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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Centos 6 Require Password to Enable NIC

We are using a dedicated NIC as a port forward target to allow support access to port 22 on a CentOS 6 machine. I would like to prevent the NIC from being enabled without a password. I know I could ...
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21 views

How to divert all traffic to our local port 8080 or a external IP:port

We have a VPN server on Linux, users connect to that server and browse the web. What we want is to setup a default webpage, say we have Apache running on port 8080. So by default we want all the ...
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Subnet cannot access internet on CentOS 7 with VMWare

Using VMWare Pro, I have two nodes with Centos 7 installed - one connected to my router with two network cards. The other is another node I want to connect to the internet on a different subnet. It ...
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9 views

PostgreSQL not listening on local eth1 after reboot

I have a server with 2 networking interfaces - global on eth0, and local on eth1 with IP like 10.181.xx.xx. Running Ubuntu 16.04. I set up PostgreSQL to listen on this local address, so another ...
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4answers
38 views

How to get list of all the hostname / DNS of the Linux box

I have a Linux box and I know I can get the list of IP addresses assigned to that box using following command /sbin/ifconfig -a but how to I get the list of hostnames / DNS for that Linux box using ...
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19 views

How to figure out why my NAT-box sends TCP RST packets?

TL;DR: I see that an ubuntu (which I have an absolute control of) host sends a packet under certain circumstances. How to find the application/kernel module responsible for that packet? I am ...
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22 views

dhcp server gives “no free leases” error although there should be available IPs

We have a small HPC cluster of about 40 machines running Rocks Linux Distro 6.2 (based on Centos 6.6). I have been trying to add 6 more machines to the system in the last few days. The first 3 were ...
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25 views

Difference between vlan and ip aliasing from user perspective

I was reading information about vlanand how to manage it on GNU/Linux. Whenever I needed to add a second network to the same physical NIC I would do ifconfig eth0:test 192.168.66.1 and with it I ...
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Automatically acquire IPV6 address in CentOS 6

The network has fixed IPv4 address, and automatic acquired IPv6 address. Does anyone have an idea how to setup? Thanks a lot! I didn't use NetworkManager. The following is my setting, but it does not ...
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1answer
2k views

Adding subnet to a vsphere with single vcenter and esxi host

Let me start of by saying that I do not specialize in networking, I am in the process of adding additional VMs to a testing environment and wanted some recommendations. In this case I am running a ...
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1answer
18 views

Can't access apache webserver remotely after connecting to VPN

I have an apache webserver installed on my pc whcih works as expected untill I connect to my VPN service provider (Private Internet Access) using their software. Once connected I'm no longer able to ...
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+100

CentOS 7 connectivity issues

I have a second CentOS 7 box that's having a lot of trouble connecting. Basically, we were running WHMCS, but a domain lookup kept failing. So the issue is IPv6 connectivity. [root@da01 ~]# yum ...
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How to setup VM network such that they all have different public IP addresses

For example, in Azure or Digital Ocean or EC2, we have an option of creating unlimited number of virtual machines. How does each of these VMs come to have different public IP addresses. More ...
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15 views

How to use two NICs [1onboard and 1 lan card] of my server [Ubuntu]? [on hold]

Good day, my scenario is I want to configure both of my NIC so that 2 different networks [192.168.4.2/200 and 192.168.1.2/200] can access my Web server. I jut want to know if it is possible? and How? ...
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1answer
389 views

Using my IPs on OVH server via GRE

I can't route my IPs into a OVH server, can you help me to find the problem? Mikrotik GRE IP: 192.168.55.10 OVH Server GRE IP: 192.168.55.20 GRE iface name: ali1_fr1-ovz1 IP to route from Mikrotik to ...
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0answers
19 views

How to upgrade Ubuntu to 16.04 LTS and not lose network access

When I upgraded one of my servers to 16.04 LTS I had to adjust network configuration (I use interfaces file) and use the new network interface name. I was lucky that the server runs in a VM and I ...
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4answers
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How to see on Linux what network interface and source IP address is used for a route to a specific destination host?

If I have multiple network interfaces (here: 2) on a Linux machine (here: Debian Lenny). How do I see, over what network interface (NIC) a route to a specific destination host is going and what source ...
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1answer
23 views

DH GEX group out of range

I'm having a sudden issue SSHing into my server: ssh -v --@-- OpenSSH_7.2p2 Ubuntu-4ubuntu1, OpenSSL 1.0.2g-fips 1 Mar 2016 debug1: Reading configuration data /home/paul/.ssh/config debug1: Reading ...
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17 views

How can I make Kickstart chose which build to run, depending on the subnet of the client?

I have 2 possible subnets that systems could be built in using Kickstart, with the subnet of the client directing which build should occur. How could I go about this? I have tried the following %...
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2answers
4k 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
17 views

TCP retransmission delays - lost acks

Maybe somebody will be able to help me out with this. I'm trying to find out if there is anything that can be optimized server-side to reduce delays in case of packet loss. Environment: Windows 2012 ...
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1answer
32 views

Close all _existing_ TCP connections on some ports using IPTables?

