Linux Networking refers to any networking function performed by a server running Linux. A Linux server operating as a router or firewall are the most common applications.

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Debian iptables load fail

I Have Debian 8 Jessie and I have installed iptables, but it's not correctly. I can add rule just like: iptables -A OUTPUT -s 212.50.128.0/19 -j DROP but it's not working. Iptables -L command work ...
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1answer
21 views

Disable eth0 on boot, but allow to turn back on

We are setting up an offline/offsite backup server. The purpose is to have it offline and uncontactable from anything. Then, once the cron starts the backup process it will enable the network, backup ...
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4answers
50 views

How do I find out linux gateway IP address?

I have CentOS 6.7 with two Internet connections eth0 - dynamic IP address and dynamic gateway via DHCP (controlled by NetworkManager) ppp0 - dynamic IP address and dynamic gateway (configured with ...
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9 views

Hostapd connected but without an internet connection

I am able to connect my Android device to my Linux Mint Server, however, I can only browse my server's websites and not those over the internet. My server has internet access via eth0 without any ...
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2answers
46 views

why Ethernet MTU size is 1500? [on hold]

Can somebody explain that why the Ethernet Maximum Transmission Unit was chosen to be 1500 bytes (why exactly 1500) ? It might have some historical reason.
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2answers
32k views

“Stale NFS file handle” after reboot

On the server node, it is possible to access an exported folder. However, after reboots (both server and client), the folder is no longer accessible from the clients. On server # ls /data Folder1 ...
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1answer
18 views

Setting default gateway on CentOS 7 and showing it using route and netstat -r

I am following a tutorial found here on how to setup a gateway for each adapter and also a default gateway: http://linux-training.be/sysadmin/ch22.html But when I run the commands $ route and $ ...
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1answer
7 views

Iperf3 keeps hanging when running UDP test

I wrote a Python program that runs iperf3 in a for loop with different datagram sizes. I am using Python's subprocess.call function to run iperf3 like this: iperf3 -u -c 185.82.21.60 -b 100M -t 5 -l ...
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9 views

How to ensure via shorewall that the network is closed at boot time?

I use Shorewall (on Ubuntu 16.04) and would like to ensure that between the start of the boot process and the moment iptables rules are applied the network is in a closed state. There provision for ...
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2answers
3k views

WMI: wmic linux agent query error: NTSTATUS: NT_STATUS_ACCESS_DENIED

Myself new to wmic and keep trying for a long time with default agent query approach. wmic is linux based WMI tool to talk to windows WMI agent. While trying to fetch data with wmic from nt(win7 with ...
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1answer
89 views

no network in nspawn container

I'm having an issue with networking in a systemd nspawn container. I have enabled the -n / --network-veth option in the systemd-nspawn command. This has worked a few hours ago (I know that because I ...
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1answer
2k views

Adding subnet to a vsphere with single vcenter and esxi host

Let me start of by saying that I do not specialize in networking, I am in the process of adding additional VMs to a testing environment and wanted some recommendations. In this case I am running a ...
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1answer
22 views

How to redirect traffic through IPv6 IPSec (strongswan) gateway?

I'm trying to set up IPSec secured connection to the gateway. Have three hosts: A: eth1 - fec0:1::1/64 B: eth1 - fec0:1::2/64 eth2 - fec0:2::2/64 which is gateway between A and C; forwarding is set ...
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0answers
14 views

all outgoing tcp packets have source port 0.0.0.0 [on hold]

currently i am connected to a network 169.254.x.x (a Hostel's Network) and there are three gateways. 169.254.10.1 169.254.20.1 169.254.30.1 above three works as dhcp servers as well. from a windows ...
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5answers
10k views

