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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iptables connlimit: exclude multiple IP addresses

I have currently this IPTABLES command: iptables -A INPUT -s ! 192.168.0.2 -p tcp --syn -m connlimit [...] -j DROP As far as I know, such rule limit some number of connections following various ...
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0answers
80 views

Routing with multiple NICs on debian

I have a machine with two NICs on different network segments, I've set up routing for the different segments. It works if I run all the routing commands manually, but I can't get it to work when ...
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2answers
102 views

Postfix - How to prevent external clients from using my server as a relay? [closed]

I have a postfix server installed on Ubuntu 14.04. A PHP script running on the machine uses it to send outgoing email. Additionally, I use postfix to receive mail sent to a local account, which is ...
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0answers
32 views

How to check a given connection has been offloaded to network card

From what I read, some part of the tcp protocol operation can be offloaded from kernel to network card driver thanks to TOE (or GSO, LSO, LRO..). My objective is too find if a given socket has some ...
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87 views

Route sql server traffic through firewall

We currently host our web application on multiple servers using Rackspace Auto Scale. This causes our outbound IP addresses to regularly change. At the same time we need to connect to an external sql ...
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1answer
217 views

Linux clients can't connect, server and TCP Windows Size / Timestamps issue

We have a problem that a number of clients (all linux Ubuntu) are sometimes not able to connect to a remote server over SSH. If the problem occurs, Windows clients don't have that problem and can ...
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1answer
359 views

Multiple IP addresses per NIC on Ubuntu Desktop 14.04 [closed]

I have read a lot of tutorial about how to add virtual IP addresses per NIC but it doesn't work for me. All tutorials that I must edit /etc/network/interfaces but when I restart the service, I always ...
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2answers
158 views

Supersede default route

I have two network interfaces eth1 and wlan0. I would prefer all outbound traffic to go through eth1 before wlan0, but if eth1 is not up, and then wlan0 should handle the traffic. Both interfaces get ...
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2answers
190 views

In an OpenVPN network, Windows clients cannot access the host and other clients

I have set up an OpenVPN network and I'd like to let every client in the network be able to connect to each other, ie. servers 10.8.0.1, 10.8.0.2 and 1.8.0.3 should be able to communicate over VPN and ...
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0answers
132 views

SolusVM KVM-Virtualisation: Add IPs from multiple Subnets to VPS

I would like to add IPs from different networks to my SolusVM-KVM-Virtualisation. The virtualisation is working fine and is accessible via 81.95.3.xxx. But other IPs I added (82.199.134.xxx) are not ...
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0answers
59 views

Rsync does not delete destination files [rsync protocol / module]

An automatic backup script executes the following rsync command to sync a local directory tree with a remote one: env RSYNC_PASSWORD=$rsync_password rsync -aqrxz --delete --timeout=30 \ ...
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3answers
643 views

How to detect what's blocking my incoming traffic on Ubuntu 14.04 LTS, if it's NOT iptables and NOT EC2 Security Group?

I have SSH root access to an EC2 instance. It's Ubuntu 14.04 LTS. I have nginx web server listening on all interfaces on port 80 TCP. It's accessible from this server but not from the outside. ...
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2answers
486 views

What is causing the famous “broken pipe” when I use tmux inside an SSH session?

Scenario1: I SSH from my employer (OSX Yosemite SSH client) to my home server (Debian stable) and (re)connect to a tmux session. If I leave the terminal inactive for a while (~20minutes), it seems ...
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0answers
53 views

GRE Tunnel Collapsing in One Direction

This is a related question to another thread I posted. I'm having an issue where my GRE tunnel is collapsing in one direction, but can be reopened by ping the other server using the GRE Interface. ...
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1answer
261 views

Multicraft: Port Forwarding through a GRE Tunnel

For the past week I've been attempting to protect a server from DOS attacks by utilizing a GRE tunnel from a VPS to a dedicated machine without much success. Visual: User --> VPS --> Dedicated ...
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2answers
394 views

How to configure a Linux network namespace that allows UDP broadcast

I'm trying to use the ip netns family of commands in Linux to create a network namespace in which I can run a program that uses UDP broadcast. I do not need access to the Internet, or any interface on ...
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0answers
43 views

What are the advantages NAPI before the IRQ Coalesce?

