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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One second delay before tcpdump returns packets

Using Ubuntu, I'm trying to sync tcpdump sniffing with self-identifying "pings" from a client device. The problem is that getting precise starts and stops is made difficult by what looks like a ...
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2answers
343 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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3answers
156 views

how to configure two ip blocks for use on a network

My ISP has given me a /30 and a /27 ip block I can use. for the sake of not giving out my ips I'll use 192.168.1.192/30 and 192.169.1.224/27. I'm not using a router in my setup, I only have a switch. ...
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2answers
1k views

Server Won't Autonegotiate to 1Gb Interface

I'm having an issue where some of my servers are not autonegotiating to the 1GB/s speed from their 1Gb NIC interfaces. These servers are Dell R610s running RHEL 5 wired to a Cisco switch. I have ...
2
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2answers
969 views

IPv6 configuration SIOCSIFADDR file exist

I am configuring IPv6 address in a Debian machine, and this is what I have in my interface file. auto eth0 iface eth0 inet6 static pre-up modprobe ipv6 address 2001:23:207:141:0:0:0:0 ...
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2answers
234 views

Linux NetBIOS name relay

I have a bridge, over WiFi, that is using parprouted to fudge ARP so that routing works. Is there anything like dhcrelay (which relays DHCP requests) but for NetBIOS (Windows File and Print Sharing) ...
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1answer
2k views

strongSwan ipsec setup, couple of questions

i am trying to setup a IPsec bridge between my home network and my office network. I want to use StrongSwan to encrypt the traffic as IPsec i am trying to follow this guide A brief description of ...
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1answer
1k views

Iptables - Forwarding + Masquerading

I am new to iptables and trying to set my linux server as a gateway for my other computers.So naturally I am playing with iptables and needed some help My server has 2 NIC cards, eth0(WAN) and ...
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4answers
3k views

Hostname problems in CentOS 5.5

I just set up a CentOS 5.5 machine on my local network and attempted to modify the hostname by editing /etc/sysconfig/network file. When I'm logged in locally the change to the hostname is reflected ...
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2answers
54 views

IPv6 Stateless Autoconfiguration route advertisements

In our network, we have a Cisco router acting as the core router, connecting all our sites to the main site. We also have a Linux firewall connecting us to the Internet. Site 1 --\ ...
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1answer
1k 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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1answer
439 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 ...
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1answer
975 views

OpenVSwitch between namespaces

I'm trying to configure a bridge between two TAP interfaces each created inside their own network namespace, on Linux. I'm using OpenVSwitch as software bridge. These are the steps that I believe ...
2
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1answer
141 views

Linux router: bandwidth of client

I am trying to build a linux router (captive portal) with a local RADIUS server for authentication. I want to log the bandwidth being used by each client on my network. I want to associate bandwidth ...
2
votes
1answer
110 views

How can I create an environment to test OpenVPN with in a test lab?

I have a test lab that I would like to use to test a site-to-site VPN setup with using OpenVPN. What is the minimum amount of hardware that I need and how should it be configured so that I can mimic a ...
2
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2answers
9k views

iptables: How to forward packets with destination port 80 from eth0 to eth1?

I've http and https traffic coming from several machines to my eth0 on my Linux machine, but I want to forward these traffic to eth1 which has the access to the internet. And do the complimentary ...
2
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1answer
473 views

Limiting a process' network access on Linux?

I've been researching how to sandbox processes, and I came across cgroups, which looked promising. I'm not super interested in using virtualization or strace for this, since I want programs to run as ...
2
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2answers
454 views

Linux does not get IPv6 default gateway from Cisco ASA5510 on autoconf

My ASA 5510 has the following configuration for an interface. My Ubuntu box (2.6.35) connected to this network will correctly autoconf an IPv6 address, but it will not set a default route. interface ...
2
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1answer
291 views

Simple Internal DNS Set-up

I have a few domains pointing to my router which then forwards them onto a server within my firewall. The server is running apache2 and everything works well - my website pops up. I have set up a few ...
2
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1answer
1k views

Iptables - forward email ports?

im trying to open some local ports (LAN) and then re-direct them to another server (WAN) using iptables. Here is my config: #WAN allow-hotplug eth1 auto eth1 iface eth1 inet static #Tarjeta red WAN ...
2
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1answer
598 views

Linux: ip alias versus iproute

When setting up a web server with multiliple IP-based virtual hosts, I've always used the eth0:x alias notation in /etc/network/interfaces. The wiki on my hosting provider states however that this ...
2
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1answer
321 views

Redirecting traffic based on ports (iptables)

I am currently working on an application that is able to conduct ARP poisoning so as to become the man in the middle and do some intelligent filtering. I will explain the problem in details in steps ...
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3answers
436 views

Performance penalty of multiple IP's per network interface

How can I measure the performance penalty of a network adapter that is configured with 2 IP addresses per eth0 ? The network card has 2 physical interfaces (ports): eth0 and eth1 with only eth0 ...
2
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1answer
997 views

Distribute IP packets accross different NIC queues with MSI (Message Signalled Interrupts)

NetXtreme II BCM5709 Gigabit Ethernet NIC supports MSI feature (Message Signaled Interrupts) and it has 8 queues. Each queue has its own Interrupt handler in /proc/interrupts. What I am trying to ...
2
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1answer
204 views

