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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TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
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11 views

Policy routing local user's traffic down a tunnel

I've got a Linux based Firewall/Router running iptables and SNAT for traffic passing through it to the Internet via a single uplink - This is working fine. There is also a small number of applications ...
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13 views

Siege - running a stress test benchmark

I need to do a benchmark test of a HTTPS server using Siege, to see how it behaves under massive load. I'm initiating tests from another machine which is quite powerful and it is connected to the same ...
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2answers
681 views

Service networking restart not working on ubuntu

This one has been cracking my head for quite a bit and I can't seem to find a decent answer for it, hoping you guys can shed some light to it... # Loopback interface: auto lo iface lo inet loopback ...
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2answers
27 views

Allow connection only from 2 ips [on hold]

I need to block all connection on port 30000. I alredy did that , with command like that iptables -I INPUT ! -s IP_HERE -p tcp --dport 30001 -j DROP but now i need 2 ips , how i could do that? ...
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0answers
14 views

What it takes for an openstack instance to connect to internet

I'm running a two node openstack cloud with single NIC using nova-network, Everything seems fine but when it comes to networking there are many problems and I think thats due to having only one NIC on ...
0
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1answer
29 views

KVM Ubuntu Guest cannot connect to the internet on bridged networking

I have Ubuntu 14.04 (64 bits) + KVM Host with 2 NICs: - eth0 connected to the "public" network - eth1 connected to the br0 bridge with a private ip address range From Host I can access internet, ...
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2answers
23 views

When a socket switch to TIME_WAIT state, why I can't see its inode number?

I'm developing a program in python that parses /proc/net/tcp informations, but unfortunately, while I was doing this, I saw a strange thing. Practically, when a socket change in TIME_WAIT state, ...
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8 views

Opening a port range using Open VSwitch

I am locking down a VM on xenserver to allow only port 3389 and the ports required for domain controller authentication on windows. I am trying to do this using Open VSwitch. Locking down and allowing ...
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2answers
68 views

No external network access to virtualbox CentOS6.5

I have CentOS 6.5 running locally in virtualbox. I set it up and everything was working perfectly. I came back after the weekend and I noticed the computer was frozen so I had to do a hard restart. ...
2
votes
1answer
24 views

Two LAN cables when using Remote Access Card?

I recently bought a HP MicroServer N54L and a HP Remote Access Card. Connecting to the server over a KVM viewer for BIOS setup etc. works fine, but when it comes to installing Ubuntu 14.04. the ...
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2answers
1k views

Untangle VPN setup, how to see internal addresses?

So Untangle is setup as the default gateway at 192.168.100.1/24, it is the authorative DHCP server issuing addresses from 192.168.100.100 to 192.168.100.200 and is successfully connected to the ...
2
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3answers
35 views

/etc/hosts.deny ignored in Ubuntu 14.04

I have Apache2 running on Ubuntu 14.04LTS. To begin securing network access to the machine, I want to start by blocking everything, then make specific allow statements for specific subnets to browse ...
0
votes
1answer
35 views

How to load new profile in Network manager v0.9 without nm-connection-editor using cli?

i'm working on migration of autoprovisioned Ubuntu 12.04 LTS servers from ifup (/etc/network/interfaces) to NetworkManager. /etc/network/interfaces is clean (only loopback interface is configured): # ...
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1answer
1k 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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0answers
28 views

Is it ok to attach 1 interface to 2 bridges at the same time?

Let's say I have network interfaces eth0, eth1, eth2 and eth3. eth0 and eth1 are attached to bridge br0. eth2 and eth3 are attached to bridge br1. Let's say under some special condition, I would ...
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1answer
211 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
25 views

Get dhcp ip from a specific server [closed]

In a network that comes with two dhcp servers, how can I get network configured from one server instead of the other? Let's say there are 2 dhcp servers named A and B. My computer always get network ...
1
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3answers
52 views

network usage per user in linux [duplicate]

I am administrator of an openSUSE linux server which is used by many people in our company. Today we find out that yesterday one of the users use too much of bandwidth and its important for management ...
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1answer
1k views

Diagnosing packet loss / high latency in Ubuntu

We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same ...
0
votes
1answer
52 views

“Stale NFS file handle” after reboot

On the server node, it is possible to access an exported folder. However, after reboots (both server and client), the folder is no longer accessible from the clients. On server # ls /data Folder1 ...
2
votes
1answer
61 views

e1000e Reset adapter unexpectedly / Detected Hardware Unit Hang

I have a Dell 1U Server with Intel(R) Xeon(R) CPU L5420 @ 2.50GHz, 8 cores running Ubuntu Server Kernel Version 3.13.0-32-generic on x86_64. It has dual 1000baseT networking cards. I have it set up to ...
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0answers
17 views

Is firewall blocking the ARP messages?

When a clients tries to boot via network (with PXE protocol), it fails with this message PXE-E11: ARP timeout PXE-E11: ARP timeout PXE-E38: TFTP cannot open connection dhcpd shows that it assigns ...
3
votes
3answers
741 views

Mysterious “fragmentation required” rejections from gateway VM

I've been troubleshooting a severe WAN speed issue. I fixed it, but for the benefit of others: Via WireShark, logging, and simplifying the config I narrowed it down to some strange behaviour from a ...
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0answers
16 views

Data transfer/bandwidth consumption when transferring data through different server [closed]

I have been having this question in my mind for a while now, so I am asking it here. I have my server which is hosted with a leading hosting company. In which I have a php script that does the ...
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0answers
26 views

How can I bridge a VM to a remote network?

