Networking refers to the technologies and techniques that enable the interconnection of devices and applications allowing them to communicate electronically.

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58
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6answers
477k views

How to determine the hostname from an IP address in a Windows network?

My LAN has 50 Windows hosts. At the Windows command line I try ping to get the IP address of a running Windows machine. The question is how to get hostname of a specific IP address in the same ...
21
votes
5answers
42k views

What is the best way to transfer a single large file over a high-speed, high-latency WAN link?

This looks related to this one, but it's somewhat different. There is this WAN link between two company sites, and we need to transfer a single very large file (Oracle dump, ~160 GB). We've got full ...
25
votes
4answers
60k views

Improving TCP performance over a gigabit network with lots of connections and high traffic of small packets

I’m trying to improve my TCP throughput over a “gigabit network with lots of connections and high traffic of small packets”. My server OS is Ubuntu 11.10 Server 64bit. There are about 50.000 (and ...
37
votes
8answers
11k views

Windows TCP Window Scaling Hitting plateau too early

Scenario: We have a number of Windows clients regularly uploading large files (FTP/SVN/HTTP PUT/SCP) to Linux servers that are ~100-160ms away. We have 1Gbit/s synchronous bandwidth at the office and ...
71
votes
1answer
13k views

What happens when you plug two sides of a cable to a single networking device?

What is likely to happen when you plug two ends of a network cable to a single switch/router? Will this create problems on the network, or just be ignored?
28
votes
4answers
73k views

VirtualBox: How to set up networking so both host and guest can access internet and talk to each other

I was wondering if someone could give me a simple guide on how to set up virtual networking in VirtualBox (4.0.2) so that the following scenarios work: Both Host and Guest can access Internet Host ...
27
votes
6answers
1k views

Top-like tool for IP traffic [closed]

I need to keep watch on how much bandwidth some connections are taking in a server, and I know I have seen a top-like tool for that before. However, I can't remember the name of the tool, and I'm not ...
22
votes
8answers
3k views

Dynamically blocking excessive HTTP bandwidth use?

We were a little surprised to see this on our Cacti graphs for June 4 web traffic: We ran Log Parser on our IIS logs and it turns out this was a perfect storm of Yahoo and Google bots indexing us.. ...
36
votes
4answers
126k views

Is it possible to change an “Unidentified Network” into a “Home” or “Work” network on Windows 7

I have a problem with Windows 7 RC (7100). I frequently use a crossover network cable on WinXP with static IP addresses to connect to various industrial devices (e.g. robots, pumps, valves or even ...
13
votes
4answers
12k views

What's the difference between a switch, a router, and a modem?

What's the difference between a switch, a router, and a modem?
29
votes
14answers
72k views

What is a patch panel?

What is a patch panel? How it is different from (layer 2) switch? EDIT: I think my primary question (and confusion) is this: Why don't network connections go straight to the switch? Don't we still ...
29
votes
6answers
3k views

What are .DS_Store files and why does OSX leave them on Windows shares?

Whenever I access windows shares from OSX 10.5 it leaves .DS_Store files on the remote filesystem. What are they used for, and are they necessary, and can they be prevented from being created?
9
votes
4answers
3k views

Methodologies for performance-testing a WAN link

We have a pair of new diversely-routed 1Gbps Ethernet links between locations about 200 miles apart. The 'client' is a new reasonably-powerful machine (HP DL380 G6, dual E56xx Xeons, 48GB DDR3, R1 ...
12
votes
1answer
4k views

VirtualBox cloned Ubuntu Server network error

I run a number of virtual servers on my network and I want to be able to easily clone base installations of Ubuntu Server. I use the VBoxManage command to clone the actual hard disk and I then create ...
6
votes
7answers
44k views

How to setup VPN on home network [closed]

I am a software developer. I travel and sometimes have a need to access my files at home and tweak other family members computers. I would like to connect to my home network via VPN and then RDP ...
45
votes
6answers
48k views

What is the difference between a managed and unmanaged switch?

