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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Debian - Routing multiple virtual interfaces

I've a Debian computer with multiple external IPs (7 in total), each IP has its own virtual interface (eth0:1,eth0:2, etc...) I would like to know: how can I configure routing so each time I ssh to a ...
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3answers
181 views

Iptables rules with ! character

I have entered iptables rules to log a specific connection on our server, but it doesn't seem to be working as I want it to. Here are the rules: 1 LOG tcp -- !10.51.0.0/16 ...
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31 views

Routing private IPv4 addresses internally

I have the following set-up involving two KVM hosts and numerous virtual machine guests on each. The guests communicate to each other on both hosts via [192.168.216.0/24]. [192.168.216.42] is ...
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2answers
53 views

arp table entry outside configured network

Can someone tell me why do I have arp table entry outside interface network? Server has 2 interfaces, both on the same network: eth0 10.10.34.146/22 eth1 10.10.33.188/22 ip route default via ...
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2answers
71 views

Http Requests: how to identify a machine using multiple IP addresses

I have an http server. Is it possible to identify a machine, which is making http requests to my http server using different IP addresses? In other words, is it possible to identify a machine, by ...
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1answer
75 views

Cannot Access remote CentOS machine using VNC

I am trying to connect to a remote CentOs machine through VNC to get a graphical display. I have followed the steps mentioned in https://www.howtoforge.com/vnc-server-installation-centos-6.5 to ...
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2answers
155 views

Linux Red-hat 6 Network manger interface priority

I have a question regarding RedHat 6 Enterprise Network Manager (NM): My Linux is connected to two network interfaces. 1 – eth0: Normal Ethernet which is connected to the company LAN 2 – eth1: An ...
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32 views

Ubuntu DHCP-RELAY Error

I have a Ubuntu 14.04 server running as a router (4 NICs with IP forwarding turned on). The routing/forwarding component is working fine. However, I now wish to implement a DHCP-Relay/IP helper so I ...
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32 views

iptables, after specifying an interface to drop traffic it drops all traffic of all interfaces

We have currently the situation that one interface (eth0) is linked to the internet. and we 2 other devices (eth1/eth2) for management purposes. Now the idea is to block off eth0 completely from the ...
2
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1answer
64 views

Virtual interfaces with different MAC addresses

I try to figure out how to set up two logical network interfaces (at one physical interface) with separate MAC addresses on a Linux machine. My first attempt was to use macvlan which seemed to work ...
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1answer
90 views

Adding a VLAN to Multiple Aliased (Virtual) Interfaces

I have a server running centOS 4.6 with 4 NIC ports. I successfully set up 2 ports with 32 virtual interfaces to handle my VLAN-untagged connections and have no issues with that side of things. ...
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4answers
92 views

Linux-Networking: How do I get routing to work with two network interfaces on the same subnet? [closed]

I have a Ubuntu machine with ip_forwarding enabled. iptables forwards too. I have 3 network cards. eth0 - internet eth1 - client1 eth2 - client2 I want eth1 and eth2 to be on the same subnet, ...
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1answer
119 views

how to change the ftp passive mode ip address for haproxy work as reserve proxy?

I have an ftp server in LAN, address is 192.168.1.11 I used haproxy is because lots of other service need it I put haproxy on my 192.168.1.1 the same machine of our soft-route(ubuntu 14.04) My ...
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1answer
73 views

Why is port 443 (but not port 80) being exposed to nmap when iptables is configured to drop the traffic?

A Debian box is running web services on ports 80 and 443 and iptables is configured to allow web traffic only from white listed ip addresses. A second Debian box (that is not white listed) is using ...
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1answer
61 views

IP Forwarding Issue

This is my first post, so thanks in advance for y'all's help. I'll try to keep the background succinct and relevant. I am running a server on centOS 4.6 for network client testing. I have the local ...
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108 views

How to deploy single OpenVPN server instance with multiple unique “--config server*.conf” profiles?

How to deploy Single OpenVPN server instance with Multiple unique --config server*.conf profiles as service start|restart parameter ? Would you please share any tips to run one single Openvpn server ...
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2answers
138 views

How to configure network interfaces for three NIC cards all on three different subnets

I am setting up a cloud environment on Ubuntu and I am running into an interesting problem. Out of the box Ubuntu (all linux really) doesn't allow you to specify more than one gateway in ...
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1answer
173 views

Reverse zone not working with BIND9

I'm trying to configure a DNS server in UBUNTU 12.04 with BIND9 service.I'm able to successfully configure the same and the when I'm executing nslookup command it works well.However,the host command ...
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0answers
49 views

Setting up LDAP to authenticate users in data center

I'm a newbie to linux and networking. Somehow I'm assigned to research the tasks of setting up the authentication for users to login in from local office to data center. Here's the hypothetical ...
2
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0answers
81 views

When is route lookup performed when a packet flows through iptables?

Iptables is often illustrated using diagram I fail to understand when route lookup (routing tables) is performed: inside the "Routing Decision" grey boxes? If so, does it mean a packet is routed ...
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2answers
49 views

How to use a server as a “tunnel” in between the clients and the router, in a small network?

Consider a small network with 1 router (192.168.1.1) and clients (192.168.1.x). The router (OpenWRT) provides Ethernet LAN and WiFi for the clients, to connect to the Internet. Now, I want to use a ...
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0answers
47 views

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
265 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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116 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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1answer
79 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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32 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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0answers
81 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 ...
4
votes
1answer
252 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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32 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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0answers
47 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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78 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
58 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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72 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
301 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
38 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
23 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
31 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 ...
2
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1answer
732 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
62 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 ...
5
votes
1answer
326 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 ...
0
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1answer
312 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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64 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
58 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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0answers
34 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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54 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 ...
0
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1answer
495 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
113 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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42 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
191 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
129 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 ...