explorer, there is a configured lan setting. When i try to connect any ...
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5answers
2k views

Virtual interfaces with default routes

My Ubuntu Server has one physical interface eth0. I want to assign 3 ip's (different subnets) to the server. I cannot use the default virtual interface creation tools like ifconfig or ip addr add ...
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1answer
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Accessing a connected device through LAN [closed]

I have a metered APC Power Distribution Unit (PDU) which is capable of spewing out the current load, power and such information through a LAN cable. I'm connecting the cable from the PDU to a server ...
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1answer
119 views

Netgear FVX538v2 slow whene connected to Canoga Perkins N525 ETSU

First of all thank you in advance for helping me. my issue is the old network admin found a problem whene he connected the firewall and the ETSU together the through put went down to less than 1 mega ...
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1answer
885 views

QLogic QLE8152 won't link up with a fiber loop

I have a Dell R710 running Debian Linux 6.0 (Squeeze). I installed a QLogic QLE8152 CNA in the PCI-E riser today and I have been trying to get the CNA's ethernet layer to come up after I put a fiber ...
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1answer
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Would the source and destination address in ethernet frame change?

Say there are 2 computers are connected this way in a wireless network: Computer A -> Access Point 1 -> Access Point 2 -> Computer B When a frame is sent from Computer A to Computer B, the frame ...
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348 views

How to determine the interface name for 2 Ethernet adapters with 8 ports?

I have 2 Ethernet adapters on a 2U server, each of them has 4 ports, for a total of 8 ports. Is there a way to find out the interface name(eth0, eth1 ...eth7) for each port without connecting to a ...
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387 views

Is a Router required to set up a network? [closed]

Is a router required to set up a network? Suppose I have just an Ethernet wire and then I fix it up to 3 computers. Can I then say that these computers are now in a network? If they are in a ...
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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 ...
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2answers
287 views

Two network adapters with the same ip

I have two network adapters that use the same ip range, but are different networks. I tried this but it didn't work: iptables -t nat -A OUTPUT -p all -d 1.2.3.0/8 -j DNAT --to-destination ...
9
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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 ...
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1answer
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Two network Macs have slow internet

I work in a boutique advertising agency as a web developer. I have my own servers at home for my website. In our office, we have 8 Macs. Two of the iMacs are against one wall with an ethernet cable ...
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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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266 views

Ethernet link negotiates a connection only in half duplex mode

I have a NIC which is capable of 100BaseT/Full. But it negotiates a connection only on 100baseT/Half mode. Here is the output of mii-tool: eth0: no autonegotiation, 100baseTx-HD, link ok The ...
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2answers
937 views

Ubuntu Server, 2 Ethernet Devices, Same Gateway - Want to force internet traffic through 1 device (or at least allow it to work!)

I have a Ubuntu 10.04 Server with 2 ethernet devices, eth0 and eth1. eth0 has a static IP of 192.168.1.210 eth1 has a static IP if 192.168.1.211 The DHCP server (which also serves as the internet ...
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Server can only make outbound connections

My server is running Ubuntu 10.04 and is connected by ethernet to a router/modem device. The problem is that it's basically ignoring incoming connections. So I can't SSH into it or access the ...
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Descriptions of Ethernet register/counter names?

Is there a manual/datasheet/some other resource that explains what do all these counters in ethtool -S <interface> mean? Some of them are self-explainatory, some aren't... I'm taking them from ...
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2answers
195 views

Intel Server Board: Ethernet MT connection vs PM connection

What's the difference between an MT ethernet connection and a PM ethernet connection? Intel server board has two ethernet ports that are named in that manner.
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391 views

Carrier ethernet vs Metro ethernet or any other alternative?

We have three remote offices (office A, B, and C), two (Office B and C) of them need to access the Linux file server and web application server in Office C. We also need to administer the network of ...
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1answer
333 views

Programatically extracting interface configuration from the system?

I would like to produce a list of all the interfaces available on a [Linux] system, and for each interface, produce a list of available IP addresses. I was hoping to do this in a more graceful ...
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1answer
342 views

Multi-NIC Linux machine's NICs are responding to each other's ARPs regardless of arp_filter setting

I have an old Linux machine running a 2.4.37 kernel. In the machine are two NIC cards both on the same network with different IPs. For some testing, we want each IP's traffic routed through that NIC, ...
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4answers
140 views

Linux - Is there a way to determine what mac addresses an interface has seen traffic from?

Yes, I know about ARP but that relies somewhat on IP layer connectivity in that the remote system must be configured with an IP on a recognized subnet. Is there any way to just dump off what mac ...
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Is there a device or piece of software that can act as a transparent Ethernet bridge and limit bandwidth on MAC by MAC basis?

So for example, it will only let a particular MAC address on side A use 100kbps in ether direction.
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1answer
5k views

How do I configure a USB ethernet adapter under CentOS 5.3?

I've got a server running CentOS 5.3 (Final; kernel version 2.6.18) which I need to add a 2nd NIC to, initially temporarily, but eventually permanently. I'm not familiar with installing drivers under ...
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3answers
1k views

interface id for ethernet card

My PC (CentOS)has one ethernet card 1, linked to the internal company network for internet surfing etc., and another ethernet card 2, linked with an embedded device for programming. Each time, when ...
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3answers
531 views

SBS 2003 loses Connection to specific clients if not running Ping -t

I have inherited a client running SBS 2003 R2 and a mix of WinXP and Win7 clients. All machines have the latest updates. I started getting complaints that 1 or more computers would 'drop off' the ...
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How can I troubleshoot APIPA (169.254.x.x) in physical network cabling?

all: We have just started using an existing Cat5e cable to run 100Base-T to a new office, but unfortunately, machines in the new office see link but receive an APIPA address (169.254.x.x). I brought ...
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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 ...
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565 views

Virtual Ethernet Adapter / Multiple MAC and IP address for one adapter

I need to emulate multiple (10+) Ethernet adapters (different MAC and IP, same subnet) through a single Ethernet adapter. I know you can assign multiple IP addresses to a single adapter, but haven't ...
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217 views

Can't set up FC HBA with DHCP

I've got IP over FC working, and have the HBA (QLogic QLA2340) connected to a router with a DHCP server on it. However, whenever I do a: ifconfig fcip0 dhcp start I get: ifconfig: fcip0 wait timed ...