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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Linux network configuration tools that will automatic restore old settings after a certain time [on hold]

Years ago, I have used a tool to change network settings. It will show a command line prompt to make sure the network settings are not broken. If it does not receive response after a while, it will ...
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52 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
22 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 ...
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2answers
35 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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27 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
39 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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1answer
25 views

Common ethernet settings for UDP when bandwidth usage is high [closed]

Suppose I have lot of servers which TX and RX lot of UDP traffic. Suppose I have 100 Mbps ethernet to use to TX or RX around 80 Mbps UDP traffic. And suppose I have 1 Gbps ethernet to use to TX or RX ...
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45 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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63 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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35 views

syslogd is attached to a remote IP address

I have a hosted server and I have 3 VM's on the server. I did a netstat -antup and noticed this: tcp 0 0 192.168.0.15:37023 73.167.119.19:21333 ESTABLISHED 4039/syslogd Does this ...
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7 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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44 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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Virtualbox: Incoming connections from arbitrary networks to VMs in host-only network appear as if originating at the gateway [migrated]

Configuration: Ubuntu 14.04 host Virtualbox 4.3.18 (from http://download.virtualbox.org/virtualbox/debian ) Ubuntu host functioning as a router - net.ipv4.ip_forward=1 Several host-only networks ...
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1answer
31 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 ...
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1answer
64 views

Redirect all traffic from multiple interfaces to single IP

I would like to redirect all traffic (specifically TCP & UDP) from multiple WAN interfaces (ppp0, ppp1, ppp2) to a single IP from eth0. When it comes to interface to IP, I can use the PREROUTING ...
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1answer
22 views

IPsec transport mode and MTU

[Similar to Right way to set the MTU of an IPsec Client (Linux/Racoon), but different in that there is no router on the responder side] I have a setup where machines in a local network need to talk ...
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1answer
39 views

conflict in network interface configuration of CentOS 6.5

I am trying to create 2 network interfaces, one with DHCP and the other with static IP on a CentOS VM running on ESXi Server. Content of file ifcfg-eth0 is as follows: DEVICE=eth0 ONBOOT=yes ...
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2answers
14 views

Is it possible to configure carp using /etc/network/interfaces?

Lots of tutorials out there show to set-up carp using ifconfig: https://www.netbsd.org/docs/guide/en/chap-carp.html I'm wondering if it's possible to do the same using /etc/network/interfaces? For ...
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1answer
62 views

Using Firewall-cmd to create address specific restrictions in centos 7

How do I create a firewall rule using firewall-cmd tool (new firewalld) such that I will limit specific network to access only one service and allow all on all service in one zone. For example: I ...
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22 views

Nginx response latency different on different port

I have two server connected to a same SW(HUAWEI S5700) with 1Gb link. I deployed nginx on one server and try to retrieve file from it in another server. In nginx I have two server configuration with ...
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1answer
30 views

How to check what application is requesting port? [duplicate]

Is it possible to check which application is requesting specific port in a debian server? I'm getting a ton of these in iptraf: x x UDP (77 bytes) from 172.16.0.2:25748 to 212.59.1.1:53 on eth0 ...
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103 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 ...
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2answers
17 views

Bind dont forward to secondary dns server as specified in “forwarders” under named.options.conf

I have bind9 setup to forward dns queries to machines connected localy trough the 192.168.1/24 network. The ip's that I forward the queries to are also my internet gateways. Sometimes one of the ...
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43 views

Route traffic for a specific IP through a specific interface

I'm setting up a server that tunnels all its traffic over an OpenVPN connection. The VPN connection is further tunnelled over obfsproxy hosted on the same machine. The problem is that as soon as the ...
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2answers
54 views

IPv6 Stateless Autoconfiguration route advertisements

In our network, we have a Cisco router acting as the core router, connecting all our sites to the main site. We also have a Linux firewall connecting us to the Internet. Site 1 --\ ...
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1answer
98 views

Load balancing network traffic using iptables

I am trying to load balance traffic from internal LAN on a linux router having two gateways. Initially I went for the iproute implementation which didnt balance the load as expected, reason being that ...
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Dropped TCP Packets over two-stage IKEv2 VPNs

Something of a weird setup this: There are two Virtual Private Clouds (10.100.240.0/20 = prod1 and 10.101.0.0/24 = control), which have a valid router between them. Control hosts a VPN that is meant ...
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15 views

Configuring openldap/PHP LDAP against “signed” LDAP connections with Active Directory

This may sound like a stupid question, and maybe it's already been answered, but I can't find a definitive answer anywhere, so I thought I'd ask. When someone enables "Domain controller: LDAP server ...
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60 views

How to fixe codeigniter 404 Page Not Found in linux hosting

I have .htaccess as below code # Set PHP Time Zone: #SetEnv TZ America/New_York <IfModule mod_rewrite.c> #Option +FollowSymlinks RewriteEngine On RewriteBase / RewriteCond %{REQUEST_FILENAME} ...
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1answer
27 views

nmap: why is it scanning port 80 with TCP ACK and not SYN?

