Managing and using network connectivity on a unix system

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3
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1answer
328 views

how to write a startup dependency on Internet availability?

Some of the services on my Raspberry Pi (~ Debian) depend on the availability of Internet (especially ntpd, for cryptic reasons). Specifically, the availability of a network device or a link being up ...
2
votes
1answer
2k views

iw: what's the default channel bandwidth?

I'm using the iw tool to configure a WiFi interface to sniff the air (monitor mode) on specific channel: ifconfig wlan0 down iw dev wlan0 set channel 1 iwconfig wlan0 mode monitor ifconfig wlan0 up ...
1
vote
1answer
924 views

IP address of a mounted network directory

I have mounted a network directory to /mnt/svr with the following fstab configuration: # <file system> <mount point> <type> <options> <dump> <pass> ...
4
votes
1answer
228 views

How to handle DHCP on two network interfaces, one clobbers the other's /etc/resolv.conf

I have an embedded Debian Linux system. It has two network interfaces, eth0 and ppp0 via a cell modem. The problem I have is that when the system boots up it gets an address via DHCP on eth0. If ...
5
votes
2answers
5k views

Network naming on Arch Linux

I've just installed Arch Linux on my old PC, to do the installation I used wifi-menu wlan0, now I've reboot but if I type: ifconfig wlan0 up I have as a result: wlan0: ERROR while getting ...
9
votes
2answers
3k views

Real-World Use of TCP_DEFER_ACCEPT?

I was perusing the Apache httpd manual online and came across a directive for enabling this. Found a description in the man page for tcp: TCP_DEFER_ACCEPT (since Linux 2.4) Allow a ...
2
votes
1answer
365 views

How do I create an IPv6 overlay network?

I would like to create host-only IPv6 networks on two hosts and then route between them. On each host, there will be a dummy interface, at ipv6_prefix::9. I would like to be able to ping that ...
2
votes
2answers
316 views

Different sites on different interfaces using link aggregation

I read about Ubuntu Bonding and how it allows to bond multiple connections to get several advantages. My requirements is this : I want two different interfaces at a time (A wifi and other Ethernet) ...
3
votes
1answer
5k views

How to handle network interfaces on Crunchbang Linux desktop?

I have installed Crunchbang 10 (Statler) which is based on Debian 6 (Squeeze). By default there is network-manager-gnome 0.8.1 (/usr/bin/nm-applet I believe) running with an icon near the clock/tray ...
1
vote
1answer
242 views

How do I restart the network or ask the system to seek a refresh IP from the DHCP?

I'm running a Minix using VirtualBox. Minix is set to use the DHCP. And the network adapter is using a bridged connection*. When I last saved the state of the machine its IP was 192.168.1.11 ...
3
votes
5answers
216 views

find which system is transmitting through a particular port

I am using command nc -lu <port no.> to find on given port any data is receiving or not. I am getting data if there is transmission going on (but don't know from where!). Is there any way that ...
1
vote
1answer
183 views

How to use one nic for storage traffic & other for network traffic in Linux(Slackware)?

Problem I have a Linux machine (Slackware) with two network interface cards and i want to use one interface for network traffic and other for storage traffic . As this is Slackware i dont know this ...
8
votes
2answers
4k views

escape characters in /etc/network/interfaces

I want to be sure that whatever string I pass into the line wpa-ssid "abc" in /etc/network/interfaces won't be used to break out of the configuration. All I can find in the manual is that \ can be ...
2
votes
1answer
872 views

CentOS 6.5 have to manually add the default route

With CentOS 6.5 on an R710 I have to manually remove the default route; and sleep 10 before adding it back otherwise the interfaces do not use the default route that was added upon boot. There are no ...
1
vote
1answer
680 views

Does an in-kernel firewall sit between the network access layer and Internet layer?

This question is a follow-up to my previous question. Logic for me to says that an in-kernel firewall sits between the network access layer and the Internet layer, because it needs to have access to ...
1
vote
1answer
1k views

Dynamically change /etc/hosts

Each time I change my IP address I have to go edit /etc/hosts and change the line: myPc-Vaio 192.168.1.x I need this change for some programs I am using, so I can't just set the line to 127.0.0.1. ...
3
votes
1answer
273 views

limiting a user's TCP transfer quota

I've been researching how to limit a user's monthly TCP download plus upload quotas. The total transfer limit is 1 TB / month . There are 50 users, so I wish to limit each user to a maximum of 20 GB / ...
0
votes
1answer
260 views

Why won't my computer connect to my Linux access point?

I'm setting up a Raspberry Pi as a proxy access point which accesses the internet via my USB tethered smartphone and is connected to my Windows PC via Ethernet. The internet works fine on the Pi, but ...
1
vote
1answer
63 views

How kernel allows a process to receive network data that do not belong to it? [closed]

Each process is assigned with port number when using network resource. A process can only send and receive network data from its assigned port number. How kernel allows security programs like IDS, ...
3
votes
1answer
132 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 ...
8
votes
3answers
3k views

How does one capture traffic on virtual interfaces?

I would like to capture traffic on Linux virtual interfaces, for debugging purposes. I have been experimenting with veth, tun and dummy interface types; on all three, I am having trouble getting ...
2
votes
0answers
461 views

Rogue AP channel hopping problem

I am able to set AP but despite explicitly setting channel for monitor interface and AP, AP frequency changes regularly. My setup: OS: Kali Linux 1.0 (booted from a USB stick) External network ...
5
votes
2answers
4k views

Determining if a host is online

I'm testing stability of a machine and I need way to simply write a Bash script to determine if a host is online or not. How could I script this? if [ ! $(hostisonline) ]; then # profit fi
1
vote
1answer
248 views

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 ...
0
votes
3answers
182 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. ...
12
votes
1answer
12k 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 ...
0
votes
1answer
189 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 ...
3
votes
1answer
6k 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 ...
0
votes
1answer
4k views

OpenSuse 12.3 keeps renaming network interfaces?

After installing OpenSuse 12.3 (x64) on a server box with a single (onboard) NIC (assigned to eth0), all works fine so far (static IP, static route, no "Network Manager" - just the good old way). ...
0
votes
1answer
294 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 ...
2
votes
1answer
133 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 ...
1
vote
1answer
120 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 ...
0
votes
1answer
934 views

Tacacs over IPv6

I have migrated my Redhat Enterprise linux server 5.5 to IPv6 . Now I want to run tacacs+ for IPv6. When testing from my client, it returns "unable to connect to server for IPv6 address", but for IPv4 ...
1
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0answers
243 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?
6
votes
2answers
31k 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 ...
1
vote
1answer
352 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 ...
0
votes
2answers
290 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.
1
vote
0answers
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 ...
1
vote
1answer
119 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.
0
votes
0answers
370 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' | \ ...
1
vote
1answer
79 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 ...
7
votes
2answers
22k views

Check whether network cable is plugged in without bringing interface up

I am trying to identify NICs on ~20 remote servers (2-6 NICs on every server). To begin with, I want to identify those ready for use and free ones. How can I check the state of the physical media? I ...
1
vote
1answer
114 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 ...
1
vote
0answers
375 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 ...
1
vote
2answers
461 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 ...
1
vote
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. ...
2
votes
1answer
166 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 ...
3
votes
1answer
169 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 ...
0
votes
1answer
119 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 ...
0
votes
1answer
6k views

What is the effect of rsync --block-size on large files?

I want to backup a few terabytes of large files (500mb to 1500mb each) to a backup server (BULK storage) via rsync. For this I use the following command (updated with suggestions from @Gilles): ...