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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What would cause named to send out hundreds of bogus responses?

My DNS server running RHEL 6.6 is actively sending unsolicited DNS responses to a couple of IP's. By unsolicited I mean that there is no incoming request from the external IP, the DNS server seems to ...
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26 views

What's the recommended way to restrict Internet access per process using SELinux?

Before I have tried to do this using a phony user and iptables to execute commands that needs to be restricted. However now the commands need to read configuration set by each user's environment vars ...
3
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160 views

Hyper-V lost synthetic NIC after Debian 8 dist-upgrade?

I'm running a Debian 8 vm on Hyper-V (Win Srv 2012R2) and when I did a dist-upgrade of stable, I lost all network connectivity. Using the console, I was able to see the network interfaces as UP but ...
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29 views

network access issue and triage

We have two hosts in same vlan with same route rules. One of them is able to connect to an outside IP while on another I get failed: Connection timed out when testing the connectivity through netcat. ...
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36 views

Debian-Server: Incoming SSH/PING/TELNET/… works - outgoing does not

I've mentioned a strange behavior of my linux-system: After rebooting the system I can connect to it via SSH and the server responses to PING. But the server itself can not ping any other servers. # ...
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77 views

Dynamically enable IPSec for IP connections between many servers

For a given list of internet server (example): S001 - 45.67.89.12 S002 - 67.78.90.34 S... S999 - 98.76.65.54 I want to talk from each server to any other server to any TCP service using the public ...
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64 views

HTTP DELETE timeout between Nginx and Application

We're facing a really weird error using HTTP DELETE, the symptom is occasionally the user gets a 504 (timeout) error in the browser. The requests flow through the steps described below: Browser -> ...
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17 views

How are kernel networking settings handled in OpenVZ containers?

I’m a little confused on how containers handle networking. For our normal systems, we’re enforcing things like Disable Source Routed Packet Acceptance, Disable Send Packet Redirects, etc. We usually ...
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62 views

How to write firewalld rule with rich language

How can I write a rule for firewalld using rich language which restricts packets from a particular port and particular protocol. For IP tables I wrote a rule like: firewall-cmd --permanent ...
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94 views

Linux - Outgoing connections from process timeout after the process restarts

banging my head against the wall with this one... I have an Ubuntu Linux server, on top of which our own process which holds 40K persistent connections to external services. When the process ...
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161 views

Routing with multiple NICs on debian

I have a machine with two NICs on different network segments, I've set up routing for the different segments. It works if I run all the routing commands manually, but I can't get it to work when ...
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112 views

What are the advantages NAPI before the IRQ Coalesce?

As known there are two approach to avoid some overheads of hardware interrupts in highload networks, when there are too many hardware interrupts, that switching to them takes too much time. It is very ...
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62 views

IPsec - strange behavior

I have set up site-to-site ipsec connection between linux(debian) and mikrotik router. The tunnel is up linux configuration: config setup interfaces=%defaultroute keep_alive=60 ...
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408 views

php-fpm process in D state ,cause nfs wait rpc_wait_bit_killable

my wordpress site which is in clustered environment using NFS,nginx,php-fpm,mysql the infrastructure is hosted on amazon ec2.Under high load/traffic the php5-fpm process goes in D ...
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70 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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570 views

access tap interface in network namespace across machines

I want to be able to access services running on a TAP interface within a namespace from outside the machine where it is running. I have setup that looks like this - VM1/Machine1 +eth0 : Public ...
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166 views

How can I set ntop not to shorten host names?

With most screens in ntop, there is a list of hosts. Unfortunately, in almost every one, the host name is shorted, for some reason. When the host names follow the company standard, this results in the ...
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552 views

VMware - Broadcom 1000Gbps NIC does not link at 100Mbps to a Cisco switch port

Today we've stumbled on a very awkward situation with our VMWare Server. The server is with ESX 3.5 that has a 1Gbps NIC. We bought a brand new managed Cisco Linksys switch with 10/100Mbps interface ...
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976 views

StrongSwan - Windows 7 0 IPSec IKEv2 connection problems

I am trying to configure a roadwarrior scenario between a linux box with StrongSwan and a Windows Box with Agile VPN. I successfully configured my StrongSwan and my Windows box to connect. The Windows ...
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16 views

iptables/nat/prerouting ignores UDP packets?

The same effect on many servers with various kernel versions. There are multiple Iptables DNAT rules: iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 12345 -j DNAT --to-destination ...
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10 views

Can Spark be configured to listen on multiple network interfaces/ip addresses?

The nodes in my Spark cluster have two network interfaces each, one public and one private. Using the SPARK_MASTER_IP environment variable, I can configure Spark to listen on port 7077 on one or the ...
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17 views

Debug slow lan (ssh, nfs) file transfer

I've got two linux boxes attached to a gigabit switch. They both have gigabit NICs, cables are cat7. Testing the network with iperf shows a fast connection but transferring files with rsync, scp, or ...
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70 views

tcpdump on bridge interface (virbr) does not receive any packets destined for one of its addresses

Here's the configuration for the interface: # ifconfig virbr0 virbr0: flags=4355 mtu 1500 inet 192.168.11.1 netmask 255.255.255.255 broadcast 255.255.255.255 ether ...
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30 views

Error while trying to bring up network in SLES12.1

I am trying to bring up the eth0 adapter in SLES12 sp1 using ifup eth0 but every time I am getting an error saying: wicked: Reading config file /etc/wicked/client.xml wicked: Reading config file ...
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19 views

restart client after download .img file from PXE

I want to install pfsense using pxe. In Windows 7, I have installed the Tftpd32 software and set it up (conf file is below). The client machine downloads the image file (pfsense.img) successfully ...
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53 views

SSH (interactive) hangs during full upload bandwidth use

I work daily on SSH from a Linux desktop to an AWS EC2 Amazon Linux server and the connection has performed very reliably for two years, but in the last few days I have seen the SSH command line hang ...
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34 views

how to combine ips to increase server bandwidth?