As known there are two approach to avoid some overheads of hardware interrupts in highload networks, when there are too many hardware interrupts, that switching to them takes too much time. It is very ...
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1answer
531 views

Cannot ping to localhost into CentOS

I'm connecting to my server (Centos 7) with ssh and I try to ping to localhost: ping 127.0.0.1 but doesn't work: ping 127.0.0.1 PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data. ^C --- 127.0.0.1 ping ...
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1answer
45 views

How increase classes in HTB? [closed]

I am trying to setup a traffic shaping by HTB and tc. I have 70,000 users and I want to control the bandwidth of each user, so I create 70000 classes, and assign each ip address to a class by ip ...
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1answer
38 views

IPSEC stack low speed

I am working on Openswan IPSEC Implementation for Linux-kernel 2.6.35.9 My concern is when i do speed test using IPSEC kernel Images and without running IPSEC service i get speed of 40Mbps and ...
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1answer
108 views

measuring network throughput with netperf

I'm doing benchmark test of Linux server using netperf. According to information at networksecuritytoolkit the theoretical max throughput rate for 1514-bytes packets is 117.35 Mbp/s. However I'm ...
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2answers
184 views

Using iptables or similar to redirect traffic to a proxy

I've searched around for an answer to this question, but it seems like most of what I found wasn't specifically what I wanted to do (mostly redirecting traffic on the same host to squid running on ...
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1answer
126 views

Changing qemu/libvirt default gateway IPv4 IP to something other than x.x.x.1/24

General info: I have a KVM-libvirt/qemu running on ArchLinux; 3.18.2-2-ARCH ls | egrep -i 'libvirt|qemu' libvirt-1.2.11-1-x86_64.pkg.tar.xz libvirt-glib-0.2.0-1-x86_64.pkg.tar.xz ...
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1answer
195 views

TCP Upload Speeds Slow to the Internet over LFN

I've got two Linux VMs separated by a 50 mbps WAN connection. There is about 70ms of RTT on this WAN link, so it's got some latency. I've been testing my upload throughput to the Internet from each of ...
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7answers
17k views

Can't start CentOS 7 “network” service

I Can't start CentOS 7 "network" service after disabling and removing "NetworkManager" service. When I check the network service status, it comes up with the following error: #systemctl status ...
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1answer
59 views

Difference between ip link eth down and ip link dev eth down

What's the difference between ip link set eth0 down and ip link set dev eth0 down ? The difference between the commands does not appear to be documented anywhere.
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0answers
155 views

How to create openvpn tunnel between multiple interfaces between two hosts ubuntu linux

I want to create OpenVPN tunnel between two Ubuntu 12.10 hosts which has two interfaces, say: Host1: eth0, eth1 Host2: eth0, eth1 A tunnel is wanted between: Host1 (eth0) <-> Host 2 (eth0) ...
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0answers
86 views

How to config private IPs for IPMI using VPN?

Recently I discovered it is best to protect my IPMI web interface behind a VPN. I went ahead and installed OpenVPN on my server and connect to it using tunnleblink on OSX. The VPN part is all set and ...
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1answer
74 views

Debian-based Infiniband point-to-point Voltaire dual port cards

I have the following configuration: I------------------I I------------------I I I(P0)---------(P0)I I I Voltaire HCA 0 I I ...
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1answer
105 views

how to make this bridge to work?

I have posted a similar question at: http://stackoverflow.com/questions/27873819/customising-docker-network-doesnt-work# To simplify the question, let me get rid of docker. This is the network ...
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1answer
129 views

Windows multicast NLB with Linux clients

I'm (on behalf of a client, anyway) having some troubles with Linux accessing a multicast NLB cluster hosted on Hyper-V (waiting for more information on what version, but I don't think the version is ...
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1answer
2k views

Allow OpenVPN client to push it's own DNS servers, regardless of OpenVPN server's pushed dns?

There is an OpenVPN server running on a Debian and it pushes a DNS in the server config file: push "dhcp-option DNS 8.8.8.8" Is there an option to allow the users to change that DNS servers on the ...
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1answer
39 views

Why adding a route here is throwing up an error?

