Managing and using network connectivity on a unix system

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3
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3answers
190 views

How do you prevent a DHCP release during shutdown?

I am currently using Ubuntu 14.04, but expect this to be applicable for different distros. I would like to prevent a DHCP release during shutdown, and opt for either the lease to expire or for a DHCP ...
0
votes
0answers
27 views

ssh_exchange_identification: read: Connection reset by peer (Have access to the server)

I'm getting "ssh_exchange_identification: read: Connection reset by peer" for ssh into a machine. However, it only happens to my machine and it works for the other person next to me (we share the same ...
0
votes
0answers
29 views

command line tool group chat utility under linux

I am working on mac osx Yosemite. I want to reach to a user under a certain IP address. (It might be local network or thru internet). I want to do it thru terminal using the default tools that ...
3
votes
0answers
27 views

Is there a thing like “veth”, but without link-level headers?

When I use separate network namespace, I often set up networking there using veth: ip link add type veth ip link set veth0 netns 1 ifconfig veth1 192.168.60.2 ip route add default via 192.168.60.1 ...
15
votes
6answers
5k views

What is using this network socket?

I'm trying to use NTP to update the time on my machine. However, it gives me an error: host # ntpdate ntp1.example.org 10 Aug 12:38:50 ntpdate[7696]: the NTP socket is in use, exiting What does the ...
2
votes
0answers
350 views

What does `NO-CARRIER` and `DOWN` mean for a wireless interface?

I have a remote server and I log output of certain commands while the server cannot access the internet. It uses a wireless interface to connect to the internet. In a working state the output of ...
4
votes
3answers
5k views

Configure multiple interfaces with different hostnames using DHCP and DNS

I have a machine running Ubuntu 12.04 Server with two interfaces connected (eth0, eth1) to the network. Our network is set up so that a FreeBSD based DHCP server hands out leases and registers the ...
1
vote
1answer
50 views

CentOS 6 Static IP Address

I've just assigned my CentOS machine with a static IP address using the /etc/sysconfig/network-scripts/ifcfg-eth0 which has the following lines and seems to be working #eth0 config DEVICE="eth0" ...
0
votes
1answer
137 views

Laptop connected to wifi but no internet

For some reason my wifi has decided to stop working. I can connect to APs, I can have excellent signal strength, but I can't actually load any web pages or ping anything. I know it's my laptop because ...
19
votes
5answers
4k views

What is a socket?

Could someone explain to me what a socket is? I see it in many acronyms in context of SSL, etc. Also, why is it called a socket? Is it purely because it was what a name they invented? Or was it the ...
0
votes
1answer
19 views

How to effectively capture traffic on port 5060 between specific time internals?

users. I want to capture traffic on port 5060 for one week in a file, than wants wireshark to rotate file and start capturing for next week with a different file name. I know little about tshark, ...
1
vote
1answer
31 views

Can't use 2 interfaces at the same time

I can't get eth0 and usb0 (same with wlan0) working at the same. When I activated the Android Tethering, I did route add default gw 192.168.42.129 usb0, and so, route -n outputs: Table de routage IP ...
1
vote
0answers
2k views

Understand the Route table

I just setup the OpenVPN and it is working as expected. However, the routing table of the client is confusing me to no end. Here is the route table: # route -n Kernel IP routing table Destination ...
15
votes
6answers
45k views

How to change the order of the network cards (eth1 <-> eth0) on linux

Is there any way to swap network interfaces (eth1 <-> eth0) after system installation. My brand new Debian 6.0 install assigned PCI network card as "eth0" and motherboards integrated network ...
1
vote
1answer
71 views

How to create permanent ip alias belonging to different subnets in Centos

I followed this link and created few alias ips on my centos 6.5 machine but all these ips belong to same subnet. What I have: My machine: eth0, 10.91.56.3 IP Alias1:eth0:1, 10.91.56.4 IP ...
0
votes
1answer
34 views

Is there a way to switch interface only by interface name?

I am currently working on how to switch network interface in Linux environment. And i am experimenting on switching network interface by switching default gateway, for example switch to wlan0 when ...
2
votes
1answer
41 views

On a router, what decides if a packet should be forwarded or directed into the router itself?

