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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Create Bridge interface on linux board

My current configuration and topology look like below: +++++++++++++++++++++++++++++++++ +++++++++++++++ | Linux Board eth0 | | Switch | | with openWRT ...
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Ubuntu server drags network speed down to 10Mbps [migrated]

I'm running an Ubuntu Server (14.04) on my home network. It acts as a OpenVPN server (Bridged, not routed) and it runs one Virtual Machine (KVM, through a bridged virtual network device (br0)). The VM ...
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IPV6 address is not working [on hold]

I am newer to red-hat 7 and now I am trying to ping two systems using ipv4 and ipv6 addresses,but pinging with ip6 is not working,showing an error message "destination unreachable".Please any one ...
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1answer
42 views

“net.c:577: sendmsg() failed: Operation not permitted” in dig Output

I am running Bind 9.10.2 version on CentOS 6.6 machine. While running the dig command, i am getting "net.c:577: sendmsg() failed: Operation not permitted" notification. dig utility is giving me an ...
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2answers
60 views

Can iptables automatically drop established session after certain seconds?

Can iptables drop automatically an established output session after certain seconds e.g. 30 sec. since its launch? But I want to restrict it only for destination port 80 and 443. The purpose is to ...
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1answer
23 views

Method to hijack or otherwise exploit ssh [on hold]

I plan on using plink to connect external Windows computers to application on network I'm administering, by employing port forwarding through ubuntu server. Since recently there have been various ...
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2answers
36 views

Clear TCP sessions

I am trying to use iptables to reject packets as well as reset the TCP connection. My rule is: iptables -I FORWARD -p tcp -s 10.0.0.10 -j REJECT --reject-with tcp-reset If 10.0.0.10 is SSH'ing into ...
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16 views

Linux router showing packet loss

I have two linux boxes that are using a third box as a router. Packets flow normally. BoxA(10.0.0.10) -> (10.0.0.20) RouterBox (172.16.50.20) -> BoxB(172.16.50.30) When I run mtr from BoxA to BoxB the ...
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1answer
28 views

forwarding ping using ip route [on hold]

I have a Linux setup which consists of two interface. A local LAN interface and virtual interface. ETH0: 150.10.15.194 PAN0: 192.168.255.209 I would like to set rules that route all ICMP echo ...
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2answers
38 views

SSH Connection through a Reverse (Remote) SSH Tunnel

This is the setup I have : a Linux box A inside a LAN behind a firewall. a Linux server with a fixed IP address that is accessible from the internet. I want to be able to connect to the Linux box ...
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41 views

reducing bufferbloat in linux web server

I'm looking for all the buffers I can tune in linux as well as their order of operation. On the server, nearly all operations are run over the TCP protocol. I want to eliminate bufferbloat to improve ...
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2answers
115 views

Stop China from connecting to my Google Compute Engine server

My company has a Google Compute Engine server hosted in North America. We get so many Chinese IP addresses sending requests to port 11 that it is costing us money for the ingress. Our firewall blocks ...
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1answer
2k 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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7 views

bird4 - OSPF not learning/distributing /32 routes in hub-and-spoke topology

in my hub-and-spoke setup all the boxes are happily exchanging local LANs routes through bird4/OSPF. The links between the hub and the spokes are VPN p2p links and I need the address of every spoke's ...
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12 views

Changing value of tcp_fin_timeout in unix machine

I was looking at this article in which they have mentioned how to increase two property for better performance of application if we see lot of TIMED_WAIT connections My question is: if I modify ...
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6answers
13k views

Can't start CentOS 7 “network” service

I Can't start CentOS 7 "network" service after disabling and removing "NetworkManager" service. When I check the network service status, it comes up with the following error: #systemctl status ...
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1answer
116 views

Is it possible to process millions of datagrams per second with Windows, using a vendor agnostic API? [on hold]

I am investigating if I can implement an HPC app in Windows that receives small UDP multicast datagrams (mostly 100-400 Bytes) at a high rate, using a dozen or up to maybe 200 multicast groups (i.e. ...
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1answer
1k views

IP setting in CentoOS 6.2x64 by XenCenter 6.2

I have setup a Guest CentOS virtual machine in Xenserver.. I have updated the Xentools but i cannot find the option to config my IP Address which is showing to be 'unknown' currently. All i need to do ...
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1answer
22 views

Routing issue on Linux with Mobile Broadband

Note: This is a "cross-post", I asked this same question on "superuser" StackExchange site, but without obtain any answers, just a comment (now curiously disappeared). I've thought this site is ...
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35 views

SynProxy can not return syn ack packets with asymmetric dual bridge topology

I have a asymmetric dual bridge topology as shown below when i connect from 172.16.11.5 and 172.16.10.6 with ssh but i can not connect because of SynProxy. ------- ...
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1answer
13 views

How do i keep ISC-DHCPD from offering different IPs when there is two requests from the same MAC

I have a set of Nodes which get their addresses from ISC-DHCPD. Since they boot using PXE, there will be two rounds of DHCP (one from the PXE, one from the OS) and for some reason, ISC-DHCPD will ...
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15 views

Iptables drop forwarded traffic destined for interface IP address

I have a small VPN setup where I use IP tables to nat traffic coming in the vpn0 interface to the IP address of the eth0 interface. These rules look like this: iptables -t nat -A POSTROUTING -o eth0 ...
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1answer
1k 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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17 views

Need all local traffic through Debian - Routing? [migrated]

Been dealing with this for some hours now and my head are really spinning. So I got this cable network router (192.168.0.1) that Im trying to pass all my local traffic to. But I cannot for the life ...
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34 views

Linux traffic control input interface using more than output interface

this thing is driving me crazy for days now simple nat router using `iptables masquerade and simple linux tc using htb here are the commands iptables -t nat -A POSTROUTING -o eth0 -s 10.1.1.2 -j ...
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46 views

Mounting encrypted Samba share (linux server/client)

I'm trying to set up encrypted samba access. In order to achieve that I've added 2 lines to [global] scope in smb.conf: server signing = mandatory smb encrypt = mandatory But unfortunately I can't ...
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1answer
64 views

Starting to learn about IPtables, why do I need this rule?

