Managing and using network connectivity on a unix system

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tcp/ip - trigger action or event after period of no network activity on certain port(s)

Is it possible, perhaps using iptables or one of the wrappers/frontends to iptables, to trigger an action or run a script after a certain period of time has elapsed with no network activity on a ...
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1answer
3k views

Set up network with static IP and wpa_supplicant on Debian

On Debian, I am trying to set up my network to use ad-hoc mode with a static IP address. I also want wpa_supplicant to be running so that I can scan use it to scan for WiFi networks in range. To get ...
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1answer
13k views

Why is my TCP throughput much greater than UDP throughput?

I haven't done anything unusual to my hardware or kernel configurations (all default settings, fresh OS install, Linux kernel 3.11 TCP/IP stack) and I'm averaging about 3.83 million messages per ...
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3answers
12k views

Multicast UDP not working

Multicast UDP on raspberry pi I haven't narrowed things down enough to know if my issue is because of debian, raspbian specifically, or if I am just missing a something completely. I have a python ...
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1answer
191 views

External IP check reports different IP from /etc/network/interfaces

My ISP gave me static ip range for internet access: 123.123.123.120-125 (Debian) /etc/network/interfaces: auto eth1 iface eth1 inet static address 123.123.123.120 netmask 255.255.255.0 gateway 123....
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1answer
4k views

tftp transfer painfully slow

I am using HPA's tftp server for PXE boot. When I try downloading an image from my tftp server using curl, the transfer rate is less than 3 MB/s, even on my 1Gb network. curl -o initrd.gz tftp://192....
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2answers
738 views

Send traffic to self over physical network on Ubuntu

I have a dual port ethernet NIC and let's say I have connected both ports in a loop and assigned the following IPs to the 2 ethernet interfaces: eth2 -> 192.168.2.1 eth3 -> 192.168.3.1 I want to ...
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188 views

iptables rules - input and output

I'm new with Linux and iptables. I have a Ubuntu Server distro (12.04) on a PC which has 2 network interfaces (eth0 and eth1). I also have 2 laptops, one is plugged to eth0 and the other to eth1. ...
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304 views

Unidentified network connections

I have an external-facing ftp/webserver (with virtual hosts) running Ubuntu 12.04LTS, and I have some concerns about some network traffic I'm seeing. Some background. I tried to be as preventive in ...
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1answer
7k views

How to use netperf on specific NIC port?

I have two servers, SERVER and CLIENT. Each server has its own onboard 1 GbE ports, and its own NIC with a 10 GbE port. SERVER and CLIENT are interconnected on both a 1 GbE switch (administrative ...
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128 views

What do the colours in iptstate mean?

I'm running iptstate to try and resolve a VPN issue through my router, and some of the traffic is highlighted in green and some is highlighted in red as I move the cursor up and down the list. I don'...
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138 views

Are application layer protocols part of library routines?

Where do application layer protocols reside? Are they part of library routines of language e.g. C, C++, Java? As goldilocks says in his answer, this is about the implementation of application layer ...
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250 views

Which filter configuration in kernel rate limit the outgoing packets to 1packet/sec?

Which net filter in kernel configuration other than iptables enable rate limiting on the outgoing packets on ethernet port?
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35k views

check if interface eth0 is up (configured)

I need to check with a script, whether eth0 is configured. If so, the script will do nothing. Otherwise it will start wlan0. (I don't want both eth0 and wlan0 to be up at the same time). What would ...
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1answer
364 views

Why aren't my iptables rules appearing in the relevant list after reboot?

I am trying to write two persistent NAT rules, which I save via iptables-save > /etc/iptables.ipv4.nat, and restore upon reboot via pre-up iptables-restore < /etc/iptables.ipv4.nat in my /etc/...
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81 views

Can slattach control a serial WiFi device?

I have a Wi-Fi device which is driven by AT commands over a USB-Serial connection. I am able to successfully make a serial connection to the device and set the SSID, PSK, obtain an IP address, and do ...
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2answers
318 views

how to get the return value of wpa_supplicant?

