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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Why are my multicast packet discarded?

I have two boxes and I have some issues when tcpreplaying a pcap full of multicast from one machine to the other. I see the packet incoming on the destination machine thanks to a tcpdump instance. ...
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21 views

Can I route traffic destined for a local interface out another interface?

I'm trying to set up a testbench for a transparent device (called TD from now on). The goal is to make sure it forwards and logs correctly. I need to use just 1 machine + the TD in the test bench. ...
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1answer
22 views

iptables: does a scanner knows if you DROP packets?

I know how REJECT and DROP chain works. But, as I read here REJECT vs DROP when using iptables, user Dagelf said that the server still replies with TCP SYN/ACK. Does the scanner knows that a packet ...
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12 views

PIV authentication on redhat

I'm looking for a solution, or set of technologies, (etc) - for setting up a mixed (win 7, rhel 6.5) network with centralized login using smart cards (PIV). I know that this is possible using a ...
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21 views

Massively large number of packets dropped by interface

I have a virtual machine on ESXi 5 acting as a firewall for a PBX, it is running vyatta. When I run tcpdump on any interface, I get some ridiculous numbers! e.g. 4 packets captured 402 packets ...
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10 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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2answers
28 views

what does `pipe <number>` mean in `ping` output?

While running a test to diagnose some alleged network problem, I got this output from ping: --- r01c01b11n02 ping statistics --- 30000 packets transmitted, 29995 received, 0% packet loss, time 6309ms ...
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1answer
27 views

Software for emulating networks and NAT

I am working on a software that I need to test with different types of NAT, and I would like to set up a test environment I can reconfigure in different NAT modes. I would like to have: ...
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1answer
45 views

Assign different Hostname to different NIC

I have four network card on my server, I have assigned each with an specific IP now I want to set an different hostname for all the interface? What is the difference between setting the hostname in ...
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1answer
31 views

Is it possible to configure Apache to not listen on port 80 when connecting from localhost

Is it possible to configure Apache to not listen on port 80 when connecting from localhost, but allow the connection on port 80 from an external IP?
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1answer
31 views

Netstat hangs: why?

Sometimes (not too often at all) when I type "netstat", it takes over 5 seconds to return. While other times is instantaneous. I have been observing this for weeks on my server (CentOS 6.4), but I ...
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1answer
35 views

Host doesn't send ACK-SYN packets for transparent proxy

I am setting up a transparent proxy using haproxy, the setup works without the 'source 0.0.0.0 usesrc client' line. When I add that line in, the endpoint is called from the original client's ip ...
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1answer
41 views

Can't connect to 2 different Linux computers via VNC (local network)

I have a problem connecting to Vino VNC server with 2 Linux Computers running Xubuntu. The computers are Based on the ODroid U3 chip which is ARM based. When both of the ODroids are on the same ...
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3answers
59 views

How to find out capacity for network interfaces?

I could get the capacity for the network interface by lshw, but which file in sysfs is this information stored(i.e. which file in /sys/class/net/eth0/device/ directory)? $ sudo lshw -class network ...
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3answers
38 views

Is it possible to route network traffic according to user ID?

On my Debian system, I'd like one of my users to use a different network interface as their default route for all internet traffic. I know how to use iptables to block the other interfaces, but not ...
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1answer
33 views

disable a network interface on booting ubuntu

I use ubuntu 12.04. I need to boot with one of the network interfaces 'eth1' down. I tried adding sudo ifconfig eth1 down to /etc/rc.local However it seems the interface is brought up and ...
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1answer
35 views

Linux 25 port routing (tunneling/forwarding)

I have: 1) Centos server 1 with postfic/dovecot mail servers IP1 45.45.45.45 (DNS: host1.com.ua) server 1 cannot make outgoing request to 25 port because Internet Service Provider block it! ...
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1answer
41 views

How do I close ports in Linux for security reasons (KVM)? [closed]

