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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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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227 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
250 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
85 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
105 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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50 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
513 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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1answer
39 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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2k 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
53 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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0answers
113 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
97 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
205 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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0answers
41 views

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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34 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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1answer
57 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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2answers
143 views

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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1answer
81 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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2answers
60 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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2answers
381 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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0answers
53 views

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
49 views

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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1answer
103 views

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
82 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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1answer
92 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 ...
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1answer
124 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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1answer
52 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
38 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
86 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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0answers
119 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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3k 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
48 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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1answer
69 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 ...
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2answers
61 views

How to forward traffic to different nics based on source?

I'm a newbie to IPtables, but am looking to do send traffic to a specific card based on the source. Here's what I would like: eth0 - all traffic comes in on this NIC Depending on the source IP, I ...
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26 views

allow double tagging on vlan interface

I have a single interface eth0 on my machine. I have a linux bridge to which If I add my interface I loose connectivity. So I create a vlan interface and add it to the bridge. All is fine now except ...
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1answer
47 views

ip route command with source option

I have multiple interfaces on my system catering to different subnets. I also have a pseudo interface which is a p-to-p driver for tunneling packets. I was trying to add routes using ip route command ...
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268 views

Linux: Reduce UDP Packets Error

I'm facing UDP packet receive errors (under Linux 'netstat -su' command). I have 10 x UDP processes running on Machine-A (RHEL 5.2) and each of them send 290-byte packet at 50 times per second to ...
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1answer
60 views

Mount a SFTP remote filesystem that doesn't give shell access

I have a NAS that exposes its filesystem as SFTP, but it doesn't give any access to connect throught SSH as a normal user. I've tried to use sshfs to mount it from a remote webserver, but I receive ...
0
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1answer
44 views

How to achieve stateful fail over when using multiple uplinks?

I have multiple ISP lines over which I am load balancing the network traffic on my linux machine having multiple interfaces ( eth0, eth1 ,eth2, eth3) . This I am doing by creating the routing tables ...
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2answers
147 views

DNS points to the right IP, but I can't connect using DNS

UPDATE: This is now strictly a local problem, connecting remotely works (a dumb mistake I made.) I think it's now it's a loopback issue, which is a different issue, and likely answered in another ...
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22 views

Fail over in Lokiwall Firewall

I have configured lokiwall firewall on my linux machine having multiple interfaces. Dual Routing works fine. However, I wanted to know how does the fail over happen in case a link goes down. Do the ...
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0answers
95 views

Separate L2TP/IPsec VPNs with dynamic VLAN assignment

I am working on a Linux (Debian 7) VPN concentrator for different kinds of remote access. One of the offered protocols is L2TP/IPsec because of the client availability. I am using xl2tpd which in turn ...
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1answer
69 views

Debian port(s) not responding

I am fairly new to servers. I am trying to run a shoutcast server on debian. Shoutcast runs on a default port of 8000. My problem is it will not load when visiting xxx.xxx.xx.xxx:8000. When I log in ...
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1answer
120 views

iptables destination NAT from one range to another

I am trying to make destination NAT from one range (192.168.2.0/24) to corresponding ip addresses in another range (192.168.1.0/24). I have managed to do this ip by ip iptables -t nat -A PREROUTING ...
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2answers
2k views

Telnet client on redhat linux

I am trying to install a telnet client in Red hat linux server which doesn't have internet connectivity. Red hat linux version less /etc/redhat-release Red Hat Enterprise Linux Server release 6.4 ...
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1answer
191 views

bacula backups very slow with TCP socket in 'unkn-4' state

Several bacula-fd clients are backing up to one bacula SD (using 2G disk files on massive RAID, not tape), usually 2-3 of them concurrently. It works fine, except when 2 bigger clients (about ...
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31 views

Why does ip_forward=1 cause inadvertant problems?

I did a google search and searched the Ubuntu forums, but couldn't find the answer I was looking for with my specific situation. What I have is the following: 2 handsets setup for VOIP ...
2
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1answer
390 views

Passing through RDMA network devices to docker containers

I'm wanting to passthrough infiniband to a docker container so that I can run some high performance apps over ipoib and use rdma. Currently, I'm doing this with xen virtual machines. Now I'm looking ...
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1answer
60 views

Forwarding traffic from one virtual interface to another

I have a router with two ethernet interfaces: eth0: 1.1.1.2 (with 1.1.1.1 gateway) eth1: 2.2.2.1 I created two new virtual interfaces: eth0:1 : 1.1.1.3 (with 1.1.1.1 gateway) eth1:1 : 2.2.3.1 ...
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60 views

Redirect Default Gateway Traffic in Linux to File

I am trying to troubleshoot one of my linux servers (ubuntu server). Therefore I want to intercept all traffic that is sent to the default gateway and then write it to a file: preferably some kind of ...