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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Two IP addresses one network interface and virtualization

I have a Debian [H] host server with one network interface, configured like this (/etc/network/interfaces): auto lo iface lo inet loopback auto eth0 iface eth0 inet static address xxx.yyy.zzz.77 ...
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1answer
41 views

OpenVPN all subnets the same, send a single client to tun0?

The two networks in question are listed here.. The wlan0 is on 10.0.0.23/24. tun0 (openvpn) is on 10.8.0.6 but is routing traffic to the network 10.0/16. So both wlan0, and perhaps tun0 could have ...
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3answers
90 views

Is it wise to use OpenVPN to connect remote web servers?

I have a number of remote hosted servers for various purposes--web and application servers. I effectively want a "management network" of sorts so I can simplify tasks like log collection and package ...
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1answer
33 views

How are the routing tables populated on a Debian system?

How are the routing tables populated on a Debian system? I understand that the ip route family of commands can be used to manually manipulate the routing tables, but how are the routing tables ...
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1answer
61 views

Using a pfSense guest to firewall/route traffic for other guests

I was curious if this falls into the "why..." category or not. I have a dedicated, hardware UTM (Untangle) that's serving as an edge device with two hosts and a dozen guests behind it. Right now, I ...
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70 views

KVM Aggregate Throughput Limited at 1Gb - Virtio Queues Limiting Factor?

I have a KVM host with three NICs and can't get traffic between guests (in same subnet) above 1gbps aggregate. Is this by design and the only way to achieve >1gbps to use multiqueue support? So far, ...
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1answer
83 views

Linux Server Virtual Ethernet interface stops responding to arp requests

I'm hoping someone has had this issue before as it is driving me nuts. I have 2500 linux embedded Linux servers. We use these servers partly to act as gateways to other devices sat on a private ...
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0answers
453 views

How to configure VXLAN over linux bridge?

I am using Ubuntu 14.04 which support VXLAN configuration. Currently I can add a VXLAN interface such that: vagrant@ubuntu:~$ sudo ip link add vxlan1 type vxlan id 1 group 239.1.1.2 vagrant@ubuntu:~$ ...
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1answer
107 views

Sending Data extremely slow or RDS

I have the following two profiles for a basic SELECT STATEMENT: select count(*) from mturk_completion; Here are the two profiles: # My Local machine, using a local db Status ...
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1answer
47 views

Debugging a mysql connection

I am trying to figure out how to diagnose a mysql connection issue. When I run a group of queries locally on my machine it takes about 1s to run. When I run that same group of queries on an AWS ...
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91 views

Enable Netflow plugin in Ntopng

How can I enable the Netflow plugin in the latest Ntopng (1.2.2). There is no 'Plugins' option in the menus or I can't see it. I have logged in the web interface at port 3000 but there is no Plugins ...
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188 views

What are the pros and cons of large receive offload (LRO) vs generic receive offload (GRO)

I have been debugging a scenario where an ESX vmware host is communicating with a virtual linux machine via a virtual switch using TCP/IP. After a congestion event the vmware host is waiting for an ...
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0answers
50 views

Linux - Outgoing connections from process timeout after the process restarts

banging my head against the wall with this one... I have an Ubuntu Linux server, on top of which our own process which holds 40K persistent connections to external services. When the process ...
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1answer
98 views

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
72 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
84 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
27 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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74 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
175 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
252 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
125 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
158 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
107 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
47 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
443 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
351 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
49 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. ...
2
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1answer
221 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
302 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 ...
2
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0answers
37 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 ...
2
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1answer
416 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
43 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
31 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
88 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
151 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 ...
0
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1answer
103 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 ...
2
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1answer
161 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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5answers
12k 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 ...
2
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1answer
51 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
133 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
72 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
67 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
89 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 ...
1
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1answer
107 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 ...
1
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1answer
1k 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
32 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
165 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
111 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
62 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
450 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 ...