I am going to set up a KVM virtualization server on CentOS. The host machine and several of the VMs will have a dedicated IP addresses. I'm going to need to close off unused ports and probably ...
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45 views

eth0 NIC Link is Down repeating message in kernel log

I've noticed since few days ago that same repeating kind of messages occurs and I positively can say that nothing was intentionally changed (installed/uninstalled) in that period. here's sample of ...
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15 views

Couldn't load target `DNAT':No such file or directory

Trying to do some ipv6 nat and running into an error from ip6tables $ip6tables -t nat -N IPV6-BRIDGE $ip6tables -t nat -A PREROUTING -p all -d 2600:3c01::f03c:91ff:fe6e:2563 -j IPV6-BRIDGE $ip6tables ...
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0answers
30 views

Pinging to google.com from a particular interface

I am connected to the internet via wlan0(wifi) and also have an ethernet port(not connected to the internet). I am looking for some iptables rule / route addition, which will let me do a ping via eth1 ...
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3answers
381 views

Which private IP addresses can I use? [closed]

I have a dedicated server where I'm running several web-facing virtual machines on public IP addresses; I pay my hosting provider for each IP. I would also like to run virtual machines with private ...
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1answer
189 views

Should /etc/hosts contain an entry like '127.0.0.1 localhost myhost.example.org myhost'?

When looking at a variety of Linux and FreeBSD systems, I've noticed that on some systems /etc/hosts contains an entry for the public hostname of the host, but not on other systemst. What is the best ...
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38 views

Multicast route setup for multiple interface

Currently I have the below eth5 to receive multicast data for 239.1.1.31. It works. $ ifconfig eth5 Link encap:Ethernet HWaddr E4:11:5B:94:E1:F3 inet addr:10.185.2.2 ...
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2answers
68 views

How do I throttle network activity in Linux?

How do I throttle network activity, system-wide? Say, I'm running rsync on a large archive with a cron, or a torrent server, or both. It's important that these activities will be running, but they ...
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1answer
40 views

Running a custom script when StrongSwan connection is established

I have StrongSwan VPN server set up on a Debian host, and would like to run a custom script when a client connects to it. The only thing I have come up with is periodically checking the contents of ...
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61 views

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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1answer
27 views

Linux 802.3AD port bond only shows one port

I have an Ubuntu server (13.10) machine with multiple NICs I'd like to bond together. Here is the network configuration on the server: auto eth2 iface eth2 inet manual bond-master bond0 auto eth3 ...
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1answer
40 views

What's the difference between eth0:1 and 2nd eth0?

In Ubuntu server, I configured eth0:1 like this in /etc/network/interfaces file # The primary network interface auto eth0 iface eth0 inet static address 192.168.1.111 netmask ...
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24 views

Do I need a firewall if the service doesn't listen on all interfaces? [duplicate]

Short version: I have a CentOS 6.5 with two NICs, one connected to the internet and one connected to the internal network. The services that shouldn't be accessible to the internet don't listen on ...
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3answers
58 views

benefits of iptables on VPS? [duplicate]

Say I have a well updated Linux VPS serving HTTP content on port 80 using apache. What would I gain by enabling IPtables? I can see no obscurity gains since the machine has a port open. Also, since ...
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2answers
18 views

Http Persistent Connection (keep-alive) and port numbers

Is a persistent http connection (keep-alive), always bound to a specific port, or can it use a range of ports?
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2answers
27 views

APF and iptables on router - disallow SSH on specific subnet host

I have a CentOS terminal working as a router with APF installed. Also 1 terminal with 3 NICs (3 IPs) is using that router as a Gateway to access the internet. What I want is APF to block SSH access, ...
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1answer
35 views

Mininet additional veth pair between host and server

For those who don’t know - Mininet is a tool that allows for the automated creation of multiple OVS switches, chroot linux ‘containers’ as hosts and links them all together to prototype OVS powered ...
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1answer
52 views