Override DHCP hostname on RHEL5/CentOS/Amazon Linux

I'm running Amazon Linux (based on RHEL5) on EC2. I have my own domain name pointing to the instance's elastic IP. Amazon auto-assigns the instance a generic (and not visible on the Internet) ...
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3answers
11k views

e1000e Reset adapter unexpectedly / Detected Hardware Unit Hang

I have a Dell 1U Server with Intel(R) Xeon(R) CPU L5420 @ 2.50GHz, 8 cores running Ubuntu Server Kernel Version 3.13.0-32-generic on x86_64. It has dual 1000baseT networking cards. I have it set up to ...
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1answer
14 views

ksoftirqd/0 hit ~100% cpu usage led network lag

I run an app on CentOS6(e5-2667v2 x2 with 128GB RAM, 1000M network interface), When network load up to ~300Mbit/s, the ksoftirqd/0 process hit ~100% cpu usage, and begin loss packet. How can I do?
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switch not giving desired dhcp leases [closed]

Our college has one router. a switch at each hostel floor. now if this router is disconnected from the switch then switch assigns IP addresses in the range of 192.168.x.x but if the router is ...
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Dlink dir 620 strange behaviour [closed]

I have replaced Dlink dir 300 with Dlink dir 620. In dir 300 I had the enabled config of port forwarding to the local raspbery pi, on port 80, and had connected internet domain name. Now I haven't ...
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1answer
37 views

Running LAN services on a router/firewall

So I work in a company where we have a linux machine acting as a router/firewall, and I like all the control you get in this kind of setup compared to having a consumer grade router that ISPs usually ...
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1answer
38 views

openSUSE installs and VMs constantly being hacked and bricked

Sorry if this is a total newbie question, but I'm doing frontend design work for a radical political organisation and ALL my installations of Linux, be they openSUSE, Ubuntu or Fedora keep getting ...
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2answers
10k views

Higher rmem_max value leading to more packet loss

The rmem_max Linux setting defines the size of the buffer that receives UDP packets. When traffic becomes too busy, packet loss starts occurring. I made a graph showing how packet loss increases ...
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21 views

Hostapd with ACS not working due to not collecting survey data

I'm trying to use hostapd in version 2.5 with ACS. In order to do that, I have used the following config file: interface=wlp2s0 driver=nl80211 ssid=ap-example hw_mode=g channel=acs_survey ...
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1answer
18 views

Segmentation fault when running nuttcp inside Docker

I am measuring the UDP throughput between two Docker containers that are connected by Docker's native overlay network. I already used iperf but also want to measure the throughput with nuttcp. But ...
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1answer
104 views

CentOS port forward

I have the following situation: Internet ----- Server ------- virtual machine (kvm) public ip 192.168.122.12 x.x.x.x I need to make service on the port 3333 ...
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2answers
34 views

KVM - Access from an external computer to the Virtual Machine

I have the following setup: Notebook (IP: 192.168.1.100) Host: (IP:192.168.1.129) Both Notebook and Host are connected to a router (Internet IP:192.168.1.1)¨ The host (Host) has two virtual ...
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1answer
10k views

How to block internet access to certain programs on Linux

Recently, I have encountered a problem of limiting Internet Access to specific programs. Could anybody recommend a good way of doing that, without using any particular software?
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11 views

Quagga OSPF not updating

TL;DR: routing daemon not updating tables. Help! Consider two different Linux vm's configured for routing, R1 and R2, which are directly connected on 10.0.0.0/24. Each has other networks on their ...
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34 views

Route all the trafic using iptables nat in linux

I'd like to route all the trafic through iptables NAT in linux, I'd like to route all the traffic through TOR. My script is accepting only TCP and UDP protocols, but I need to route all the protocols ...
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2answers
95 views

How to setup a netem box

I'm trying to simulate different network condition based on factors such as latency, bandwidth and so on. I found that Netem is the best way to simulate different network condition. So my desired ...
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1answer
43 views

Can Linux be made to honour IPv6 Route Advertisement preferences?

