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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3
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1answer
17 views

Please clarify for me how tcpwrappers works

We've recently gone through a security audit and among several valid and other, quite pointless findings is one that states that tcpwrappers is not disabled. I've never used tcpwrappers so I don't ...
0
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0answers
8 views

What part of the reboot cycle in Linux is WinSCP detecting as FTP port 21 being available?

When I rebooted one of my boxes running Ubuntu Server LTS 14.04.1 today, I received a strange message from WinSCP during the automated reconnect attempt that I've never seen before: ...
0
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0answers
7 views

Why some iptables DNAT rules stop working after some times until reboot?

After a while some of my iptables DNAT rules stop working. If I reboot my server, all of the rules work back. Desciption of the architecture : Tens of hosts (senders) send some UDP packets (one-way ...
1
vote
1answer
39 views

How to make a simple script that increases a number character by 1

I have to add a single command for MANY vlans, and wondering if I can generate a simple text file somehow? Then I can simply paste the text file into the network switch and it will add the needed ...
0
votes
1answer
22 views

Why are eno1 and eno2 in this order?

I've just installed a Fedora 21 Workstation system, and it's reversed the order of eno1 and eno2 from the CentOS 6 system that was on here before. lspci | grep Eth 00:19.0 Ethernet controller: Intel ...
0
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0answers
7 views

what is the value for setting a hostname in installation of oracle enterprise linux r6u5 should have? [migrated]

I am installing oracle linux r6u5 for my personal use in vmware workstation. While going through installatio i came to a point where I have to enter hostname, format specified init is ...
1
vote
2answers
28 views

how to check the number of connections open towards internet from a linux server?

We have issue where the response time from a endpoint is specifically having more response time for one server but not on other server. Further we found that this issue happens for all endpoint which ...
0
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2answers
31 views

Multiple IP addresses on host and one on kvm

I've recently configured my network using advice from this question but now I need to configure this a little different. I'm using Debian distribution. I have one dedicated server with 3 IP addresses ...
0
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1answer
27 views

Networking in Linux KVM

I want to know if there is any other way other than using linux bridges to interconnect interfaces from two virtual machines ? Since I am trying to run private spanning tree implementation in virtual ...
0
votes
1answer
18 views

How to duplicate multicast packets on several interfaces?

I would like to send a stream from a Linux server to several Linux clients via a multicast address. The clients are directly connected to the server but on different interfaces: bnep0 and bnep1. ...
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0answers
13 views

Linux Interface Collect Raw Bits [closed]

Is it possible to collect raw bits directly from a network interface? Seems like dd if=/dev/net/eth0 could work?
0
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1answer
23 views

forwarding packet from one interface to another interface

I have an embeded system with 2 interfaces e0 and m0, whose ips are 10.0.0.20 and 192.168.0.20, respectively. Incoming packets into e0 have an ip of 10.0.0.10 and should be forwarded to m0 interface ...
1
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0answers
14 views

How to use iptables or IFB to mark incoming traffic by device?

I'm trying to use iptables to mark incoming packets based on the device where those packets arrived (rather than their originating IP address or port etc), but haven't found a way of getting this to ...
0
votes
1answer
41 views

iptables v1.4.21: Couldn't load match `-d':No such file or directory

i am running kerenl 3.14.18 and using iptables 1.4.21, built with these options --static-enable --disable-shared. when i run this command: /sbin/iptables -A PREROUTING -m -d 127.3.0.2/24 -j DNAT ...
0
votes
1answer
22 views

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 ...
-2
votes
1answer
35 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 ...
1
vote
3answers
66 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 ...
1
vote
1answer
18 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 ...
0
votes
1answer
28 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 ...
0
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0answers
31 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, ...
3
votes
0answers
46 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 ...
0
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0answers
36 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:~$ ...
2
votes
1answer
46 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 ...
1
vote
1answer
22 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 ...
0
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0answers
26 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 ...
0
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0answers
25 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 ...
2
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0answers
27 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 ...
1
vote
1answer
28 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
38 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 ...
-2
votes
2answers
44 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 ...
0
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0answers
15 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 ...
0
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0answers
3 views

Error Messages when Inadyn reapplies IP to dynamic DNS on Raspberry Pi [migrated]

While i keep having access from outside my home network when hitting my "freedns" dynamic DNS, when typing "more /var/log/messages |grep INADYN" it gives me the errors below. I wonder what's wrong as ...
0
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0answers
36 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 ...
1
vote
1answer
59 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 ...
-1
votes
1answer
59 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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votes
0answers
38 views

Can't resolve Static IP Issues - CentOS 6

Let me start with acknowledging that this is a frequent topic on this site, and I apologize for asking it yet again. I have tried to use other online resources as much as possible, but I have not been ...
0
votes
2answers
58 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 ...
1
vote
2answers
52 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 ...
0
votes
0answers
31 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 ...
1
vote
0answers
28 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 \ ...
-2
votes
3answers
93 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. ...
0
votes
2answers
77 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 ...
0
votes
0answers
33 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
votes
1answer
102 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 ...
2
votes
2answers
86 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
votes
0answers
16 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
votes
1answer
190 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 ...
1
vote
1answer
37 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 ...
0
votes
1answer
23 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 ...
-1
votes
1answer
46 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 ...