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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2answers
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Check on Linux certain port is occupied

I'm writing a script that will spin up server that want to use certain port number. In some occasions this port is occupied. I want to know how to check it in bash so I can react in proper way. How ...
2
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1answer
56 views

Possible to force TCP window scaling to a higher value?

Is it possible to increase the TCP window scaling factor on Linux (CentOS 7.2)? I have a long fat network (100 Mbps) from London to Chicago and I'm getting 16 Mbps throughput in TCP on an sftp from a ...
0
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1answer
38 views

Resolve NetBIOS names without full qualification

I am connected to my office VPN and I can successfully RDP into my computer using the fully qualified name for it PC00001.myofficevpn.plc. When I try to connect using only the hostname PC00001, I do ...
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0answers
16 views

Smaller subnet mask to “merge” VPN-connected LANs?

I have two LANs connected to different internet connections (in different cities, in fact): ISP1 -> LAN 1: 192.168.10.0/24 ISP2 -> LAN 2: 192.168.11.0/24 On each LAN is a router. Both routers ...
0
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1answer
29 views

Routing only internal traffic to VPN

When I connect to the VPN, I don't have access to the internal addresses of my office. If I issue a: route add default dev ppp0 I can finally ping the office's machines but all my internet traffic ...
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1answer
28 views

Tunnel / Forward connections on server 1 to server 2

I have now spent some time researching, but I haven't found a working solution to the following problem: I want to tunnel any requests on server 1, port x to server 2, port x. The port stays the same,...
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1answer
25 views

frequent delay of 5-10 sec in sending commands from putty redhat. Why?

When we type a command from putty, it suddenly hangs for a period of 5-10 sec or more, but the commands are sent to terminal later. So seems to be a latency which occurs frequently. But, I might be ...
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0answers
10 views

Dhcp id: user: no such user , dhcp start error Centos6/ rhel 6

i installed dhcp server using rpm o rhel 6 when iam starting #service dhcpd start/restart i am getting Failed to start dhcp, even when i am running #id dhcpd getting error no such user (no group ...
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0answers
22 views

What is the network connection speed between two containers communicating via a virtual bridge running on the same host?

Does a virtual bridge (added to /etc/network/interfaces) limit the transfer speed of data from the memory of one lxc/docker container to another? For example does the memory throughput drop to that ...
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0answers
66 views

Configuring vxlan unicast in linux

I want to try vxlan unicast and configured following configurations in Fedora 23 VM1(enp0s8) ========= (enp0s8)VM2 ip address add 100.1.1.1/24 dev enp0s8 ifconfig enp0s8 up ip link add name vxlan42 ...
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1answer
89 views

get mac address and replace from a file [closed]

I have two interfaces ethernet: Example: ifconfig | grep direcciónHW enp2s0 Link encap:Ethernet direcciónHW b8:2a:72:01:01:02 eno1 Link encap:Ethernet direcciónHW 9c:d2:1e:01:03:04 I ...
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0answers
22 views

Bridge not functioning as expected

I want to put a listening machine in my test network using a bridge setup. I now have the following test setup: PC1 (192.168.40.250/24) --- Bridge (192.168.40.160/24) --- PC2 (192.168.40.132/24) ...
0
votes
1answer
42 views

Linux server failing to send SYN/ACK after receiving SYN remotely, works locally

Problem: A server process can be accessed by a device on the LAN or by the server itself, but it cannot be accessed outside the LAN (port forwarding is configured correctly as the server does receive ...
14
votes
5answers
2k views

How to simulate DNS server response timeout?