I'm trying to learn how packet routing works on a linux-based router (OpenWRT in my case) a bit better for setting up a few projects/just-learning. Referencing the below chart, I'll break this into ...
0
votes
0answers
55 views

Creating an open wifi acess point for April Fool's Day which I want the client can only visit the login/splash page, but not working

I bought a Hiwifi J2 (Chinese) router, and sysupgraded to OpenWrt (not official version, but a patched version based on OpenWrt Barrier Breaker: https://github.com/rssnsj/openwrt-hc5761). Then ...
1
vote
0answers
29 views

No “rwnd” option to “ip route” for managing the receive window?

Context: I'm doing some self-guided studying on TCP Window shaping. The scenario I'm trying to control for are clients which will be pulling down large amounts of data in addition to their normal ...
1
vote
0answers
69 views

/opt partition not mounting in DD-WRT v24-sp2

I'm facing problems trying to install optware packages on a TP-Link TL-WR841n v8 running DD-WRT v24-sp2 (4MB flash, 32MB RAM). I did the following through telnet: nvram set jffs_mounted=1 nvram set ...
1
vote
3answers
69 views

how to automate creating firewall rules?

There is a complex live system - few vlans. In each of them there are linux servers, and on every server there are services. Services connect together - for example service http on host A connect to ...
0
votes
1answer
45 views

Apple Home Sharing on a Linux machine

Is it possible to share a directory with media files to an Apple TV (Gen 2 & 3) using Home Sharing on a Linux machine? I've found some solutions suggesting DAAP but none of them seems to be for ...
2
votes
2answers
63 views

Is it possible to have multiple virtual machines with the same (guest) ip on the same host?

What I try to achieve: Multiple virtual machines (virtualbox) on a Debian host which communicate with another server (not with each other or the host). All VMs need to have the same static network ...
2
votes
1answer
44 views

Why does scp not show true upload speed?

Every time I'm trying to upload a file using scp on my slow upload connection (~100kb/s), it shows something like : test 27% 2208KB 2.2MB/s 00:02 ETA On the first ...
2
votes
1answer
975 views

ping receives no packets, but tcpdump can see them coming in

I'm migrating an old Ubuntu OpenVZ instance (Jaunty) to a new CentOS 6.3 host (using vzdump/vzrestore). Now networking does not work properly. Facts: It works just fine if a setup a new OpenVZ ...
1
vote
2answers
87 views

How to tar, split, pipe, untar over ssh

I'm copying large files over LAN, and I've noticed that with doing one ssh pipe, I can get around 10MB/s transfer speed. However, if I shoot off four of those at the same time, I get around 40MB/s ...
1
vote
1answer
162 views

Can't access my apache server from outside LAN (Raspberry Pi)

I know this question was asked a lot, but unfortunately none of the posts really helped.. I'm trying to set up an Apache server on my Raspberry Pi. I managed to set it up correctly I think, but I ...
0
votes
0answers
36 views

How do you create an ip alias using iproute utils?

While reading the O'Reilley book on Apache Web Server, they gave an example on using ifconfig to set ip aliases on an interface: ifconfig ep0 192.168.123.2 ifconfig ep0 192.168.123.3 alias netmask ...
1
vote
1answer
43 views

What is a hotplug event from the interface?

According to Debian Network setup document allow-hotplug <interface_name> stanza in /etc/network/interfaces file starts an interface when the kernel detects a hotplug event from the interface. ...
11
votes
1answer
13k views

Good detailed explanation of /etc/network/interfaces syntax?

I understood the very basic concept of how to use /etc/network/interfaces, but all I find online are examples, example after example, which I can copy-paste from. What I miss is an explanation of the ...
2
votes
3answers
72 views

One-liner for getting an IP address of an internal DNS name?

