Networking refers to the technologies and techniques that enable the interconnection of devices and applications allowing them to communicate electronically.

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Dropped packets in all Linux and Unix

I have a problem. I have a motherboard by Supermicro – X11SBA-LN4F. There are 4 ethernet ports. In the first port I connect to the internet. In the second port I connect to my local network. When, I ...
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22 views

limitation of 8 active port in LAG

i was going through Aggregation/EtherChannel topic and I got stuck in below statement "A dynamic LAG can have up to 16 ports of the same type but only 8 can be active at one time" any specific reason ...
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29 views

Linux machine gets different IP through and after installation

we have some automatic building of our building machines using packer (jessie, trusty, xenial, macos, ...) on separate network (VLAN on L3 switch which is used as default GW for the network). Till now,...
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20 views

Port forwarding from external providers in AWS VPC

I'm looking for general feedback regarding allowing external services access to your Amazon AWS VPC. I'm mostly wondering how other people go about doing this. If you're using an external service like ...
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1answer
23 views

netstat shows inequal amount of mutual connection between two hosts

I'm trying to investigate why the amounts of connections between two physical hosts 10.240.48.9 и 10.241.169.7 (CentOS 6) don't match each other (diagnosed from the each one respectively): On 10.241....
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9 views

How can I use instance discovery with openStack?

I'd like to use a service like TADDM to discover OpenStack instances. Unfortunately, this is tricky since OpenStack instances use private IPs. What are ways I can use to quickly distribute public IPs ...
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2answers
197 views

Printer not reachable in network

i've a low-cost printer Samsung i provided to configure in my network. i gave it a static IP and connected to my AP. i can ping (and use) the printer only if i'm connected to the same AP. why can't i ...
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60 views

Can't access particular website on Windows Server, but ping works [closed]

In my Windows Server hosted in AWS, I tried to access a particular site from Chrome/IE and both browsers returned - the site can't be reached/the server refused to connect. However, when I try to ping ...
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27 views

How to use nagios to monitor a pfServer server?

I have a pfSense server set up as firewall gateway for my lab lan and dmz. Now I installed Nagios monitoring manager on a Linux server in lan and want to add a host target for the pfSense firewall. ...
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40 views

public interface not listening by default centos 7

I have two NIC on my system with centos 7 as OS. One interface is public with ip 172.68.122.120 (em1) and second with ip 10.11.15.20 (p4p1). Now When I reboot my system, bydefault, public ip is not ...
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89 views

Access Point Iptable/Route rule for allowing device discovery? Devices can connect manually, but not automatically. Multicast/Upnp issue?

I setup a wireless access point on my server and for some reason, everything works but automatic discovery features. I can't see any other devices, upnp devives aren't discovered, and I think it's a ...
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66 views

Internal network DNS can't be configed to route domain.com to www.domain.com? [duplicate]

We host a domain on the internet that is accessible outside of our internal network using domain.com or www.domain.com, but is our actual internal network domain as well, but the external website is ...
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19 views

Network issue in Compute node instance

We have two servers with Openstack Essex. Controller node a. nova-compute, nova-network, nova-volume, nova-consoleauth, nova-cert, nova-scheduler installed Compute node a. nova-compute and nova-...
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59 views

“No route to host” when i do a telnet in azure

I have two VM's in azure with different public IP's and whose private IP's are : 10.10.1.9 10.10.1.6 When i do a telnet with following command from the server 10.10.1.6, i get the a error: telnet ...
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65 views

Renewing public dynamic IP via Powershell ?- Azure Resource Manager

i need your help! I'm trying to renew a dynamic IP assigned to a VM, but i want to figure it out if there's some possibility to accomplish this via powershell cmdlets without being in the need of ...
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1answer
25 views

Basic Vlan questions

I've been "awarded" with IT infrastructure manager possition as I'm the "good with computers" guy in my small office. Nedless to say they have made a huge mistake, I have no clue.... I'd like to ask ...
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52 views

Azure vpn is establish but causing delay or no traffic sometimes

We are trying to establish VPN Hillstone FW (device) with Azure. VPN details are: VPN type: Policy based Gateway Subnet: 192.168.50.10/29 default subnet: 192.168.50.0/29 VM inet Address: 192.168.50....
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139 views