I have been reading all day about IP tables, how the rules work, sets of rules for basic webservers, etc. Now I`m trying to configure my webserver with IPtables using this thread as a starting point: ...
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1answer
50 views

docker0 bridge status toggles between enabled/disabled, what could be causing that?

I have some CoreOS bare metal instances that are displaying unusual behaviour on the docker0 bridge device. On one of the instances where this has been occurring, I'm running couchbase server and it ...
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1answer
986 views

Network aliases on boot on Fedora 17

We have a fedora server(Fedora release 17 (Beefy Miracle)) with a few aliases on the main NIC that don't get setup during boot. Here's my config: # cat /etc/sysconfig/network-scripts/ifcfg-em1* ...
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2answers
27 views

Creating Virtual Proxy Server

I know this is not this kind of forum, but I can't find anything in google that really answers my question. Is there possible to create a Proxy server running in a Virtual Machine using only 1 ...
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1answer
45 views

dual-homed Centos 7 cannot be ping'd or ssh'd from some on LAN, sees ssh connection refused on one subnet

I have 2 subnets, A and B and a router connected to both A and B and the WAN. I have 4 servers dual homed on subnets A and B, 2 of them are Mac OS and 2 of them are Centos 7 (1503). They are all ...
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1answer
24 views

port forward in INPUT level

I want to change the destination port of the ipv6 packet in the INPUT level. So I tried to use ip6tables with nat in the INPUT level but seems this command does not work # ip6tables -t nat -I INPUT ...
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1answer
1k views

How to stop a infinite running process(ztail) started by a ssh session after that session is closed

I have a peculiar problem. My server supports multiple ssh session simultaneously, so that multiple admins can manage it simultaneously. We have a command which calls ztail to show the compressed log ...
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home network bridge + access point [migrated]

I want to create a wired bridge to a wifi setup a firewall + intrusion detection and then setup a wifi-access point for lan-out I currently have a d-link 1200 extender setup as bridge, my desktop ...
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1answer
614 views

Limiting bandwidth with hashlimit (e.g. kb/s — not connections!) doesn't work, though the man page says it should

According to the iptables-extensions man page hashlimit can do bandwidth limiting: "flows exceeding 512kbyte/s" => --hashlimit-mode srcip,dstip,srcport,dstport --hashlimit-above 512kb/s ...
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52 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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2answers
965 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 ...
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1answer
15 views

Upgrading Web Application's Systems' Kernels for IW10 & other related improvements - upgrade all machines? LB first? Most important?

Stackers - We're making the push to upgrade the systems for our web app to take advantage of the various TCP improvements becoming more readily available (e.g. ...
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1answer
31 views

AutoFS mount multiple CIFS Shares to same directory

As long as I had only one mount everything was fine. file: /etc/auto.master /mnt /etc/auto.srv1_share1 file: /etc/auto.srv1_share1 sh1 -fstype=cifs,rw,user=jdoe,domain=srv1,noexec,password=xxx ...
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1answer
197 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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29 views

What's the best way to create a captive portal access point if my authentication is on a website?

I have my access point set up with dnsmasq and hostapd. Hostapd supports authentication but it is local authentication. I need the user to be limited to a specific login URL, where once they hit the ...
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2answers
166 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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2answers
63 views

Port 22 is accepting connections, but not visible in netstat, unhide etc

So I have this weird issue where one of my boxes is accepting connection on the ssh port (22) even after sshd is stopped. I tried to identify the listening process by the typical means sudo netstat ...
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48 views

IP-rules don't seem to be working on CentOS-6.6

I faced a bit odd difficulty with policy-based routing on CentOS-6.6 server. I have a setup where I need to enroute all packets originated from 172.25.0.0/16 destinated to 172.24.0.0/16 and some ...
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3answers
3k views

How can I achieve OpenVPN client routing without NAT on Linode

I've set up an OpenVPN network, and it is working properly in the sense that I can access the inner/LAN machines from the remote client. However, my problem is that all traffic from the remote ...
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1answer
1k views

Infiniband port status UP but can't open UMAD port ((null):0)

My system has 2 infiniband devices, one of which has both the ports up. $> ibstatus Infiniband device 'mlx4_0' port 1 status: default gid: fe80:0000:0000:0000:0002:c903:000f:0a9f ...
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3answers
168 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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1answer
1k views

Kali SYN Flood (Metasploit), not denying service

I have a server with apache2 installed. I tried to do a dos attack on the server by using kali linux syn flood attack, but i am still able to access the website on the server. msf auxiliary(synflood) ...
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1answer
26 views

Running OpenVPN on Xen node causes guest VM to view all inbound connections as originating from the node IP

I have two node servers running Xen 4.2 -- I'll call them Node A and Node B. Node A is running OpenVPN as the server. Node B is running OpenVPN as the client. Both nodes host a number of Xen guest ...
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202 views

Update version of network manager

In shell on sever I see following error after launching several commands: Error: nmcli (1.0.0) and NetworkManager (0.9.9.1) versions don't match. Force execution using --nocheck, but the results are ...