My question is really simple I want to get the return value of the command wpa_supplicant, when connected to the internet, to know that I am connected or not with a shell script.
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17k views

nc: bind failed: Address already in use

I am trying to execute nc command from a script , my script is executing nc command on different ports of Destination using the same source port. e.g: nc -p 8140 -z -v -n 10.X.X.9 9090 nc -p 8140 -z ...
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125 views

Can I mirror lo as eth0? [closed]

Is it possible to make eth0 point to lo? I have dumb process that keeps acting as eth0 exists while it doesn't.
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391 views

AiX topas snapshot to web

My script for taking snapshot from TOPAS looks like this: #!/usr/bin/bash whoami export TERM="xterm" (sleep 3; echo q)| topas -Emi 2 | \ tr -d '\r' | \ ...
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4answers
28k views

Arch Linux not connecting to Wifi anymore

I have been using Arch Linux over a month now. I have used wifi-menu to connect to my Wifi Network. I run the command every time I start my laptop. wifi-menu always gives this error when I try to ...
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1answer
82 views

How can I translate these OpenVPN client configuration instructions to work with Fedora 20?

Here's the link to the full instructions. When I get to step 9, under the heading "9. Setup Client Config Files", it says: Now we will configure the openVPN to work as client. Remember that we ...
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1answer
120 views

Wait until no incoming network connection for N minutes, then execute a command

I want to put my Debian Wheezy home server to sleep, if it wasn't accessed through the network for a certain amount of time. I thought of a bash script that uses netstat to count the number of ...
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403 views

udhcpc starting before PHY is up

I'm having a issue with my Ethernet PHY not being up before eth0 tries to get an IP address This is my etc/network/interfaces # Configure Loopback auto lo iface lo inet loopback # The primary ...
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1answer
149 views

How can I know if a network is password-protected before connecting to it?

What command can I run to determine the security of a wireless network, without needing to connect to it? I want to know if it needs a password to connect or if it's a public network without security. ...
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2answers
501 views

What could cause a ping request to return inconsistently timed results

Here is a sample run: 64 bytes from 192.168.1.9: icmp_seq=27 ttl=64 time=8852.917 ms 64 bytes from 192.168.1.9: icmp_seq=28 ttl=64 time=7918.074 ms 64 bytes from 192.168.1.9: icmp_seq=29 ttl=64 time=...
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1answer
170 views

How to make HA Heartbeat failover when either of two NICs connection is lost?

I was successful in configuring a simple Heartbeat setup on Ubuntu 12.04, which will fail-over two VIPs to a second server when BOTH Ethernet links fail. What I can't figure out is how to fail-over ...
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1answer
509 views

Linux: How to auto-configure IP routing based upon ping results

I've got a linux server with two possible connections to the net: one is a slow, high-latency cellular modem (ppp0), and the other is through fast wifi->broadband (wlan0). The problem is that the ...
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1answer
173 views

Letting an OVZ container use the hosts ip

I have a server over at OVH and it has Proxmox installed on it. I've created a container but I want to host a server in there and I want it to use the host's external IP. How can I do this? I hope I ...
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1answer
129 views

alternatives to adding entry in /etc/hosts [duplicate]

I would like to access a remote host using a short name. On a system where I have admin rights, I would achieve this by adding an entry in /etc/hosts file, something like this 121.121.122.1 ...
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143 views

Did this tutorial block pings to my server?

I am a programmer teaching myself linux admin stuff. I followed this tutorial to setup a firewall on a VPS. As a part of that tutorial, I block all traffic except for web traffic and SSH traffic. I ...
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98 views

Will this open up a non-standard port to ssh?

I am following tutorials on iptable and want to allow ssh traffic on my non-standard SSH port = YYY. I think this is how you do it, but want to double check so I don't lock myself out of my server. ...
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252 views

What does the last column in this IP table mean?