I've seen some documentation discussing the use of an unmanaged switch. What is the difference in functionality/performance/etc. between an unmanaged and managed switch?
25
votes
10answers
16k views

Network cable color conventions? [closed]

Are there any color conventions for network cable? I'm talking jacket color here, not the color of the individual conductors. I've seen and used mostly grey and blue which is what's usually readily ...
16
votes
3answers
2k views

Troubleshooting Network Speeds — The Age Old Inquiry

I'm looking for help with what I'm sure is an age old question. I've found myself in a situation of yearning to understand network throughput more clearly, but I can't seem to find information that ...
29
votes
5answers
2k views

Is a Self Signed SSL Certificate a False Sense of Security?

Is a Self Signed SSL certificate a false sense of security? If you are being eavesdropped, the user will simply accept the certificate like he/she always does.
15
votes
4answers
2k views

How to Monitor Bandwidth usage in real terms

I have a small (windows) network with a few people on it. We have internet access via a BT router Generally things are all fine, but occasionally, we seem to experience a dramatic loss of ...
14
votes
5answers
7k views

I'm designing a system to handle 10000 TCP connections per second, what problems will I run into?

I have a relatively new 8-core box running CentOS. I would like to develop a stats server that uses TCP. It's very simple, it accepts a TCP connection, increments a counter and closes the connection. ...
13
votes
1answer
29k views

MySQL [Warning] IP address could not be resolved

I'm running MySQL5.6.3 on a CentOS 6.1 virtual machine running on Windows XP in VirtualBox. The network card is configured in bridge mode, so my physical & virtual machines share the same ...
7
votes
3answers
8k views

Recommended switch for an iSCSI implementation [closed]

We want to implement an iSCSI SAN and all of our testing has shown that we can implement this quite cheaply (Starwind target, refurbished HP Storage array). What concerns me is the throughput/latency ...
4
votes
4answers
8k views

“Primary” DNS when there are multiple network connections

I have a machine that has a LAN network connection, which is used for internet access. This machine also has to be connected to a VPN connection. When the VPN is connected, Windows seems to ask the ...
27
votes
5answers
4k views

Locate rogue DHCP server [duplicate]

Possible Duplicate: How do I find if there is a rogue DHCP server on my Network? I know this is a serious long shot, but here we go. In the past week or so, for users connected to a ...
19
votes
6answers
43k views

How can I list my open ports on Debian?

What is the command to display a list of open ports on a Debian server? I tried netstat -a | egrep 'Proto|LISTEN' but I would like something more specific that actually lists the port number.
18
votes
6answers
21k views

How do you avoid network conflict with VPN internal networks?

While there's a wide variety of private non-routable networks across 192.168/16 or even 10/8, sometimes in being thoughtful of potential conflict, it still occurs. For example, I set up an ...
17
votes
11answers
83k views

How do I find out which devices are on a network?

How do I scan a network to find out which devices are on it? (I'd be happy with a list of MAC addresses and IPs.) For example, lets say I'm at work and want to be sure that there are no unknown ...
10
votes
2answers
8k views

Unable to Share Data between Amazon EC2 Instances for Windows

I have two Amazon EC2 Instances running Windows Server 2003 and IIS 6.0. Both the instances are created in the same region and have the same Security Group. I enables icmp for all ports and connection ...
7
votes
3answers
6k views

TIME_WAIT connections not being cleaned up after timeout period expires

I am stress testing one of my servers by hitting it with a constant stream of new network connections, the tcp_fin_timeout is set to 60, so if I send a constant stream of something like 100 requests ...
7
votes
4answers
9k views

Should a webserver in the DMZ be allowed to access MSSQL in the LAN?

This should be a very basic question and I tried to research it and couldn't find a solid answer. Say you have a web server in the DMZ and a MSSQL server in the LAN. IMO, and what I've always ...
21
votes
2answers
9k views

What is the command to flash a NIC link light?