Consumer board for 4* commodity cluster in tetrahedral back-to-back GB-lan topology

I'm not very sure what consumer board to choose for such a configuration. Im planning to build one or more "Beowulf-like cluster" (starting with one for testing), one such cluster consists of four ...
2
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2answers
156 views

RSync stalls after 32768 bytes

I have an issue which I am struggling to understand. I have a server which is hosted by a business parter on their network but my team is responsible for installing and configuring software to this ...
2
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4answers
466 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 ...
2
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1answer
161 views

Rate limiting udp packets destined to a linux machine

Is there any way to ratelimit udp packets destined to my linux machine? I am sensing some udp packet drops destined to my machine. Was there any default udp rate limiting conf in linux? I have seen ...
2
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1answer
57 views

Linux: Is it possible to assign an IP that is on another server and network? [closed]

I have two linux servers in two different datacenters with the following IPs: Server1: 4.4.4.4 Server2: 8.8.8.8 and 8.8.8.9 I need to route all traffic from 8.8.8.9 (Server2) to 4.4.4.4 (Server1) ...
2
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1answer
108 views

SSH: Tunnel multiple ports to remote server

See attached diagram. Host A - Windows server Host B - Linux server Host C - VMWare ESXi server From host A I can SSH to host B over the VPN tunnel. I can ping host C from host B, but not from ...
2
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1answer
685 views

Unable to set proxy to “subscription-manager repos --list” -command

I have RHEL6 system that is registered to rhn via subscription-manager. I'am trying to install package java-1.6.0-sun-devel which is in rhel-6-server-optional-rpms repository, According to this Redhat ...
2
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1answer
602 views

CentOS, ifdown on virtual interface removes IPv6 addresses on physical interface

In CentOS 6.4, when using 'ifdown' on a virtual interface, the IPv6 addresses configured on the physical interface are also removed. I expect only the virtual interface to be changed. How can I ...
2
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3answers
997 views

Bridging eth0 to wlan0

I'm trying to create the followig setup: +----------+ | Wi-Fi | +----------+ ...
2
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1answer
548 views

FreeBSD 2 network cards

We have server with 2 network cards with FreeBSD on it. 1 card used for internet (works fine) and another one for local network connection (to 192.168.227.0/24 net). When i try to ping gateway of ...
2
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1answer
150 views

Configuring eth0 and eth1 on PowerEdge 2900 assigns both to same adapter

I have the following in my /etc/network/interfaces file auto lo iface lo inet loopback auto eth0 iface eth0 inet static address xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx gateway xxx.xxx.xxx.xxx auto ...
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2answers
2k views

Keep source IP after NAT [closed]

Until today I used a cheapy router so I can share my internet connection and keep a webserver online too, while using NAT. Users IP ($_SERVER['REMOTE_ADDR']) was fine, I was seeing class A IPs of ...
2
votes
1answer
1k views

Network Packet Out-of-Order/Duplicate ACKs

I'm currently having a very large problem with network performance from a new DataCenter that we just moved into, and honestly I'm at a loss where to proceed; so I'm looking for some inspiration. The ...
2
votes
1answer
709 views

iftop Shows Lots of Mysterious Connections - Not Showing in netstat

I've just stopped all pretty much all services except sshd on my server (Ubuntu Server 10.04), and when I run iftop I get output that looks like this: 12.5Kb 25.0Kb ...
2
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1answer
6k views

How do I configure a USB ethernet adapter under CentOS 5.3?

I've got a server running CentOS 5.3 (Final; kernel version 2.6.18) which I need to add a 2nd NIC to, initially temporarily, but eventually permanently. I'm not familiar with installing drivers under ...
2
votes
2answers
395 views

Why packets sent through libpcap are filtered out for the local host?

I have some simulator software running on linux (linux_host) in which is another linux (linux_sim) is running. The simulator uses libpcap to access the ethernet to provide network simulation on ...
2
votes
1answer
811 views

ubuntu/linux vpn connection with certificate

I want to connect to a windows pptp vpn server which accepts only connections with a CA certficate. From windows im able to do it easily (since its windows of course and native supported) but from my ...
2
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1answer
485 views

Can LRO be disabled using ethtool?

My NIC driver does not support H/W LRO but emulates LRO in the driver. Now GRO (which is a linux network stack feature) can be disabled using 'ethtool -k ethx gro off'. Is that available for LRO as ...
2
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2answers
198 views

“Symbolic link” for NICs under Linux?

Currently on my Linux server I've enabled bridging so that I can use OpenVPN in bridged mode. Works great. eth0 is connected to the LAN; tun0 is the OpenVPN gateway; these are bridged to a new ...
2
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0answers
52 views

How to route traffic through different interfaces based on the port number?

iptables -A PREROUTING -i usb0 -t mangle -p tcp --dport 8080 -j MARK --set-mark 1 iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain ...
2
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1answer
182 views

Passing through RDMA network devices to docker containers

I'm wanting to passthrough infiniband to a docker container so that I can run some high performance apps over ipoib and use rdma. Currently, I'm doing this with xen virtual machines. Now I'm looking ...
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0answers
30 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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3answers
2k 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 ...
2
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0answers
27 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 ...
2
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1answer
227 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 ...
2
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0answers
2k 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 ...