Say I have a quick network partition test that I'd like to run, like disconnecting two halves of a ReDiS cluster from each other, and I want to use IPTables to temporarily disconnect one group of ...
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13 views

Pervent connman disable wired interface

I'm running application over Centos 7 using Connman to manage connectivity. I have one issue working in the following scenario: Wired connection is enabled and online, have inet connection in this ...
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1answer
48 views

cannot use localhost but 127.0.0.1 works

My usecase is that I manage remote computers using reverse SSH tunneling. This works great as our customer enable the tunnel and I can then log on using it. However, on one machine the tunneling ...
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Configure network card without knowing its name [migrated]

I have a domestic headless server that boots from (and has the root filesystem in) a removable USB stick. I install it from my laptop (following this nice checklist) and edit the configuration files ...
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33 views

How can i set my new ip adress? [Debian / Ubuntu] [closed]

I have my own VPS at OVH and it comes with a default ip address in France. So for geolocation needs, i bought one for in the UK. Now i have Ubuntu server 16.40 running, and i want to set my newly ...
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2answers
59 views

Linux block outgoing traffic to a specific ip without iptables

I basically need to run the following iptables -A OUTPUT -d 169.254.169.254 -j DROP except I cannot use iptables because the program is running in a docker container and I cannot use the --privileged ...
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0answers
503 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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1answer
15 views

KVM - Adding public IP over bridge

I am working on setting up a KVM environment and normally I just take it for granted that the networking has been set up. I am running into difficulty getting the public IPs accessible from the VMs. ...
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9 views

Sar command “sar -n EDEV -f /var/log/sa/sa16 -s 11:00:00 -e 15:00:00”

sar -n EDEV -f /var/log/sa/sa16 -s 11:00:00 -e 15:00:00 I am using above command on Red Hat Enterprise Linux Server release 5.9, and below is the output to that:(Dev error form 11 am to 3 pm). I have ...
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27 views

Debugging dropped UDP messages on Linux

Here's my setup: I have 1 host that has a 1 Gbit Ethernet connection and 2 hosts with 100 mbit connections (connected to the 1Gbit host through different switches). In a test, I send 1000 1kb ...
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Iptables u32 matching nat

I'm currently setting up IPtables to redirect certain UDP payloads to my application. Here is an example of what I have working so far: iptables -t nat -I PREROUTING -p udp -d {IPDST} --dport 27055 -...
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20 views

Same mac addresses discovered in VM for bridges on host machine

I have two bridges on host machine, named br0 and br1 (having different mac addresses). A VM is connected by bridged networking through br0. Now VM is able to ping br0, which is normal. But it is also ...
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6 views

Username lookup for TCP Wrapper

I would like to ask people in this community regarding to TCP Wrapper. My OS environment is below. [root@server1 ~]# cat /etc/redhat-release Red Hat Enterprise Linux Server release 7.2 (Maipo) [...
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Inherited debian cluster nightmare

Hi and thanks in advance. So my research group at my university inherited an 8 node cluster. Me being the only member who is Linux savvy was given the task of managing it. So to start I'll describe ...
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2answers
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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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41 views

hostapd Wired 802.1x with Bridge

I've got a PCEngines APU running Debian Jessie. I'm trying to configure hostapd to perform wired 802.1x authentication against a remote domain controller running NPS on 2008 R2. I would like 2 of it'...
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78 views

Pacemaker: How to configure default gateway for virtual IP?

I have three nodes and three virtual IP addresses in the same subnet. It doesn't matter which address is assigned to which node. The IPs are public addresses. The nodes are load balancers that ...
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1answer
20 views

Cacti generate old graph

I have a cacti system (Version 0.8.8b). The cacti system has been running for a year. I would like to generate retroactive daily graphs, because cacti can't show the old daily graphs. How to ...
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2answers
41 views

Load Balancing & High Availability Network Limitations

I'm in the process of coming up with a highly available Apache / MySql group of virtual servers using HAProxy Reverse Proxy & Keepalive. I'm aware that I'm going to be using a floating public ip, ...
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2answers
1k views

What is causing the famous “broken pipe” when I use tmux inside an SSH session?

Scenario1: I SSH from my employer (OSX Yosemite SSH client) to my home server (Debian stable) and (re)connect to a tmux session. If I leave the terminal inactive for a while (~20minutes), it seems ...
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35 views

static network setup still using DHCP

I'm configuring an Ubuntu 14.04LTS server on our internal network. Everything works and runs as expected. Its assigned a static IP, here's /etc/network/interfaces # The loopback network interface ...
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22 views

vnstat and dstat report different totals

I'm trying to monitor bandwidth going through one of my interfaces, and I've discovered that dstat and vnstat both seem to report different rates... vnstat: [root@... ~]# vnstat -i eth8 -l ...
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42 views

How to create a HTTPS Proxy?

I have to setup access to a remote API service in which requests are IP-Whitelisted. The problem I have is that my web-nodes are in the cloud and their IP addresses often change. Therefore I want to ...
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2answers
1k 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 properly....
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4k 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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2answers
61 views

Installing Mellanox ConnectX-2 10gbe PCIe Card on Centos 6

I just installed a Mellanox ConnectX-2 10gbe PCIe x8 Card into my server running CentOS 6.7. On boot, dmesg shows the mlx4_core driver being loaded automatically however I see no eth1 device ...
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How does AWS configure the 169.254.169.254 address on an instance?

AWS uses 169.254.169.254 as a link local address, which you can use to pull meta data about the instance, ie: curl http://169.254.169.254/latest/meta-data/ How/where is this IP configured on the ...
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1answer
35 views

IP Range - Subnet network configuration on CentOS 6.4

I have problems to configure an subnet /25 on an vps with CentOs 6.4 have tried different version. The original eth0 settings are: DEVICE=eth0 #HWADDR=de:8f:24:e9:7b:04 TYPE=Ethernet UUID=64e110dd-...
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3k views

How to configure VXLAN over linux bridge?

I am using Ubuntu 14.04 which support VXLAN configuration. Currently I can add a VXLAN interface such that: vagrant@ubuntu:~$ sudo ip link add vxlan1 type vxlan id 1 group 239.1.1.2 vagrant@ubuntu:~$ ...