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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CPU usage of server extremely low and webpage load time high?

On a weekday at a time where very few use the optimized website on the server, the time for the page to completely load excluding 3rd party advertisements is about 0.6 seconds to 1 second. Now when a ...
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2answers
160 views

Can't communicate with SMTP server from particular machine

Here is the situation: When I run the following on my local machine, the mail server responds: $ telnet mail.server.com 2525 Trying <mail.server.com IP>... Connected to mail.server.com. ...
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77 views

HowTo: OpenWRT routing/tunneling all traffic through an inline Snort sensor

I want all traffic that hits the OpenWRT router redirecting/ tunnelin through a dedicated Snort/Suricata machine, before it leaves the local network. The Snort/Suricata machine should act as an inline ...
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41 views

vyatta virtual router interface aliasing does not work

I am trying to create an alias on vyatta virtual router. But I do not seem to get it to work. In vyatta we have to just add another address to the interface to add an alias. But the interface is not ...
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28 views

IP hashing filter in traffic shaping

I am using a traffic shaping by IP hashing filter. I have Five networks /24 : 192.168.1.0/24, 192.168.2.0/24 .. 192.168.5.0/24 so i create a table with 5 cells and each cells has 256 cells. this is ...
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52 views

Strange issue with nginx proxy upstream and ssh port forwarding

We were using nginx legacy till now, but we upgraded our system to 1.6.2 recently. We have a port forwarding of ssh as well as load balanced nginx server for two separate internal servers. The ...
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1answer
92 views

cp -p will preserve times for some files but not all?

I have a source directory on a machine with a bunch of files, all with the same permissions, that I want to copy to another directory, that is mounted via SMB. [tmark@dexter JR09141045 ...
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14 views

Debian Linux Bridge Mode not forwarding

I am trying to bridge lan adaptor eth0 with the eth1 interface exposed by sierra wireless lte modem. When i create a bridge using the following commands brctl addbr br0 brctl addif br0 eth0 eth1 then ...
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20 views

Set up a GRE tunnel over multiple communication channels

I am in a situation where I would like to be able to set up a GRE tunnel running seamlessly over GPRS or Wifi in linux 2.6, preferring of course Wifi whenever available. So on one host I have two ...
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39 views

Ebtables to setup forwarding and nat

I would like to use ebtables to perform the following 2 things without using bridge-utils SCENARIO I: I would like to forward all the packets received from eth0 interface onto the eth1 interface. ...
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1answer
32 views

Make VNC available without opening non-ssh ports to the WAN

I have a local network consisting of a gateway router/firewall running dd-wrt, a machine running OS X called mac, and a Debian host named ssh-server. The firewall forwards port 22 to ssh-server. I ...
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43 views

Multicast works only in promiscuous mode

I'm trying to receive MPEG-TS over UDP multicast transport in Arch Linux. So when I run ffprobe -i udp://@224.1.1.240:6000 it hangs forever with no result. Then I run tcpdump and it shows no ...
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1answer
122 views

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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1answer
34 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
18 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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0answers
23 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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0answers
235 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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0answers
37 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
218 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
120 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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28 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
53 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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27 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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0answers
31 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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1answer
155 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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1answer
41 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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34 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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2answers
101 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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3answers
71 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
54 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
185 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
35 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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19 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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1answer
27 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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12 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
54 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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1answer
115 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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2answers
35 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
42 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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3answers
80 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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1answer
32 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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1answer
59 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 ...
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0answers
77 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 ...
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1answer
159 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 ...
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1answer
46 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 ...
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1answer
41 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 ...
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3answers
88 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 ...
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1answer
33 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 ...
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1answer
59 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 ...
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69 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, ...