I have an internal DNS name for which I'd like to get the IP address. Is there a nice Bash one-liner I can issue to convert internalip1.mydomain.com into 10.10.10.10?
0
votes
1answer
31 views

Connect through different interfaces to the same server

i have two pppoe interfaces - ppp0 and ppp1. I would like to reach the same server on both interface. I added the desired ip address to the route table: route add 10.88.40.13 ppp0 And I could ...
19
votes
7answers
19k 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?
6
votes
2answers
3k 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-- ...
2
votes
2answers
38 views

mknfsmnt fails with “System call error number -1”

This system is part of a cluster and the other node mounts the nfs share successfully. This is currently the active node which means it has a secondary service ip address. I think this is related to ...
0
votes
0answers
62 views

How can I configure multiple tap interfaces for a single KVM virtual machine

I am trying to setup a VM using Linux KVM for a F5 BIG-IP VE deployment (used in a lab) ...
2
votes
1answer
43 views

make my Debian laptop switch autoamtically to a backup connection

I have a laptop with Debian OS installed under it. It is initially connected to the internet using an Ethernet cable (via a modem) and I want to automatically switch to a backup wifi connection (which ...
1
vote
1answer
28 views

I need dhclient to flush IP address/routes when link goes down

I am running one Ubuntu Server 14.04 with network configuration using /etc/network/interfaces and so ifup/ifdown scripts. I realised that if I configure one interface in DHCP mode, then I unplug the ...
1
vote
0answers
17 views

Transport keyboard/mouse events to a keyboard/mouse-less remote host

I want to send keyboard and mouse events from a small ARMv7 computer board to a remote one, which has no keyboard nor mouse. I'm planning to send these events on a locally implemented CAN bus. The ...
1
vote
1answer
45 views

How do I run a program without network access? [duplicate]

I am making a program that scrapes information from some web services. I want to test how my program reacts when it can't reach the web service, like if the web service is down or if the local ...
0
votes
0answers
25 views

how do I disable the firewall through YaST?

The fine manual states: The Start-Up section defines how your firewall will start. You can either have the firewall start automatically when booting (recommended), or you can set the firewall ...
4
votes
1answer
121 views

what is “rfc3442-classless-static-routes” in /etc/dhcp/dhclient.conf

I am trying to debug DHCP on my laptop (I am using dhcping and dhcdump to see what the DHCP server sends back). Following is my /etc/dhcp/dhclient.conf. option rfc3442-classless-static-routes code ...
3
votes
5answers
9k views

Cannot delete bridge - “bridge br0 is still up; can't delete it”

I have the same problem as this guy : Bring down and delete bridge interface that's up But that solution does not work for me. I remove all interfaces from the bridge using brctl delif . I then ...
0
votes
0answers
89 views

can't connect to remote host with MySQL…firewall problem?

I've granted privileges to thufir for remote access through the shell (correct?), but cannot seem to actually connect. The router firewall has SPI to off. I've disable the IPv6 firewall on the ...
2
votes
2answers
99 views

How to print from a given range of ip addresses every class-c with the last octect replaced by an asterisk

example: I have a range from 10.0.100.0 to 10.0.224.0 and I want the output like this: 10.0.100.* 10.0.101.* 10.0.102.* and so on
0
votes
1answer
49 views

WiFi only connects to my router, not to any other access point

I have a Raspberry Pi 2 with a WiFi USB dongle. I don't know the brand or model, I got it for free with my Xtreamer Mk1 in 2009. My Windows 7 PC installs some generic Realtek RTL8191SU WLAN adapter ...
0
votes
0answers
38 views

eth0/usb0 bridge breaks after removal and replacing android phone

I'd like some help with a networking bridge issue I've run into. I'm trying to make a bridge with eth0 and usb0 (my android phone). After running the brctl commands the bridge works wonderfully. But ...
1
vote
1answer
62 views

Test for open TCP port in bash script

I want to delay the script execution until a certain server process is ready, which it is once it accepts incoming TCP connections. How do I test if a local TCP port is open (I get a SYN/ACK answer)? ...
4
votes
2answers
418 views

Using bash's `/dev/udp`, how would I know if the port was open?

I do not have access to netcat or nmap so I'm trying to use bash and the /dev/udp/ special files to test ports. I could do something like: echo "" > /dev/udp/example.com/8000 But $? is always 0 ...
1
vote
1answer
2k views

How can I disable IPv6 in custom built embedded setup

I have an embedded system built using buildroot. I have had a number of network issues, one of which is that my machine cannot see its gateway despite it being on the same subnet. I have tried using ...