I have a linux Fedora -16 machine that has two interfaces - em1 Link encap:Ethernet HWaddr B8:CA:3A:89:EE:F1 inet addr:136.170.195.17 Bcast:136.170.195.255 Mask:255.255.252.0 ...
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1answer
190 views

Expose internal LAN to VPN using CentOS FirewallD

I have a (tinc) VPN setup with multiple clients that connect to a VPN server that sits on a LAN behind a firewall. I want to expose that LAN to the VPN that server is serving. I've seen a few examples ...
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2answers
123 views

how to force linux to accept packet with loopback ip

i have an embedded system with an Ethernet interface that needs to accept external packets with IP of 127.x.x.xx. is there a way to force Linux to accept external packets with this loop back address ...
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1answer
64 views

Public IP not responding because routing table…?

Fixed with: /etc/iproute2/rt_tables 1 tble_eth0 /etc/sysconfig/network-scripts/route-eth0 104.000.64.0/18 dev eth0 src 104.000.65.38 table tble_eth0 default via 104.000.64.1 dev eth0 src ...
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1answer
599 views

How to set ethernet devices to specific hardware on Centos 7

I have a Centos 7 system where I've disabled the new network naming system and reverted to the old system (eth0, eth1, etc.). I've done this because I'm using this in an RDO Openstack setup, and this ...
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0answers
105 views

How to add additional network segment?

Long-standing network (A) is as follows Network A: 192.168.37.0/24 GatewayA: 192.168.37.1/255.255.255.0 (eth1) ADSL on ppp0 (via eth0) Kernel IP routing table Destination Gateway Genmask ...
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4answers
362 views

Simulate slow connection between two ubuntu server machines

I want to simulate the following scenario: given that I have 4 ubuntu server machines A,B,C and D. I want to reduce the network bandwidth by 20% between machine A and machine C and 10% between A and ...
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1answer
264 views

Unable to set eth0 autoneg off speed 1000 duplex full : invalid argument

I use Ubuntu server for my things,but when i config speed 1000 and duplex full the error occur. I've tried the answers from here,does not work, the command i used is ethtool -s eth0 speed 100 duplex ...
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2answers
592 views

How do I block incoming traffic from Amazon AWS IPs?

I'd like to block ALL incoming traffic from Amazon AWS IPs. They publish a list of their IP addresses in json format here: http://docs.aws.amazon.com/general/latest/gr/aws-ip-ranges.html I have a ...
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1answer
368 views

Dummynet Filtering not working on FreeBSD 10

I am trying to do network emulation using dummynet in FreeBSD 10. I have this working in 9.3 however things must have changed and I cant determine exactly what but my setup no longer works. I have ...
5
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2answers
137 views

How do I set up docker containers to communicate on private network?

I have a small cluster at rackspace with a private network in the range 192.168.3.0/24. I would like my worker services to talk to each other using this network but can't figure out how to get docker ...
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223 views

OpenVPN server cannot ping client (routing/iptables issue?)

I am not sure exactly where the issue is here. I'm fairly sure that this is some NAT or iptables issue on the OpenVPN server but am lacking the networking know-how to fix the issue. The crux of the ...
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1answer
98 views

Is Linux limiting my application's UDP transfers, and how can I see it?

I am currently developping two applications to work over a custom video streaming "protocol". Basically: The server captures video frames from a webcam, slices them into parts, and sends these parts ...
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0answers
106 views

linux not replying to an arp request

I am running linux 3.14 on a system with 2 interfaces. on the first interface, i can access our local network. on the second interface, arp packets come in but linux doesn't send out reply. is it ...
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2answers
200 views

Performance Tuning Linux [closed]

Performance Tuning/ Monitoring/Latency keeping in mind I see following 4 items & in each item they are lot of tools. CPU Memory IO Network What I see following tools we do use. vmstat mpstat ...
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0answers
12 views

promisc mode doesnt work - better solution?

I have a Debian Wheezy server running snort with two network cards: eth0 and eth1. Eth0 is used to recieve a packet stream to inspect by snort - while eth1 is used by the admin to connect to the ...
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2answers
132 views

Can't connect to MySQL from another server

I have two servers on the same subnet. 192.168.100.1 (mysql) 192.168.100.2 (php) MySQL seems to be running fine on it's box but I can't seem to connect to it. These are both ubuntu boxes and ...
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1answer
721 views

Stale Network connections to Tomcat AJP port

I have Tomcat Application server connected with Apache server using mod_jk connector. Both are running on different servers. Apache ----->------ Firewall ----->------ Tomcat For the last couple of ...