Managing and using network connectivity on a unix system

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9
votes
3answers
14k views

Output traffic on different interfaces based on destination port

My question is basically the same as Only allow certain outbound traffic on certain interfaces. I have two interfaces eth1 (10.0.0.2) and wlan0 (192.168.0.2). My default route is for eth1. Let's say ...
39
votes
4answers
22k views

How does reverse SSH tunneling work?

As I understand this, firewalls (assuming default settings) deny all incoming traffic that has no prior corresponding outgoing traffic. Based on Reversing an ssh connection and SSH Tunneling Made ...
18
votes
4answers
29k views

How to make a machine accessible from the LAN using its hostname

Here are details of the machine I want to access using its hostname: $ hostname hostname $ cat /etc/hosts 127.0.0.1 localhost 127.0.1.1 hostname.company.local hostname It's a default Debian 6 ...
6
votes
3answers
3k views

Can't access select https sites on Linux over PPPoE

My internet connection used to be a direct LAN connection to my provider. Back then, everything would load fine on both Windows and Ubuntu (dual boot). However, a while ago they started needing me to ...
11
votes
4answers
2k views

Block network access of a process?

Is it possible to block the (outgoing) network access of a single process?
7
votes
3answers
6k views

CentOS no network interface after installation in VirtualBox

I have Ubuntu 12.10 on which i installed virtual box on which I setup centos 6.4 i386. On Ubuntu I have: 3.5.0-17-generic kernal running. On virtual box I install centos 6.4 and everything works ...
8
votes
1answer
1k views

Dual network connection

I have a usb cellular modem and a Home LAN connection on my Ubuntu 10.10 box. Both work independently. I want to know how to have both connected at the same time, and be able to specify which ...
13
votes
5answers
11k views

How can I limit the bandwidth used by a process?

I have a CentOS 5.7 server that will be backing up its files nightly. I am concerned that visitors to the various sites that the server hosts will experience degraded performance while the backup is ...
20
votes
4answers
12k views

How to speed up X over SSH on a slow network connection?

Are there any specific recommendations on speeding up X applications over ssh on a slow network connection? In this specific case, I am accessing a server located in west coast from a laptop in east ...
6
votes
4answers
5k views

All commands that should be used to connect to wifi in command line

I would like to switch from gnome to awesome and I would like to connect my wifi network in command line (instead of using gnome tools). So, I searched on the internet and found approximatively the ...
2
votes
1answer
5k views

Set Static IP in CentOS 6.4?

Most guides seem to revolve around modifying ifcfg-eth0, which doesn't exist on my system.. [root@Azaz07]# vi /etc/sysconfig/network-scripts/ifcfg-eth0 [root@Azaz07]# ls ...
2
votes
1answer
9k views

Two interfaces, two addresses, two gateways?

I have a system that has two network interfaces with different IP adresses, both of which are in the public address range (albeit via NAT in the case of the first one) and both of which have different ...
6
votes
1answer
91 views

Why my ethernet interface is called enp0s10 instead of eth0?

Just that, when I run ifconfig -a I only get lo and enp0s10 interfaces, not the classical eth0 What does enp0s10 means? Why is there no eth0?
3
votes
1answer
592 views

Route SSH to host through interface

Is it possible to route all outgoing requests for SSH (port 22) to mydynamicdns.afraid.org via wlan0 instead of eth0 when both are connected? Since my IP is dynamic, I would like to use a name ...
2
votes
1answer
2k views

How To Diagnose Faulty (onboard) Network Adapter

I'm looking for advice on diagnosing ethernet connectivity issues under Linux. I suspect it's a hardware issue, though I am not entirely sure. It's an nVidia chipset and ethernet adapter. The device ...
9
votes
3answers
7k views

Linux network troubleshooting and debugging

From time to time Linux and Unix users faced with various network problems. Many of these problems are presented here and at some others troubleshooting forums, but the are very concrete and contains ...
9
votes
3answers
8k views

Only allow certain outbound traffic on certain interfaces

I have rather an odd issue. I have a server with two network interfaces eth0 and eth1. Each are connected to a different network. Each network has a internet gateway. The server has various outbound ...
16
votes
2answers
1k views

Is there an easy way to programmatically extract IP address?