I ran the following commands I found in a tutorial: $sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT $ sudo iptables -L and got target prot opt source ...
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3answers
3k views

Check that fail2ban is running?

I just installed and configured fail2ban. I want to make sure it is working. I don't want to block myself from the server so I can't just login (poorly) a bunch of times. How do I see that fail2ban is ...
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2answers
1k views

change eth0 to eth1 without udev

I have a very interesting issue. We have Redhat 4 Linux and it is has 4 ethernet interfaces: eth0 eth1 eth2 eth3 Now, only eth0 is connected to LAN and everything is working fine. We have special ...
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830 views

What is the default action for incoming packets that don't match explicit iptables rules?

CentOS 5.x I'd like to understand what is specifically happening to incoming packets that don't explicitly match rules in my iptables chains. Is the default action to reject them? Or drop them? How/...
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88 views

How might I log my Internet traffic, grouped by IP address/hostname, port, etc?

While I'm going to be switching to a slightly saner plan soon, being stuck on a 5GB monthly bandwidth cap has made me very data-conscious, and I'm looking for a way to log my Internet usage in such a ...
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2k views

How do you set a vlan priority on a nic in freeBSD?

This question could arguably be posted on both networking.stackexchange and unix.stackexchange. I'll start here. I have a freeBSD (pfsense 2.1) server running as a router on google fiber. In order ...
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201 views

Bridging two interfaces for intranet only

We have two ALT linux servers with real IPs. They both are in intranet via commutator. Each of them also has an additional LAN network interface. We want to connect these servers to each other ...
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2answers
306 views

How to listen to a specific port and return 200 status

How can I listen on my server on specific port and just return HTTP 200 status if someone tries to connect ? Can nc be used to return HTTP status ?
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1answer
1k views

How to check what `wondershaper` has done?

I used this command: sudo wondershaper eth1 20 20 to limit network traffic. The command shows no errors. But I need a command or network monitor or gui which confirms this limitation. For example, ...
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34k views

hostapd will not start via “service” — but will start directly

I am having trouble getting hostapd to start as a service. It fails when I try to start it: $ sudo service hostapd start [FAIL] Starting advanced IEEE 802.11 management: hostapd failed! From what ...
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2answers
8k views

Cannot connect to any localhost connections

I'am using Centos 6.5 with latest updates. My problem is that whenever i try to connect to some local service it just hangs for example: wget wget 127.0.0.1 --2014-03-11 12:43:42-- http://127.0.0....
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1answer
491 views

tcpdump command works only on local ip

I am trying to capture some IP packets in my personal LAN with tcpdump, through the command tcpdump -A -i eth0 'tcp and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0) ...
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2answers
3k views

Why doesn't stopping the nginx server kill the processes associated with it?

When I stop nginx like this on ubuntu 12.04, I get the following errors: $ sudo service nginx stop Stopping nginx: nginx. $sudo service nginx start Starting nginx: nginx: [emerg] bind() to 0.0.0.0:80 ...
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808 views

SSH to Linux Container from Other Machine

I am trying to learn about Linux Containers and this is my first encounter with servers, ssh and many other things that I do not know the terms yet. I create five different containers and authorized ...
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1answer
600 views

How can I access networked filesystems that I've mounted in Nautilus?

I've mounted a networked filesystem in GNOME by clicking on the icon in the left of Nautilus. However, when I use the terminal, I can't figure out how to access that filesystem. Is it possible?
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Wireless bridged networking in KVM. Why is it so complicated?

I've been using VirtualBox (and sometimes VMWare) for years and I've never had any problem with the virtual network adapters, no matter if the physical ones were wired or not. I also played some time ...
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2answers
10k 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 ...
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1answer
194 views

Network connectivity problem - Debian 6 server

I'm having a problem with a Debian 6 server where it looses network connectivity and doesn't come back (server does not respond to pings, and can't connect to any services). The problem happens ...