Forward traffic between VLANs with iptables

We're having the following 4 VLANs on my network, connected to an Ubuntu Linux box with DHCP. This Linux should act as the L3 router as well. VLAN 10 on interface eth1.10 with subnet 10.10.10.0/24 ...
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2answers
53 views

CentOS 6.7 vm static external IP setup issue

I have a new vm setup and have it setup like my CentOS 5.5 vm on OSX. It is a strange setup since we used Comcast Gateway as the router, and I really don't want to change that since we're using Mac, ...
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1answer
124 views

Any tool for forking/teeing/sharing a TCP connection to the remote server? [closed]

Could down voter please post your reason, as it's not obvious to me? Here's my problem. I'm building an automation program that talks to a remote server (think of it as a chat server or MUD game ...
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20 views

Firewall-Rules on Proxmox-Node cause VPS to be offline

I'm using proxmox to virtualize some small machines based on KVM. To do so I created the following network-config on the KVM-VPS: # This file describes the network interfaces available on your ...
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1answer
88 views

configure docker network bridge IP for multiple IP alias

I got a Ubuntu host with multiple IP address aliases and I want to expose the ports from docker containers connected to one docker network bridge to a specific IP address of the host and the ports ...
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16 views

What is the default value for TCP accept queue length on Linux?

I have read this article but it doesn't mention where the default accept queue length can be found (it does mention tcp_max_syn_backlog though, but it's different). I'm working on a Java 8 project ...
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27 views

Large payload - connection get's Hung with CLOSE_WAIT or LAST_ACK state

We have a webservice client which posts data to a 3rd party Webservice. We are having an issue when the payload is a bit large (Around 600KB) xml. Once we pay the process hangs forever. The Netstat -...
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64 views

Multiple Gateways for Single Subnet

Right, this might be a long one, so bare with me... I have 2 machines, lets call them local1 and cloud1. local1 has 3 Nics: 2 connected directly to cable modems with public IPS (call them eth0 and ...
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83 views

proFTPD unable to connect after update ECONNREFUSED

I am working on Debian 8 - ran a series of automated system updates and now I am unable to connect to my local server running proFTPD. I have made no changes to the client attempting to connect to ...
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18 views

Infinite loop of RST/ACK and ACK

I have web servers (Apache-Tomcat) at IDC to serve https requests from Android and iOS clients. Suddenly I noticed traffic to web servers was dramatically increased (10Mbps to 80Mbps). So I tried to ...
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36 views

LXC containers cannot connect outside of VM

I have two CentOS 7 LXC containers on a RHEL 7.2 VM using virbr0 as a virtual bridge. Originally, container1 could connect out and do e.g. yum installations, but after I created container2, neither ...
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1answer
61 views

Possible to force TCP window scaling to a higher value?

Is it possible to increase the TCP window scaling factor on Linux (CentOS 7.2)? I have a long fat network (100 Mbps) from London to Chicago and I'm getting 16 Mbps throughput in TCP on an sftp from a ...
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1answer
90 views

HP ProLiant BL460C Gen9 - NICs

Is there a way to get more than 4 physical NICs (4 active/4 standby) on an HP BL460c Gen9 server WITHOUT using mezzanine cards and extra VCMs? EDIT for more information: I have two c7000 enclosures. ...
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21 views

Using the host inet address to connect containers

Running an Ubuntu 16.04 server as a docker host. One of the services I start has the following run script. #!/bin/bash # retrieving the inet address INET=`LANG=c ifconfig | grep -B1 "inet addr" | ...
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57 views

How can I connect a group of vms in Azure?