I have a system running QEMU/KVM (via libvirt). One of its VMs needs to have a presence on a subnet that is not local to the VM host. I have a Linux system on the remote subnet. Is there a way to ...
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1answer
51 views

Ubuntu 14.04 LTE forward port to another port

I am looking for a way to forward 1 port to another internally. I have an Ubuntu 14.04 server on which I installed a game server that listens on port 25565. The game does not support multiple ports. ...
0
votes
1answer
928 views

Trixbox CentOS Default GW Problem (Multi-homed server)

I'm having an issue with a CentOS trixbox server which is dual-homed (one private facing NIC [eth1], one internet-facing NIC [eth0]). I can't seem to get the default gateway to set properly to our ...
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votes
1answer
33 views

How many data packets does it take to log in to facebook? [closed]

I am sure we send millions and billions of data packets a day but I'm curious as to how many are sent / received just over a simple interaction like logging into facebook. Even better would be if ...
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1answer
1k views

How to block internet access to certain programs on Linux

Recently, I have encountered a problem of limiting Internet Access to specific programs. Could anybody recommend a good way of doing that, without using any particular software?
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1answer
32 views

iptables destination ip and port

I am looking for a way to forward all traffic(to any port) from a pc to a certain ip. Looking at the rule below : iptables -t nat -A PREROUTING -p tcp --dport 443 --jump DNAT --to-destination ...
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0answers
14 views

Chef - handle resources changing the network interface

I'm using chef to deploy an openvpn application in bridging mode to an ubuntu node. In my recipe i'm using a bash resource to create the bridge necessary for the vpn to work. Unfortunately the bridge ...
0
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1answer
672 views

SASL - Plaintext password not accepted - Encrypted works

I have a very strange issue! SASL does not work properly, as it does not accept plain-text passwords (like Outlook sends them) Oct 2 10:35:09 srf cyrus/imap[4119]: accepted connection Oct 2 ...
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0answers
24 views

SYN-ACK with identical MACs

What could cause a CentOS machine to respond with SYN-ACK packet having both source and destination MACs set to the address of the NIC from which the packet is being sent?
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22 views

Routing, OpenVPN and blocked Packets to Router

I have a running Zentyal Router. Now I have created a Softether-VPN (which wraps OpenVPN basically), to connect to this network per Network-Bridge/L2-Switch. So, when I connect per VPN I am in the ...
0
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0answers
23 views

getting rid of unused listening ports (kernel)

As a follow-up on this question, I have that issue (ports that are reported listening in netstat, but have no process linked to it) and it's the nlockmgr that's actually using these ports according to ...
1
vote
1answer
32 views

Poor performance executing “cp -al” over a NFS export

I am in the process of implementing a backup of a WD My Book Live Duo. This device is configured with software RAID0. The backup source directory is the root of the device, and the destination is a ...
0
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0answers
26 views

Use Cisco VPN connection of another Computer using linux iptables and routing

I have the following need. I have a system that is connected to production environment using a cisco VPN client. At any point of time only one connection is possible. Right now I ssh to that PC and ...
0
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1answer
15 views

VPN Connection pooling?

I'm having a problem on PFSense https://forum.pfsense.org/index.php?topic=23914.0 where I can only connect one client with a PPTP VPN to a VPN Server outside out network. PFsense is our firewall and ...
2
votes
1answer
74 views

Linux bridging for KVM

I have a Debian Wheezy machine on which I tried to setup KVM with bridged networking. Unfortunately, the bridge does not appear to forward traffic correctly. My setup is the following: The physical ...
0
votes
1answer
49 views

SSH connection timing out on certain clients only

I have a server that has around 100 SSH tunnel connections active from client servers across Canada and the US. We use the same device that runs a custom build of Ubuntu and load that on each client ...
0
votes
2answers
37 views

Can I configure a connection a network with a gateway with a static ip to a network where the gateway address is assigned via dhcp?

I have two networks with each gateway on a separate network device on a single computer. One is a static ip network on the ethernet device, the other is a wifi connection to a router that is assigning ...
0
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0answers
65 views

All EC2 outbound traffic is blocked

This is access from WITHIN an EC2 outbound to anywhere. (EC2-BAD) I can get INTO the instance via ssh and I can run my webserver on port 80 and I can ping from another EC2 (EC2-GOOD) in the same VPC. ...
3
votes
2answers
79 views

same subnet,different VLAN in Virtual machine

I have 2 VLAN,VLAN 100 and 101 but only one subnet i am trying to make this work with virtual machine so that VM will have two IP address in same subnet but will actually be in two VLAN. steps ...
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0answers
20 views

IPSEC on linux with multiple remote ISP

I have configured 2 ipsec VPN connection from my linux server to my clients locations. the reason being the client has two ISPs a primary and a secondary on. The client wants to switch to secondary ...
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0answers
20 views

Weird tty behavior

When connecting to a group of servers in office, I sometimes get the following weird behavior: For any character I type, the previous character that was typed is displayed. So if I type "Hello" I ...
0
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2answers
1k views

How to route broadcast packets from machine with two network interfaces on same subnet

I run RHEL 5 and have two NICs on one machine connected to the same subnet: eth0 192.168.100.10 eth1 192.168.100.11 My application needs to receive and transmit UDP packets (both unicast ...
0
votes
3answers
70 views

locking up a linux box on a foreign network

I have an app that runs on a Linux server and is accessed via each user's web browser. My app contains proprietary code that I need to keep secure. I want to install the app in a client's private ...
1
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1answer
729 views

Check packet vlan tag using Tap virtual interface

I am trying to learn how to implement virtual interfaces using the Tap driver. So far my understanding is that using the tap driver I can create a virtual interface and then have a userspace program ...
2
votes
1answer
136 views

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 ...