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

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44
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6answers
39k 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
14k 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 ...
23
votes
8answers
29k views

Does using a single cable to connect two switches create a bottleneck?

I realise this may be a stupid question for some, but it's something I've always wondered about. Let's say we have two gigabit switches and all of the devices on the network are also gigabit. If 10 ...
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.
18
votes
4answers
57k 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 ...
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 ...
12
votes
1answer
527 views

Under what circumstances is TCP-over-TCP performing significantly worse than TCP alone (2014)?

Many admins keep perpetuating - on ServerFault and elsewhere - how bad of an idea TCP-over-TCP is, e.g. in VPNs. That even the slightest packet loss will make one suffer from at least severe ...
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
7k 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 ...
13
votes
5answers
6k 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. ...
10
votes
3answers
805 views

Creative IP/subnet/dns schemes

I've only administered rather small networks (<=25 nodes). Usually I put the gateway .1, dns/proxy as .10, mail at .20, printers at .30-39 and so on and so forth. I never directly use IP addresses ...
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
2answers
7k 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 ...
40
votes
8answers
285k views

What does “TTL expired in transit” mean on a ping attempt?

We get the message “TTL expired in transit” when we try to ping to a server in a different network segment. When we run tracert, 4 ip addresses repeat themselves indefinitely: 14 60 ms 59 ms ...
20
votes
2answers
7k 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
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 ...
17
votes
2answers
918 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 ...
15
votes
6answers
18k 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 ...
13
votes
1answer
24k 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
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
18k 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 ...
6
votes
4answers
8k 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 ...
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 ...
16
votes
3answers
1k views

Is it possible to SSH access a server with a misconfigured subnet?

We have a server where one of our engineers misconfigured the subnet and now we are locked out of this server and the only access that I know of would work is a serial console from IDC (it means ...
15
votes
11answers
73k 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 ...
14
votes
6answers
35k 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.
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 ...
12
votes
4answers
21k 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 ...
12
votes
4answers
24k 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: ...
7
votes
3answers
1k 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?
6
votes
3answers
6k views

Bonding 2 or more Gigabyte NIC together to get 2Gbps performance between 1 server and 1 client?

I have not gotten the server or the NIC yet, but here is the target setup: 1x Server 1x Client 1 or more NIC linked point to point between the Server & Client (No switch involved) So I am ...
6
votes
1answer
4k views

Upgrading from 100BASE-FX to 1000BASE-SX fiber?

I've been trying to upgrade our small fiber network from 100BASE-FX to 1000BASE-SX. The cables are 62.5/125 multimode fibers, all terminated in patch panels with ST plugs (the round ones). As I ...
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
2answers
5k views

ip address scope parameter

In Linux, the command ip address add [...] has a scope argument. The man page says that the scope is "the scope of the area where this address is valid". Follows the list of legal scopes: global ...
4
votes
2answers
10k 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 ...
4
votes
1answer
6k 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 ...
3
votes
1answer
9k views

How can I detect a DDoS attack using pfSense so I can tell my ISP who to block? [duplicate]

Last week my network was hit by a DDoS attack which completely saturated our 100 MBps link to the internet and pretty much shut down all the sites and services we host. I understand (from this ...
3
votes
2answers
1k views

Cheap way to detect client round trip times for http

I am trying to figure out a way to detect round trip times for each IP that connects to port 80 on my server. What is a good way to do this? There are far to many connections, and pinging each ip is ...
3
votes
2answers
1k views

active directory + squid planning for a large network with over than 7000 users

We have about 1600 active nodes and 6000 students in our network and we have a great Cisco backbone, we have 8 faculties (they have sites and wireless access points) and 10 centers like hospital. We ...
3
votes
4answers
8k views

Debian interfaces file - ignore gateway and dns entries from dhcp

In gentoo, this is as simple as: dhcp_ethX="nodns nogateway" How should I go about this in the interfaces file?
2
votes
2answers
5k views

Setting up two NICs on two separate LANs provides error

I wish I had found this before starting in, but it's too late for that... I am running CentOS 5.5. I started following this guide for setting up two NICs on different networks. Everything was ...
0
votes
3answers
3k views

how to completely disable ipv6 on Ubuntu 9.04

what i have done: /etc/modprobe.d/blacklist.conf blacklist net-pf-10 blacklist ipv6 /boot/grub/menu.lst title Ubuntu 9.04, kernel 2.6.28-15-server kernel ...
25
votes
5answers
4k views

Can TCP and UDP packets be split into pieces?

Can TCP packets arrive to receiver by pieces? For example, if I send 20 bytes using TCP protocol, can I be 100% sure that I will receive exactly 20 bytes at once, not 10 bytes then another 10 bytes ...
21
votes
5answers
15k views

How to _MOVE_ files with scp?

How to not copy but move files from one server to another (both Linux)? man scp didn't give me anything useful. I cannot use 'scp' then 'rm' because I must make sure the file is successfully ...
16
votes
3answers
2k views

How does network sniffing software work over a switch?

We have several of standard non-managed 3com switches in a network. I thought switches were supposed to only send packages between peers of a connection. However it appears network sniffing software ...
14
votes
4answers
977 views

Linux Networking - “ip X” instead of ifconfig/route/etc?

I'm used to using commands such as ifconfig, route and so forth on linux to check and change network information. However I know there is an ip command (with various subcommands). I heard somewhere ...
13
votes
3answers
11k 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 ...
12
votes
4answers
13k 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 ...