While reading nmap man pages, I read for the -sn option: The default host discovery done with -sn consists of an ICMP echo request, TCP SYN to port 443, TCP ACK to port 80, and an ICMP timestamp ...
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SSH works locally but not remotely

Recently ran into a hardware issue on my CentOS machine. After a PSU, ram, mobo and CPU replacement I think I have the hardware issue resolved. However, I believe I have a network configuration ...
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29 views

Hosts cannot ping in two name spaces using Open Vswitch

I have two name spaces red and blue. Red is connected to host1, and blue is connected to host2, but these two hosts cannot ping each other. Here is the commands that I put: ip link add host1 type ...
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how to use public ip in my private network [migrated]

I'm trying to use public IP address in my private network. In a short, how to set public IP, which is different to endpoint IP of my private network, to my server in my private network? Is other ...
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2answers
44 views

Port forward with iptables

I got lo (127.0.0.1) and eth0 (172.17.0.8). I want to redirect packets that land on 127.0.0.1:80 to 172.17.42.1:80 (route from eth0). I tried iptables -t nat -A OUTPUT -p tcp --dport 80 -d 127.0.0.1 ...
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linux: how to troubleshoot forwarded port? [migrated]

My home internet connection has a static IP address (eg: 123.123.123.123) I have configured my router to forward port 9000 to an internal host (192.168.1.101). That host is running Ubuntu 14-04. ...
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76 views

Add a VLAN tag to specific UDP port traffic

I'm running an application in Ubuntu12.04 that I've written that does some remote switch management. I have only a single NIC connected to the network of managed switches, eth0 which is set with IPv4 ...
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OpenVPN Client recieves reply from Ping to Server but not from eth0 or non-server IP

I have been using OpenVPN succesfully with Layer2 bonding for over a year now. I have been experimenting with a more complicated setup on the local LAN using a ProxmoxVE hosting KVM VM as the server ...
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1answer
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How to route an IP Whitelist to one VM and all other to a second VM on proxmox?

Is it possible on linux to have a whitelist of IP's that are allowed to reach a specific VM on the internal NAT? eg (public ip (proxmox) --> My VM for whitelisted IP's (192.168.0.1)), and if the ...
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Execute script on ipv6 prefix change [migrated]

How can I execute a script or program whenever my (world-routeable) IPv6 prefix changes? If there is (currently) no easy way to do this, a pointer to the corresponding Posix system calls would be ...
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1answer
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Cannot Ping Devices Across Interfaces for Shorewall Single IP Three-interface Firewall on Debian Wheezy

Summary I am currently working on a three interface software firewall using Shorewall 4.5.5.3 on Debian Wheezy, and I'm having some difficulty with the loc (eth2) and dmz (eth1) interfaces. The fw ...
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1answer
43 views

why linux bridge shows 2 mac addresses for one qemu vm?

I am new to qemu networking and pretty confused about the following situation. I launched 5 VMs. Each connects to br0 through a tap device. I also have a dnsmasq listening on br0 for DHCP. The ...
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39 views

LXC container clone has no network and SSH stopped

I was having this networking problem with LXC containers (question and answer here:bridging LXC containers to host network with different IP range) and if I have found a solution, I still have not ...
0
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1answer
95 views

VMs on ESXi system, only able to use internal IPs

first off I am a bit of a network newb, I know the basics but that is about it. So I have a ESXi server running a few VMs. The set up is; -Master IP (controls the ESXi box) -Internet IP (for general ...
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23 views

How to change the ip range used for an IPCOP network interface

I am using IPCOP v2.1 I currently have a blue network with the range 192.168.0.0/23. I would like to change it to use 192.168.200.0/23. Is there a way to simply make the change, or am I required to ...
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1answer
29 views

Most outgoing connections blocked (kind of?)

I have a server which I upgraded from Ubuntu 12.04 to 14.04. Now I have some extremely strange behaviour (which I believe was not present immediately after the upgrade, but can't be sure): I can't (by ...
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1answer
33 views

rcp files from windows 2008 server to linux box? (Running rcp on linux)

I am trying to run rcp command on rhel6 server to copy over files from a windows 2008 server but see this error message. /usr/bin/rcp administrator@10.225.185.112:"C:\nfsqa-rhel62-vm01.root.keytab" ...
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52 views

How to route traffic through different interfaces based on the port number?

iptables -A PREROUTING -i usb0 -t mangle -p tcp --dport 8080 -j MARK --set-mark 1 iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain ...
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2answers
429 views

OpenVPN Route Client Traffic Through VPN Server Tunnel

I have configured a vps following this tutorial, the server and client are successfully connected and can ping each other, server is at 10.8.0.1 and the connected client (android-OpenVPN Connect) get ...
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1answer
36 views

Temporarily block communication with host if its connecting to port X

I have a Linux VPS, and it's constantly being scanned, bruteforced by some rogue IPs. This VPS is my private server, that serves only to me, and I'm the only user of it. Also I am the only user who ...
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44 views

Linux router: User friendly, web-based traffic monitor app [closed]

This is not a tech question but I hope someone can help me out. I've been searching all over the web for an app like this, but I can't seem to find one: Friendly user interface where a non-technical ...