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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Proxmox: 1 NIC, 1 Public IP, unable to get WAN interface working in VMs

I have a computer running Proxmox, and it has 1 single NIC that is directly connected to internet and has a single public IP. Then, I have different VMs (KVM) running and one of them is pfSense. What ...
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61 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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1answer
26 views

1-dhcp server for 2 separate network

Debian Server Setup (wheezy) 1 - eth0 - Connected to INTERNET 1 - eth1 - LAN 1 (Network 1 : 192.168.100.0/24) 1 - wlan0 - Access Point (Network 2 : 192.168.200.0/24) /etc/network/interfaces auto ...
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2answers
12 views

Make some route info persistent on RHEL

I would like to make the following route info persistent. I know how to do it for the default, but how about this line: 10.27.74.0 * 255.255.255.0 U 0 0 0 eth0 ...
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12 views

Process-wide VPN connection via openconnect

I'm using openconnect to connect to a remote endpoint and SSH onto the machine inside the remote network. The problem is, when I do create the connection, the machine I do it on is unresponsive for ...
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18 views

Siege: descriptor table full sock.c:119: Too many open files

I am trying to make a stress test in my own server using siege with the following command: $ siege -c 500 myweb.com/somefile.php But I get this error: [error] descriptor table full sock.c:119: Too ...
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1answer
855 views

WMI: wmic linux agent query error: NTSTATUS: NT_STATUS_ACCESS_DENIED

Myself new to wmic and keep trying for a long time with default agent query approach. wmic is linux based WMI tool to talk to windows WMI agent. While trying to fetch data with wmic from nt(win7 with ...
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1answer
19 views

what could cause a not so busy redis server to close connection?

We have 17k tcp connection in CLOSING state on redis server. My understanding is that only client would initiate closing a connection, not from a redis server. So I should see 0 connection in CLOSING ...
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13 views

Openswan tunnel established; but have access problems

I am working on connecting two office using OpenSwan IPsec VPN. I have successfully established the tunnel, but ran into strange problems: Let's say subnetA(192.168.1.x/24) and ...
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1answer
913 views

Network aliases on boot on Fedora 17

We have a fedora server(Fedora release 17 (Beefy Miracle)) with a few aliases on the main NIC that don't get setup during boot. Here's my config: # cat /etc/sysconfig/network-scripts/ifcfg-em1* ...
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63 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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14 views

Route 2 external IP ranges using pfSense

I have pfSense running on some hardware routing my /27 block of IP addresses assigned by my ISP. I asked for and got another /26 block that I want to send all of the block to a single server (it will ...
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1answer
47 views

How would traffic be routed with this routing table

I ran across two entries in a linux routing table that both have the same destination, but have different gateways. How would this traffic be routed? I've been searching around online for additional ...
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1answer
170 views

Nagios alert based on scheduled MySQL queries results

I have installed Nagios 4.0 on my Ubuntu 14.0 and i want a plugin to alert me based on daily scheduled MySql queries .. if the result of ( select count(*) from tableName > 10 ) raise a critical ...
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1answer
28 views

zabbix network interface app shows no items for CentOS VM

I'm using a Ubuntu VM as Zabbix server and Zabbix agent1, and a CentOS VM as Zabbix agent 2. And when I look at the overview at the property "Incoming network traffic on eth0", only Zabbix agent1 (the ...
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20 views

How does tcp communicate back to the appication? [closed]

Are there standard sytem calls to send data to TCP? And back? How does TCP tell the application to send more or less? We have an application that periodically fails to transmit a 600 MB of database ...
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9 views

source based routing policy use ip route not works on my vm

I have an vm created with vmware. an installed centos 7 as os. the kernel is 3.x. now , my system have to network interface. and I want connect them to the same network. forexample : ...
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1answer
2k views

Error while bringing up eth1

I'm getting this error while bringing up my network card: (process:2550): WARNING **: _nm_object_get_property: Error getting 'State' for /org/freedesktop/NetworkManager/ActiveConnection/3: (19) ...
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24 views

Purpose of sysctrl tcp timeout unack field

Could some one let me know the purpose of sysctrl tcp timeout unack? If i modify this value from 300 t0 400, what will be the impact. /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_unacknowledged ...
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17 views

dhcp relay with failover to local service

I'd like to set up a dhcp server which normally relays to a central site, but has a pool of addresses to hand out if the link to the central site goes down. I'm using isc dhcp server on Debian, but ...
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37 views

configure a dhcp server to serve two different scope on the same subnet with multiple interfaces

Ok, so here I am with a pretty complicated problem on a Debian Wheezy server I have three interfaces : eth0, eth1 and wlan0 on a single server, eth0 will act as a gateway for eth1 and wlan0, I have a ...
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22 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 ...
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5answers
6k views

What network loads require NIC polling vs interrupts?