Linux IPSec between Amazon EC2 instances on same subnet

I have a requirement to secure all communications between our Linux instances on Amazon EC2 - we need to treat the EC2 network as compromised and therefore want to protect the data that's being ...
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0answers
30 views

iptables - hashlimits, why it calculate all to seconds

I've tried to set 'synflood' limits with hashlimits, those are my snippet of rules: iptables -A SYNFLOOD_CHECK -p tcp --syn -m hashlimit --hashlimit-above 10/s --hashlimit-burst 6 \ ...
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1answer
27 views

Unable to add a static route: SIOADDRT: Network is unreachable

I've been bashing my head against a wall for a few days trying to figure this out: My ifconfig is: eth0 Link encap:Ethernet HWaddr 00:50:56:BB:XX:XX inet addr:192.168.36.132 ...
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25 views

Will iBGP fix this routing scenario?

I have to firewalls running for a cloud service in a data centre providing HA internet for currently around 40 machines. Each machine is a Linux based router and has it's own 10Gbit feed from ...
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1answer
54 views

IPTables: Firewall with just one Eth device? [closed]

Admittedly I am a novice in the area of firewalls. But I have read on the IPtables and Firewall theory and command options. There is a general diagram by Rusty Russell, the creator of IPtables: ...
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2answers
63 views

ARP responds with single MAC address on Linux server with multiple interfaces on the same network

Linux server has 2 active network interfaces: IF:eth1 IP:192.168.1.1/24 MAC:11:11:11:11:11:11 (1GbE) IF:eth2 IP:192.168.1.2/24 MAC:22:22:22:22:22:22 (10GbE) The idea is that the ...
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1answer
20 views

Forward a host network traffic to another host with the exception of the ssh service

I am trying to redirect all the network traffic received in a old host to a different new host. For that i created two new rules on iptables of the old host: echo 1 > /proc/sys/net/ipv4/ip_forward ...
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43 views

Proxmox internal network configuration

We have several servers (with one nic) staying in one rack in hetzner. Proxmox is installed on each one, and they are combined in proxmox cluster. The goal is to create network, between virtual ...
2
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1answer
166 views

How to ping ipv6 interface

I'm trying to get familiar with ipv6 I don't understand why I can't ping this interface at the inet6 addr eth1 Link encap:Ethernet HWaddr 08:00:27:77:9e:77 inet addr:192.168.33.10 ...
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0answers
55 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 ...
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24 views

CentOS 6.5 with Oracle XE in virtualenv

I'm running a CentOS 6.5 with installed Oracle-XE. I created a virtualenv where I run my Django-NGINX-Gunicorn Webserver. Locally I can access XE via SQL Developer but when I try to access the ...
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1answer
54 views

How can I configure iptables to forward and forget?

I'm trying to create a front controller where users can connect to a specific port and have their connection redirected to a different IP/port. The reason I'd like to be able to do this is for ...
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17 views

Qemu/KVM: packet queueing from/to guest

I am new to virtualization and trying to understand the pakcet path from guest to physical nic and vice-versa. I am partiaularly interested in understanding what are the various queuing points from ...
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2answers
80 views

Routing Internet traffic through computer on another subnet

Ubuntu box server has 2 network interfaces: eth0 50.57.71.100 eth1 10.182.161.100 Ubuntu box client has 1 network interface: eth0 10.177.30.100 server and client can already talk to each other ...
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15 views

Improbably high bitrate in the output of “iw wlan0 link”

I am trying to determine the bitrate of a wireless connection that uses the nl80211 driver on a Linux 2.6.39 machine. I am actually using a Netlink socket internally, but the effect is the same as ...
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1answer
28 views

Tunnel interface inside Virtualbox IP forwarding

I am working on a solution to expose a development stack that resides inside a Virtualbox guest up to the Internet through OpenVPN tunnels. OpenVPN client fires up inside the guest VM and connects ...