I remember using a command line tool to flash a NIC's link light to identify it. I can't remember for the life of me what it was.
18
votes
3answers
12k 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 ...
17
votes
2answers
961 views

What is the fall off of subsecond throughput on Ethernet Network Interfaces

On a network interface, speeds are given in term of data over time, in particular, they are bits per second. However, in the uber-fast world of computing -- a second is kind of a really long time. So ...
17
votes
4answers
15k views

Why can't I connect to Amazon RDS after setting it up?

So, I just created the Amazon RDS account. And I started an instance of database. The "endpoint" is: abcw3n-prod.cbmbuiv8aakk.us-east-1.rds.amazonaws.com Great! Now I try to connect to it from one ...
7
votes
9answers
3k views

LAN Between Buildings

Right now I have two buildings across the street from one another that both have typical consumer aDSL connections (something like 12 Mbs down/1 Mbs up). When I need to access resources on the other ...
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 ...
5
votes
1answer
7k views

Keepalived for more than 20 virtual addresses

I have set up keepalived on two Debian machines for high availability, but I've run into the maximum number of virtual IP's I can assign to my vrrp_instance. How would I go about configuring and ...
5
votes
5answers
7k views

How to get Wake-on-LAN working?

I have a PC behind a router with a dynamic IP address that I want to configure for wake-on-LAN. How do I send the magic packet to the PC? Do I configure my router to forward UDP port 6 to the PC? How ...
5
votes
6answers
1k views

Looking for an open source real-time network analysis program

Can somebody recommend an open source real-time network analysis program? What I'm looking for the program to do is display a graph of bandwidth usage by IP within our internal network that can ...
4
votes
2answers
11k views

What is the correct network configuration for a devStack VM (virtualbox)?

Usually when I setup a new Ubuntu VM, i keep the eth0 in NAT mode to get the internet & I add a eth1 interface in HostOnly mode so that I can ssh. But using this devStack guide : Running a Cloud ...
16
votes
1answer
248 views

Vendor whitepaper says: 5Mpps no prob. I'm already hitting a wall at 120kpps. Where's the bottleneck?

HP's whitepaper on their QLogic (fka Broadcom) NetXtreme II adapters, which includes the specific NIC that I'm testing, states (page 7) that their small packet performance for packets up to 256 ...
15
votes
4answers
17k views

How does Windows decides which DNS Server to use when resolving names?

What algorithm does Windows use to decide which DNS Server it will query in order to resolve names? Let's say I have several interfaces, all active, some with no dns server specified, some told to ...
13
votes
3answers
3k views

How are IP addresses actually assigned?

I'm having a hard time understanding how a governing body assigns IP addresses, companies use BGP to advertise those IPs, and how the internet works. Then, where the hell does DNS come in? Can ...
13
votes
4answers
25k views

Is there an equivalent command for 'init.d/networking restart' in OS X

From time to time, I've encountered issues with OS X clients' network connections (Wired and Wireless, Leopard/Snow Leopard) where nothing will fix the issue, until you reboot. Is there a ...
13
votes
4answers
28k views

System error 1219 has occurred

I am trying to connect to a remote server and deploy a service there, through a deploy script. I start by stating "Net use" and send the credentials for the server. But here I get system 1219 error: ...
11
votes
2answers
14k views

Windows Appending Domain Suffix To All Lookups

I have a reoccurring DNS problem that has been plaguing our users occasionally causing their laptops to appended our companies domain to the end of all DNS queries. The problem only occurs when users ...
10
votes
9answers
26k views

How to use a Tone Generator to trace a network cable

We have a tone generator kit for tracing network cables, but I am having trouble using it correctly. The tone generator end plugs into the network cable I am trying to trace, and then I assume I ...
9
votes
4answers
8k views

Max number of socket on Linux

It seems that the server is limited at ~32720 sockets... I have tried every known variable change to raise up this limit. But the server stay limited at 32720 opened socket, even if there is still 4Go ...
7
votes
3answers
2k views

Does routing distance affect performance significantly?

When I say routing distance, I mean on a global scale. For instance, if my target audience is in China, do I look for a host within China?