Does anyone have some data or basic calculations that can answer when frame coalescing (NAPI) is required and when a single interrupt per frame is sufficient? My hardware: IBM BladeServer HS22, ...
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1answer
9k views

NAPI vs Adaptive Interrupts

Could anyone please explain how two following technologies are used to mitigate interrupt overhead under high networking load? Adaptive-rx/Adaptive-tx, and NAPI; I would appreciate an answer that ...
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27 views

Trying to create a NAT with virtual Ethernet using IPTables

I have a separate namespace running on my server and I want to create a NAT that will enable Internet connectivity in this namespace. I specifically want to do this so that certain inbound ports are ...
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19 views

IPTables Quota Limiting and Redirect

I am currently working on a quota limitation for a wireless captive portal based on iptables. With the following ruleset all new connections get redirected to the login page after the quota is ...
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2answers
58 views

How are packets routed from my VirtualBox Virtual Machine to my local host OS environment? [closed]

I have a basic question I do not understand regarding the IP given to a Virtual Machine running on my laptop. I use boot2docker (basically, it creates a VirtualBox Virtual Machine to have access to ...
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1answer
2k views

eth0 NIC Link is Down repeating message in kernel log

I've noticed since few days ago that same repeating kind of messages occurs and I positively can say that nothing was intentionally changed (installed/uninstalled) in that period. here's sample of ...
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3answers
33 views

“Bad argument 'NEW'” when configuring iptables

I am getting the following error when configuring iptables on a Debian 7.6 server to log new TCP connections: Bad argument `NEW' Error occurred at line: ## The line throwing the error is formatted ...
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2answers
33 views

Excluding some network services from VPN

My local linux server is connected to the internet via router. Router (192.168.0.1) does NAT from ISP assigned IP address (which changes from time to time) to server's local IP (192.168.0.102). When ...
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1answer
48 views

Networking in Linux KVM

I want to know if there is any 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 ...
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3 views

Bridging multiple networks with a tinc vpn in virtualbox, won't forward packets properly [migrated]

I set up a network with some VMs in VirtualBox. It consists of: 1. The host, OS X. It is connected to the Arch VM described in 3. via a host-only adapter. OS X has the IP 172.31.2.100/16. 2. ...
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1answer
229 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 ...
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2answers
901 views

VMWare and Turnkey Linux appliance can't access network

I have a VMWare ESXi cluster running many Windows and Linux VMs perfectly. I have installed the Turnkey Linux Redmine appliance, and am having a lot of trouble getting the networking to work ...
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1answer
62 views

I cannot connect to OpenSSH server running on Ubuntu server from Git bash running Windows, through Cyberoam firewall in network

Situation: I am trying to connect from OpenSSH client inbuilt with Git Bash running on Windows 7 professional x64 to OpenSSH server that runs on Ubuntu Server LTS 14 x64. Both of which are over the ...
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1answer
964 views

Infiniband port status UP but can't open UMAD port ((null):0)

My system has 2 infiniband devices, one of which has both the ports up. $> ibstatus Infiniband device 'mlx4_0' port 1 status: default gid: fe80:0000:0000:0000:0002:c903:000f:0a9f ...
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1answer
19 views

Assigning a public IP to a Xen Guest machine

On my CentOS server (dom0) I have 4 Ip addresses: eth1 - 56.x.x.100 eth1:1 - 56.x.x.101 eth1:2 - 56.x.x.102 eth1:3 - 56.x.x.103 How can I map eth1:1 (etc) to one of my guest machine? Currently ...
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14 views

Bridging Interfaces and limiting Egress of children

HISTORY: First let me explain what I want to do: I want to setup a development / staging environment based on LXC so our developers can rapidly deploy and tear down VMs. We have a single public ...
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24 views

how to change MTU inside docker container which is running with ubuntu 14.04 and also on host machine with ubuntu 14.04?

I want to change MTU(Maximum Transmission Unit) inside docker which is running on ubuntu 14.04. also docker container running with ubuntu 14.04. The problem is that its docker0 interface on host os ...
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0answers
25 views

Tomcat 7 inaccessible on digital ocean

So, I'm trying to get Tomcat to work on Digital Ocean. The server starts up without errors, but it's inaccessible both locally and remotely. It hangs when I try to access it. However, it does work ...
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1answer
26 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 ...
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3answers
2k views

How can I achieve OpenVPN client routing without NAT on Linode

I've set up an OpenVPN network, and it is working properly in the sense that I can access the inner/LAN machines from the remote client. However, my problem is that all traffic from the remote ...
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1answer
23 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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11 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: ...
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1answer
40 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 ...
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1answer
47 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 ...
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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 ...
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2answers
33 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 ...
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2answers
36 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 ...
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1answer
90 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 ...