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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vnstat output giving different results

I ran vnstat -d and vnstat -m and compared the results to vnstat --dump. The values between daily and monthly are off by several bytes. Is this expected? I would imagine last months data and ...
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iptables setup forwarding between two ethernet interface

I want to create a gateway on linux which has 2 interfaces eth0 and eth1. Eth1 is created by a lte modem and once the lte modem attaches to the network and gets an ip address. Then a dhcp server is ...
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27 views

How to diagnostic internet access failure on a linux system?

I have a VM running on Xen. The virtual machine was running fine for months and suddently the network access broke down. Dom0 DomU .-------. bridge ...
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1answer
9 views

Opening a port to access a service in an isolated LAN

There is an isolated LAN (completely isolated, does not access outside and outside can't access it). But one of the server has 2 NICs, one of which is on our dev LAN and the other one in the isolated ...
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1answer
17 views

iptables TEE UDP traffic to a different subnet

I'm looking for a way to replicate UDP traffic received by one host to another host in a different subnet. The TEE target in iptables only works with gateways in the same subnet, i.e.: On the ...
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27 views
+100

Hyper-V lost synthetic NIC after Debian 8 dist-upgrade?

I'm running a Debian 8 vm on Hyper-V (Win Srv 2012R2) and when I did a dist-upgrade of stable, I lost all network connectivity. Using the console, I was able to see the network interfaces as UP but ...
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1answer
14 views

google api block request

We are using Google Adwords API to query out data. But the problem is that : After about 5 successfully requests , Google don't ACK to our SYN request as the image above. Did anyone face with ...
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1answer
27 views

Port forward linux iptables

My current network setup consists of a physical nic eth1 receiving my public ip from the modem. Next I have kvm/qemu virtual machines running on a virtual network using the ip range 192.168.122.0 - ...
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8 views

Captive HotSpot, Apple login callback issue

For some days I have been building a Wifi captive hotspot, from scratch. My question concerns Apple. It is working 90%: when I join my Wifi hotspot, the device (iPhone, iPad, Mac) displays a 'fake ...
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17 views

DNAT not forwarding to correct (local) IP address

I'm trying to port-forward a HTTPS service which uses different SSL certificates for each of the several IP addresses on the machine. Web server listens on each IP address on the internal port (444) ...
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1answer
19 views

Samba restart vs mount.cifs

My question is more about ensuring rather than an exact problem. I have a samba server (4.1) and I have a Linux client, which connects using this mount command: mount.cifs $SHARE $DIR -o ...
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1answer
49 views

OpenVPN server and client configuration for openwrt

I have an OpenWRT router with WAN(eth1) and LAN(eth0) interface. I wanted to install an openVPN server on this router, so I could access from the WAN side into the LAN side. My LAN(eth0) has a DHCP ...
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2answers
51 views

setting up linux router

I have setup three Ubuntu VMs in vmware. These are connected as: Now I want to use UBUNTU2 as router, so that when I run these commands in UBUNTU1, I get response from UBUNTU3, commands: ping ...
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1answer
15 views

How do you sync ipset sets across two machines?

I would like to replicate IPSet sets from one machine (server01) to another machine (server02) using rsync or btsync or something similar. Is that possible? If so how do I do it? This is a redundancy ...
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16 views

No package transfer from host to guest on KVM

I want to assign external static IPs to my KVM guests. I do not prefer a NAT solution. What should be the configuration of network and routing tables? I manually assing a static IP to guest. I can ...
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1answer
20 views

Iptables time-based rules having no effect - Gateway with 2 NICs

I have a network with the following topology: - WAN Modem with NIC facing the gateway: 192.168.0.1 - Ubuntu 14.04 gateway with two NICs: 1) Eth0 (facing the modem): 192.168.0.201 2) Eth1 (facing ...
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1answer
37 views

How to use conntrack to allow SIP traffic

I have the following problem: Device (eth0)----> SWITCH(trunk)+VLAN120 ---> (PC1) +VLAN200 ---> (PC2) I am able to ping from PC1 to PC2 which are in ...
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1answer
30 views