I have a number of Azure Linux VMs. I am able to ssh into all of them using the public azure connection info, however I am not able to ssh from one vm into another vm using the private info. I have ...
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104 views

Slow file transfer speeds

I have a server that is running Ubuntu Server 14.04LTS and I am currently experiencing slow network transfer speeds. This server had been running without issue now for about 2 years and suddenly I am ...
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73 views

libvirt: set hostname using dhcp in virtual network

I've configured a host-only (aka private) network for a group of VMs on a CentOS 7 host. I've created static leases in the DHCP section for the virtual network. The IP address is getting set ...
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97 views

IPv6 not working

I'm unsure as to why this is happening... anyway, let me start from the beginning The Setup 1 * Dedicated server with a /29 IPv4 and /48 IPv6 (from Nocix (DataShack)) 1 * CentOS 7 KVM host 1 * ...
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1answer
190 views

Tune windows for high latency/high bandwidth tcp transfers

How can I speed up my Windows 7 tcp file transfers over a 100 mbps link between Chicago and London? Right now, I am transferring two 4GB files in two sftp sessions. Each file transfer is running at a ...
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2answers
61 views

Can't ping between two VMs

I have two VMs that, up until yesterday, have been able to talk to each other just fine. Now they don't. I've been trying to get this fixed for several hours now, but haven't been able to figure ...
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29 views

PPTPD VPN Can't connect to the internet

I'm running a Ubuntu 16.04 Server on a VMWare ESXI Server with its own public IP, I have setup a pptpd vpn server which works but only with connected devices. I can't connect to the internet with it ...
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1answer
54 views

Network maps, best admin practises and how them saved your ass?

I am reviewing the security of a (quite large) network. There are a some thousands switches, several hundred routers, several hundred access points, tenths of FW, IPS, and so on. PCs and servers are ...
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78 views

How to secure dual-homed Windows Servers that are connected to the internet

We have two machines running windows server 2012. Both have one NIC port connected to the public internet and another NIC port connected to a switch with internal IPs (192.168...). What is the most ...
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3answers
57 views

VisualSVN server visible on internet, but not all subcommands work on client

So my boss is a nice guy who's open to trying new ideas, and I talked him into letting me start new projects on svn (instead of an older version control system). At this time, we've realized that it's ...
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45 views

Can I create an Ad-Hoc network between NAT virtual machines and computers/virtual-machines external to host? [closed]

I want to create a network between virtual machines on my laptop which are running Windows Server and other virtual machines in another laptop that will be running Windows Server as well without using ...
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1answer
233 views

Huge performance penalty in gbit link with ip forwarding / masquerade through clear VPN tunnel

I have a problem with IP forwarding between my home computer and a remote server (from online.net). My home connection is a 1 Gbit/s FTTH and the remote server has a 2.5 Gbit/s bandwidth. The context ...
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32 views

Set-up VPN using DD-WRT router

I'm trying to set-up a VPN with a DD-WRT router in a Windows 2012 environment. I followed the steps from DD-WRT wiki 2, but I can't manage a connection. Firmware: DD-WRT v3.0-r28788 std (01/13/16) ...
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67 views

duplex affecting bandwidth test, router--switch--NIC

Netgear FVS336gv3 router, 50x50 dedicated fiber. ISP instructed us to set WAN port speed to 100mbps full duplex; done. Router connected to Netgear GS748T 48-port switch. GS748T port set to "auto" ...
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GNS3 - Connecting Emulalated IOS to TWO PHYSICAL networks

I have a CISCO c3725 router on GNS3 connected to two different and separate unique LANs via the CLOUD/HOST icon, attaching each of the virtual CISCO c3725 to my computer's physical NIC (NIC 1 and NI2.)...
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51 views

linux veth use existing peer interface

I have a sit tunnel interface which I want to transparently connect with one end of a veth pair so that everything that drops out of the tunnel interface flows through the veth interface and vice ...
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3answers
48 views

Override AWS Auto-assign Public IP settings after instance launch

There is a limit to 5 public IP addresses (Elastic IPs) for each AWS Account and I have reached such limit. Now I have many EC2 instances created without the "Auto-assign Public IP" attribute, which ...
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41 views

Ubuntu 16.04 LXD No any communication between guests and master

Welcome. I had a little problem with my LXD server. On my master I have some guests systems (ubuntu 16.04 image), all of them are bridged to master and are in my local subnet at home, and have an ...
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25 views

Can't reach centos server after “Multicast listener report” IPV6

I ran into a problem that occurs only on a few servers. Every 5-6 minutes I lose connection to the server, and it get backs after a few minutes. In most cases it's a VM that is not reachable while ...