I have several ips. Each of them is limited to 2MB/s by the network provider. How can I assign multiple ips to one server to increase my server's outgoing bandwidth? My server runs CentOS 7. Thanks!
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52 views

Maximum transfer rate iSCSI bonding vs multipath

I want to get the maximum tranfer rate with iSCSI from my virtual machine (Linux) to my Linux Storage Host. I don't know iSCSi well so I'm not sure which way is the best for performance. A: Just ...
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89 views

Using KVM with macvtap and VLANs for VM

I want to use the optimizations given for the ASAv (Page 18) which should run with KVM. I am using Ubuntu 14.04 LTS and I should configure macvtap for an higher performance. It just says the ...
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14 views

Weird behavior with multiple pool inside shared networks on isc-dhcp-server

I have a weird behavior on my dhcp-server, I am using a load balance configuration and using multiple pool inside that shared-network, I have this configuration: shared-network "my-shared-network" { ...
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63 views

nmcli static routes are ignored

I'm in doubt about how NetworkManager through nmcli manages static routes. I have a CentOS 7.1.1503 server with three network interfaces: [root@brick ~ ]# nmcli con show NOMBRE UUID ...
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18 views

Network Traffic fluctuating, even with loopback

I am using iperf tool to benchmark my network interfaces on two identical machines (Dell Blade Server M620). Both have given different results. On 1st machine, I ran server and clients as: Server ...
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140 views

Samba connection fails from OS X

The server is running Ubuntu 12.04 and Samba 3.6.3. Windows users can mount their shares without problems, using the path \\my_server.com\username and account \username. However, when I try to ...
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17 views

Output traffic on different interfaces based on origin subnet

This a diagram of my current network, http://s1.postimg.org/5689b415b/actual_diagram.png Objective Route 172.16.0.x/18 subnet web traffic to ADSL connection What do you think of this approach, will ...
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126 views

UDP packets seen on interface level but not delivered to application on RedHat

I have a problem with receiving UDP traffic on a RHEL6 server. When capturing the traffic with tcpdump, the packets are visible (checksums are correct, the destination IP and MAC match the machine's ...
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36 views

OpenVPN: routing to two VPNs

Using Ubuntu 14.04 (up to date). I'd like to use two VPNs (openvpn) a the same time. LAN is: 10.1.1.0/24 The 1st VPN, homemade, is only routing the 192.168.1.0/24 network via the tunnel. Routes ...
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39 views

Local Network not working on one server while the other one works fine

So I have two servers (davros - working, kraken - not working) on the same subnet (10.10.28.0/24). They both have the same configurations and yet only one of them works. (Also, I should note that ...
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51 views

Changing source MAC address of routed packets

I have linux box with one network interface and IP forwarding enabled. Let's say my IP address is 192.168.1.1 and MAC is 11:11:11:11:11:11. When a packet which is not targeted for my host arrives, it ...
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41 views

iptables rule limiting the number of connection in a broken pipe case

I am limiting the number of SSH connections using iptables but in case of, for example, a broken pipe (computer goes sleep mode, network problem, etc.) I am no longer able to reconnect. The rule I ...
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0answers
35 views

vnstat output giving different results

I ran vnstat -d and vnstat -m and compared the results to vnstat --dump. The values between daily and monthly are off by several bytes. Is this expected? I would imagine last months data and ...
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350 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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42 views

how to divert incoming all tcp packets at eth0 to socks proxy and to eth1 of same host?

I have a three ubuntu linux hosts. host 1,host 2 and host 3. I want to pass data from host 1 to host 3 via host 2. But specifically I want to pass all incoming traffic of host 2 to socks proxy then to ...
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61 views

Spurious retransmission, Dup ACK and HTTP 408

I have a server which serves as sms gateway (using kannel) and have multiple client connecting to it, but recently this one client with their particular IP said that they can't send to my server and ...
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43 views

Get Original Destination Port From iptables

I would like to create a local server that acts as a proxy for all trafic, but how would I determan the original ports when using iptables to rederect the network traffic. I need this for when the ...
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111 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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33 views

Routing private IPv4 addresses internally

I have the following set-up involving two KVM hosts and numerous virtual machine guests on each. The guests communicate to each other on both hosts via [192.168.216.0/24]. [192.168.216.42] is ...
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42 views

IP hashing filter in traffic shaping

I am using a traffic shaping by IP hashing filter. I have Five networks /24 : 192.168.1.0/24, 192.168.2.0/24 .. 192.168.5.0/24 so i create a table with 5 cells and each cells has 256 cells. this is ...
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163 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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57 views

Process-wide VPN connection via openconnect

I'm using openconnect to connect to a remote endpoint and SSH onto the machine inside the remote network. The problem is, when I do create the connection, the machine I do it on is unresponsive for ...
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114 views

dhcp relay with failover to local service

I'd like to set up a dhcp server which normally relays to a central site, but has a pool of addresses to hand out if the link to the central site goes down. I'm using isc dhcp server on Debian, but ...