Is there an easy way to programmatically extract IP address, without tedious parsing of ifconfig? I would not mind simple command output processing using sed to do it but not processing multiline ...
15
votes
6answers
10k views

How to get my own IP address and save it to a variable in a shell script?

How can I get my own IP address and save it to a variable in a shell script?
13
votes
3answers
8k views

How to find what other machines are connected to the local network

How can I see a list of all machines that are available on the LAN I'm am part of.
14
votes
9answers
789 views

Simple file transfer

Given two Linux boxes on a LAN, what's the simplest way to transfer files between them?
4
votes
3answers
3k views

Send duplicate packets over two Internet connections

I need to duplicate an RTP stream over two different (non-reliable) Internet connections. On the receiver side, I will probably run a custom program that will use a buffer and rebuild the stream ...
6
votes
2answers
627 views

Share keyboard over network as separate device?

I am trying to achieve something similar to this: http://superuser.com/questions/67659/linux-share-keyboard-over-network The difference is that I need the remote keyboard to be usable separate from ...
6
votes
1answer
4k views

What is the loopback interface

What is the loopback interface and how does it differ from the eth0 interface? And why do I need to use it when mounting an ISO or running a service on localhost?
5
votes
1answer
4k views

How to diagnose a reliably unreliable connection?

Where I'm living now, the internet connection (wired) shows the following weird symptoms. They seem to be independent of whether I use host names or IP addresses. Pinging works Skype works Wget ...
7
votes
2answers
230 views

Strange temporary network outage in Linux

I'm facing a very annoying problem that I noticed a week from now and for which I can't find an answer: my network suddenly stops responding, usually coming back exactly 25 seconds later. I was using ...
3
votes
2answers
3k views

How to connect two computers via internet with ssh?

I want to connect another computer via internet that doesn't have a public IP. Is there any away to do this?
3
votes
3answers
1k views

How to get list of computers similar to what is shown under “Network” in Windows

In Windows 7 when I click on Network I get a list of computers with the same workgroup of mine. But in Fedora when I click on Network I just get a single item Windows Network and I can't see the ...
3
votes
1answer
235 views

Set up network to share a printer connected to one particular machine on the network

How do I set up my Ubuntu machine to allow other computers to print to it? The set up is: All computers are connected to the network 1 dual Ubuntu/Windows 7 netbook 1 multibooting ...
1
vote
2answers
1k views

How can I Forward a subDomain to a specific port?

My apologies if this has been asked before. I haven't found an adequate solution so... yeah. When a specific domain, "example.com" is accessed, I want it to act normally. In other words, it should go ...
8
votes
5answers
8k views

Why does SCP hang on copying files larger than 1405 bytes?

I'm trying to copy a file from one of my local machines to a remote machine. Copying a file with size upto 1405 bytes works fine. When I try to scp a larger file, the file gets copied but the scp ...
3
votes
1answer
81 views

How security programs like firewall, IPS and IDS have access to network data?

It is said that kernel responsible for the transport, internet and network access layers for a network data. Then, the network data is passed on the appropriate process based on port number. How ...
3
votes
2answers
2k views

Bridge not working

We want to create bridge (mybridge) on our board over eth0 and eth1 interface. The board runs Linux 2.6.34.9. Following are the commands: brctl addbr mybridge ifconfig eth1 0.0.0.0 ifconfig eth0 ...
3
votes
3answers
7k views

Find out network traffic per IP

We have one central server which functions as an internet gateway. This server is connected to the internet, and using iptables we forward traffic and share the internet connection among all computers ...
3
votes
5answers
769 views

How can I test whether connection to the given host/port is established in Bash?