I need to test an application's behavior when it can't resolve a hostname due to a timeout. Setting nameserver 127.0.0.1 in /etc/resolv.conf didn't work: the relevant functions return immediately with ...
0
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0answers
36 views

Public port forwarding from site A to site B (connected through a site-to-site VPN)

I have two distant offices (site A and site B). The two offices are connected through a site-to-site OpenVPN solution (the VPN servers are independent of the office routers, each router has a static ...
3
votes
1answer
138 views

Create a multi-homed linux load balancer with two internet connections and one LAN connection

OK,... this has possibly been answered, unfortunately, I have not found anything that looks like it might be the resolution. Ive looked at these pages and they have some useful information, but not ...
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0answers
33 views

Configuration SNAT iptables in ubuntu

I have 2 PC be created by VMWARE 1. PC1 (make iptables router): eth0 's IP: 192.168.1.4/24 (network connection is bridged) eth1 's IP: 192.168.2.2/24. (network connection is wmnet9) 2. PC2: ...
0
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1answer
62 views

Virtual NICs and Host only adapter in KVM

How can i create virtual network adapter like a physical eth0 in KVM? As I lack physical NICs. Also I need a Host-only adapter just like in VMware to connect two VMs in KVM. What is possible solution ...
0
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1answer
32 views

debian networking does not restart properly

I have a Debian 8 machine, where I've configured two VLAN interfaces in /etc/network/interfaces. Now I've deconfigured it (deleted information from interfaces file), restarted networking, and now it ...
0
votes
1answer
42 views

Network Related Apache 2.4 403 Authz Error AH01630

I've never seen this style of behavior before. If I access this site on most networks it works. However if I am on-site of the client I cannot pull up the site. TWC Home, works fine. ATT Cell Data, ...
1
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0answers
51 views

How to connect to a service on a local network machine whch which only listens to localhost?

I have a service which only listens to localhost on port 7400. There is a service running on a windows and an ubuntu machine on a private network. How can another computer on the same network ...
2
votes
1answer
59 views

Simulate massive network traffic [closed]

We want to stress test our pfsense box with a massive amount of connections and traffic. Right now we are using iperf, but reaching a number of more than ~300 parallel connections the test clients ...
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votes
1answer
47 views

Connected to router but without internet [closed]

My Linux Mint 17 box is connected to a router via eth0, of which is connected to the internet. However, my box cannot access websites or ping google.com etc. I am sure the problem is with the DNS ...
0
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0answers
34 views

Transparent Bridging of Internal Network in KVM

I am deploying a following topology of virtual Honeynet in KVM.Topology of Honeynet I have two network interfaces eth0 and eth1 ony my System. Problem I am facing is to implement transparent bridge i....
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votes
1answer
73 views

If a server is headless (CentOS 7) is there a way to make the GPU used as an extra CPU core?

I've got a server with centOS that has no graphical interface. I only connect to it via ssh. As a result, the GPU is probably not used for much. I'd like to make the server use it as an extra CPU core....
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2answers
42 views

how to execute a script Rhel 7 at booting time?

I am trying to execute a shell script on RHEL7.1 when the machine starts. As in ubuntu, Upstart scripts (in /etc/init/) are used to execute any scripts or to start any services at boot time, is there ...
1
vote
0answers
42 views

Proxmox: Add IPs from different subnets to LXC-container

I am using proxmox 4.1. If I add IP-addresses to my CentOS-7-LXC I can only do that if this IP is from the same subnet. If I'm using another subnet with another gateway the container is not pingable ...
0
votes
0answers
33 views

IPv6 interface not responding to neighbor solicitations, DHCP involved too

ip addr shows: 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 02:6d:5e:86:29:49 brd ff:ff:ff:ff:ff:ff inet X.X.X.X/...
0
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0answers
65 views

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 works ...
2
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2answers
94 views

why Ethernet MTU size is 1500? [closed]

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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4answers
110 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 ...
0
votes
1answer
63 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 $ ...
1
vote
0answers
25 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 ...
0
votes
1answer
53 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 ...
1
vote
1answer
41 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 ...
0
votes
1answer
28 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?
0
votes
1answer
44 views

Running LAN services on a router/firewall [closed]

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 ...
2
votes
1answer
47 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 ...
1
vote
1answer
47 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 ...
0
votes
0answers
161 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 macaddr_acl=...
3
votes
1answer
37 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 ...
0
votes
0answers
28 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 ...
0
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0answers
51 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 ...
0
votes
1answer
117 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 ...
2
votes
0answers
146 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 ...
4
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0answers
42 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 ...
0
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2answers
46 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 ...
0
votes
1answer
88 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 ...
1
vote
1answer
129 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 ...