Bottom Line Up Front: I can't get a Linux box receiving RAs to use the RFC4191 "Default Router Preference" value to prefer higher-priority routes. Instead, whichever default route it learnt first is ...
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48 views

VRF on Linux using network namespaces

My ultimate goal is to implement Virtual Routing and Forwarding (VRF) in Linux. The method that seems to be most widely accepted is to set up different network name spaces (one for each separate ...
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2answers
3k views

Siege: descriptor table full sock.c:119: Too many open files

I am trying to make a stress test in my own server using siege with the following command: $ siege -c 500 myweb.com/somefile.php But I get this error: [error] descriptor table full sock.c:119: Too ...
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0answers
23 views

Right way of measuring overlay network performance

I am currently examining the performance (especially UDP throughput) of different Docker overlay networks. I do this by creating point-to-point connections between two hosts that are connected with a ...
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1answer
104 views

How would I get this routing to work between the two subnets? Unsure if i am over-complicating my network

I am attempting to operate 2 subnets, the first subnet on range 192.168.0.0/24 is free to access anything it wants, including machines on the second subnet. the second subnet on range 10.0.0.0/24 is ...
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1answer
26 views

Bridging of Internal Network in KVM

I am working on a project regarding deployment of VMs as internal network, which should be accessible from external LAN, in KVM. I am stuck in bridging these virtual machines. My setup consists of ...
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1answer
32 views

How to forward a port from guest to host in qemu (kvm)

Is it possible, and how, to forward a port from guest to host in qemu/kvm? Note do I mean (out of) from guest to host, and not from host into guest (that's widely documented). I think I'm looking ...
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1answer
61 views

PFSense IPSec and NAT

Due to bad design and hosting provider constraints I have a network where I don't control the router. Our network: 172.16.0.0/12 - LAN x.x.x.0/24 - WAN (Router is connected to the switches, we have ...
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13 views

Airodump-ng Not Showing Anything

I am using Kali Linux to test some adapters. First of all, I don't know why, but I have a wlan0 and wlan1. I have tried both of them and I still have the same problem. So far I can issue the command: ...
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what makes RPS different from IRQ balance

i was reading about RPS[Recieve Packet Steering] and how it makes Packets distributed on different cpus. I believe IRQbalance also does the same thing by distributing interrupts on different cpu. ...
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1answer
10 views

Trouble routing between interfaces on KVM host

Summary: VMs on host in different subnets can reach each other, but VM on subnet B cannot contact host's interface on subnet A. I am not sure if this is a product of my lab setup and firewall rules, ...
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1answer
3k views

Error while bringing up eth1

I'm getting this error while bringing up my network card: (process:2550): WARNING **: _nm_object_get_property: Error getting 'State' for /org/freedesktop/NetworkManager/ActiveConnection/3: (19) ...
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1answer
31 views

IPTables Configuration to allow all connections, only close/deny once data is sent

I'm looking to set up my IPTables firewall in such a way that: Any new connect() is accepted Once data is received: If the destination port is on a whitelist, continue allowing the connection and ...
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4answers
11k views

How virbr0-nic is created?

How can I create a virtual network interface like virbr0-nic? I am trying to find a way to create a NIC like virbr0-nic but everything which I can find on the Internet is how to create an interface ...
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1answer
22 views

CentOS: How to create a default route after server starts

I'm using CentOS 6.7 on Proxmox KVM. Now I would like to get my network-connection working. This is my config: Now I have to perform ip route add 89.xxx.xxx.1 dev eth0 and ip route add ...
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2answers
1k views

iftop Shows Lots of Mysterious Connections - Not Showing in netstat

I've just stopped all pretty much all services except sshd on my server (Ubuntu Server 10.04), and when I run iftop I get output that looks like this: 12.5Kb 25.0Kb ...
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1answer
22 views

Unable to access Node Server from external network

I have a VM with two public IPs. I have installed OpenStack controller node on the VM. I have access from the external network to Horizon and Keystone service running on apache2 web server on ports 80 ...
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2answers
1k views

what does `pipe <number>` mean in `ping` output?

While running a test to diagnose some alleged network problem, I got this output from ping: --- r01c01b11n02 ping statistics --- 30000 packets transmitted, 29995 received, 0% packet loss, time 6309ms ...
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Capture no-modified packet with iptables

I have a user-space program in which I process packets. I send them there with help of iptables. The problem is that I capture not original packet but modified. I have wlan0 interface up with access ...
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4answers
22k views

Intermittently high ping times to router via Wi-Fi

On my local network there are (among others) 5 machines (running Debian Jessie or Arch) wirelessly connected to a Netgear WNDR4000 router. Below is a graph of the ping times to the router from each of ...