Gateway can't ping client

I try setup a new gateway in my virtual network. But sure I' have a problem. The Gateway cannot ping client but client can ping other client and gateway. So I have check my iptables rule (I does'nt ...
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29 views

Captive portal OAuth

Im building a large network of AP with captive portal deployments, each AP has its own internet connection, managed by routers I don't have access to. I can manage the APs through a cloud ...
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27 views

CIFS Input/Output error when executing set attributes

I have a CIFS share. It works perfectly with Windows, but if I want to create a file on the share, using Linux, it returns an I/O error stating that it could not set the attributes: $ touch a.txt ...
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1answer
42 views

Simulate 2 clusters in the same network

I have 4 pc´s and another pc, which will act as a proxy, all being in the same network: 172.16.96.0/20 . I can ping between each other. But, I want to separate them into two groups. That is: pc1 is ...
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46 views

Can I use a home-grade router to configure network for openstack cloud?

I'm trying to deploy a multi node openstack configuration using three physical nodes running SUSE Enterprise 11 SP3.(Controller, compute-1 and compute-2). I created a private network ...
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18 views

KVM Virtual Machines and Public IPs

I currently have some Virtual Machines on my business dedicated server using the KVM layer as apposed to Xen or other virtualization methods. I was wondering if I could get a "best practice" on ...
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18 views

Setting up routes for openstack

Im trying to make an openstack deployment following this guide OPenStack Juno Guide. I have a linux server which is configured as a Nat, with 2NIC's. I used this script on section 4.5 Nat.sh. My ...
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characteristics of interface type dummy [migrated]

I've configured an interface 'nonlocal' with type dummy ip link add nonlocal type dummy on that interface are some IPv6 addresses configured. Now an apache can start with some ip based vhosts on ...
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83 views

The same IP on multiple interfaces

Hello networking gurus, I've got a Linux (kernel 3.14) server which acts as a TFTP, NFS and HTTP server for a farm of consumer electronics devices (set-top boxes - STBs). The devices use TFTP to boot ...
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34 views

Strongswan IPSec + XL2TP connection not working

I am trying to set up a VPN (Strongswan + xl2tpd) between my desktop and a server in AWS both running Linux (Ubuntu) but I really am getting lost. I believe I have the IPSec part working but I am not ...
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61 views

OpenVPN sndbuf and rcvbuf

I would like to know what is the difference between the sndbuf and rcvbuf buffer used by OpenVPN and net.core.w/rmem_default or net.ipv4.tcp_r/wmem. What does OpenVPN do when some value a provided ...
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24 views

how to divert incoming all tcp packets at eth0 to socks proxy and to eth1 of same host?

I have a three ubuntu linux hosts. host 1,host 2 and host 3. I want to pass data from host 1 to host 3 via host 2. But specifically I want to pass all incoming traffic of host 2 to socks proxy then to ...
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87 views

Is there a way to limit bandwidth per ip using HTB + a CIDR range in Linux?

I can create rules to limit a entire subnet or to limit individual ip addresses with tc and htb. I am looking to use CIDR ranges to keep things somewhat elegant. The machines in question are all ...
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0answers
31 views

What builds /proc/net/bonding?

We're monitoring the network interfaces with Nagios/check_mk, which looks at /proc/net/bonding/bond0 to see the status of the interfaces. Unfortunately, we had an improper config and 2 NICs were in ...
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19 views

Not recognizing path to credentials on fstab

I'm trying to mount a remote filesystem with fstab, and using a credentials file to load the username and password, but for some reason I get this error message when I try to use # mount -a: mount ...
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ubuntu network settings equivalent in centos 7

I have in a ubuntu server an interface setup as the following (in /etc/network/interfaces) address xxx.xxx.xxx.xxx netmask 255.255.255.255 broadcast xxx.xxx.xxx.xxx post-up route add xxx.xxx.xxx.xxx ...
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24 views

NMAP port scanning - inconsistent results

I ran the same nmap commands subsequently, and got two sets of results. I know that there are three open ports, but on each run, only two are shown. Can anyone explain these results? ...
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1answer
32 views

Inconsistent nmap scan results

I'm working on a program that depends on scanning the local network for all connected devices and getting their MAC address. To do this, I'm running the following command: nmap -sn 10.0.0.* This ...
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39 views

OpenSuse: How to allow an outside network to access the local network?