Currently I'm using netstat for this: if netstat -an | grep ESTABLISHED | grep $address:$port > /dev/null; then # command fi Is there a more elegant solution?
3
votes
2answers
7k views

Firmware for wireless card on Ubuntu/Debian?

This is a follow up to my previous question about Debian support for Linksys Wusb600n. I have tried running the Ubunut/Xubuntu LiveCDs and the WiFi does not come up. The Gnome Network Manager menu ...
3
votes
2answers
2k views

Setup WLAN interface on Debian

I am trying to configure wlan on my dockstar. I installed wireless-tools, zd1211-firmware and wpasupplicant. My /etc/network/interfaces file looks like this: auto lo eth0 iface lo inet loopback ...
3
votes
1answer
842 views

Under Ubuntu, how do I set a static IP for firewire?

I am using Ubuntu 10.10 on my laptop, which connects to our network wirelessly. Since it sits on my desk next to my desktop, I have a private network between the two using a firewire cable, because ...
2
votes
1answer
1k views

No wired ethernet connection

I'm using elementary OS (based on Ubuntu 12.04) and yesterday I woke up to no wired ethernet connection. As far as I can remember I changed absolutely nothing, it was working at night and not anymore ...
1
vote
0answers
67 views

No network interface for the lan9118 emulated on QEMU 1.4.0 overo machine

Im using QEMU 1.4.0 Ubuntu 13.04 distribution. Im trying to make the virtrual machine part of the host network so Im ussing this command: sudo qemu-system-arm -M overo -m 1024 -sd ./test.img -clock ...
36
votes
2answers
4k views

How does SSH connection survive a network restart?

From a Linux SSH shell, type /etc/init.d/network restart to restart the network service. I expect my SSH connection to die since the network service goes down. But it doesn't. Very cool. But how does ...
14
votes
5answers
9k views

Sending audio through network

This is a rather crazy idea. I am planing to set up a configuration that would send audio being played on my laptop to my home server via local network so that the sound is played on the server ...
9
votes
2answers
39k views

Orphaned connections in CLOSE_WAIT state

I've got a SLES machine that accumulates TCP connections in a CLOSE_WAIT state for what appears to be forever. These descriptors eventually suck up all available memory. At the moment, I've got 3037 ...
13
votes
7answers
8k views

Faster way than ping for checking if computer online?

I'm writing a wake on lan script for a set of our lab computers. We have sqlite db with a list of the computer hostnames, IPs, and MACs and currently I ping each of them with '-c1' so it doesn't run ...
12
votes
3answers
1k views

Can I limit a user (and their apps) to one network interface?

As the title really. I've actually got two scenarios to apply this: Multiseat Desktop: two network connections both with internet gateways and two accounts doing bandwidth-intensive tasks on each. I ...
17
votes
1answer
8k views

Why are the first 1024 ports restricted to the root user only?

This is more idle curiosity than anything else. A friend of mine asked me 'which port range is it that only root can use under Linux?' I told him 0-1024 were restricted. Then he asked my why it was so ...
4
votes
1answer
4k views

CentOS doesn't know what the internet is

So I've done my share of investigating this problem... I just recently created a CentOS 6 VM on my LinuxMint box using VirtualBox. I left all the recommended values the same upon creation (8GB HDD, ...
5
votes
2answers
2k views

Routing for multiple uplinks/providers

I have a PC with two internet connections. The first one is an Ethernet interface to connect to my local network and access internet via my router. The second one use a GSM modem to connect with ppp. ...
4
votes
2answers
2k views

How to know if a network interface is tap, tun, bridge or physical?

As far as i know, there are 4 main types of network interfaces in linux: tun, tap, bridge and physical. When i'm doing sys admin on machines running KVM, i usually come accross tap, bridge and ...
4
votes
2answers
18k views

Bring down and delete bridge interface that's up

How do I remove a bridge that has an IP address that was brought up manually and isn't in /etc/network/interfaces? $ ifconfig br100 br100 Link ...