I want to connect vlans of two separated networks I administer and it's almost complete, Allow me to describe the situation: Network A's firewall is a FortiGate 1000C and the vlan is 192.168.2.0/24 ...
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91 views

How to troubleshoot rx_missed_errors?

Migrating from old server to new one, after setting all services, I notice a big dropped rx packets in my NIC: $ ifconfig eth2 | grep 'RX.*drop' RX packets:2059646370 errors:0 ...
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23 views

Spurious retransmission, Dup ACK and HTTP 408

I have a server which serves as sms gateway (using kannel) and have multiple client connecting to it, but recently this one client with their particular IP said that they can't send to my server and ...
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27 views

Restricting ports to application / user

I'm currently working on a platform that will allow other users to run their applications on my platform. Though, we need to be able to restrict this application in terms of RAM, CPU usage, network ...
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29 views

Bandwidth Policing on Linux gateway - not QoS

I have a linux server providing NAT to a large subnet (/16) using iptables to-destination + multiple external ip's to survive port exhaustion. I've looked at using tc / htb such as here Limiting ...
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1answer
28 views

Time Between successive DNS queries.

Using a PC running Ubuntu 14.04. I'm testing web browsing using a very low speed and low data rate link. My system is congested with DNS queries (and other types of packets like TCP re-transmission). ...
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19 views

How can I bridge an HTTP server from an interface to another in Linux?

In a Linux server I have an HTTP server that's available at eth1 with ip1, and I want to make it available to the network in eth2 with ip2. How can I do this? Example: I have an http server on ...
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1answer
76 views

Linux: nslookup and dig resolve $HOSTNAME, but ping doesn't

In our private network we have a Consul service discovery server (10.241.232.14) that provides a DNS interface (port 8600). We would like to set our common DNS servers to forward some queries to the ...
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22 views

Gateway to internet on CentOS 6

I have 2 CentOS 6 linux servers say hostnames cent001 and cent002 cent001 has 2 Nic's 1 Bridged and 1 Nat cent001 is able to ping google server 8.8.8.8 with the help of bridged NIC cent002 has only ...
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64 views

dhclient vpn_tun0 causing internet disconnect after upgrade to ubuntu 15.04

A few weeks ago I installed softether vpnclient on my ubuntu 14.04 laptop and vpnserver on an ec2 instance. The server uses softether secureNAT and the softether dhcp server. My client produces an ...
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30 views

Get Original Destination Port From iptables

I would like to create a local server that acts as a proxy for all trafic, but how would I determan the original ports when using iptables to rederect the network traffic. I need this for when the ...
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2answers
80 views

Different subnet mask on router and DHCP server

ran into something funny today and am still scratching my head on why this happened. I was trying to increase the number of ip addresses available from my dhcp server by changing the netmask from /24 ...
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23 views

Problems with route table with two nics on different subnets

I have an Ubuntu server with two NICs on two different vlans. Both nics are able to reach the internet. The server is an Ubuntu MAAS machine and therefore has pxe and dhcp and such. The DHCP server ...
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2answers
78 views

How to get a client IP address from a specific network?

I have a condition to filtering IP address from client, and I just have their IP network like this 1.1.0.0/17. If some client from this network will be filtered as special user on my website. And I ...
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1answer
54 views

Trouble with network (ping, route, gateway)

I have a server running CentOS 7 and I connect to it by ssh. SSH takes a little bit to connect compared to the other server I have setup. This server has 2 ethernet ports (1 motherboard and 1 card). ...