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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1answer
777 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
989 views

ksoftirqd hitting 100% on interface with ixgbe driver

This is my driver information. ethtool -i ethXX driver: ixgbe version: 3.9.15-NAPI firmware-version: 0x800000a5 bus-info: 0000:04:00.0 supports-statistics: yes supports-test: yes ...
2
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1answer
366 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
2k views

What is the difference between MULTICAST and ALLMULTI ifconfig ifconfig flags

What is the precise difference between the ifconfig flags MULTICAST and ALLMULTI? Also How do I change the default flags under Ubuntu?
2
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1answer
986 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
4k 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
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2answers
330 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
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1answer
640 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
372 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
194 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 ...
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0answers
14 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
38 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
votes
1answer
24 views

Is the ethx mac address of a VM the same as the mac address of the corresponding tap interface?

I have a single node openstack install on an ubuntu machine. For some reason that I cannot figure out, the linuxbridge is dropping packets from this VM. My iptables seem to be fine (atleast as far as ...
2
votes
0answers
263 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 ...
2
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2answers
189 views

Redundant Iptables Routers - secondary router logging martian packet errors

We have a network mostly set up with a redundant pair of Linux Iptables firewalls/routers, but we're missing a crucial piece of the puzzle. Any local traffic destined to the secondary router succeeds ...
2
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1answer
92 views

Unable to discover other systems in lan - centos 6.4

I have 4 servers, 3 old and 1 new, and each of them are connected via vlan through eth0 and eth1 is used for internet. Three of the servers are working fine and able to communicate with each other. ...
2
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1answer
141 views

Software to prevent daemons from binding/listening to local ports?

Having an issue with some not-so-bright developers creating daemon processes that are binding to the (not actually reserved) local ports on our Linux servers. Those ports being defined in: cat ...
2
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1answer
316 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
votes
1answer
124 views

Unable to connect to Internet in OEL5 guest even though I can ping machine from host machine

I have Oracle Enterprise Linux 5 as Guest on VirtualBox running on Windows 7 host using Bridged Network. I have being trying to configure a static IP on OEL5 VM Guest at work, as previously the VMs ...
2
votes
1answer
163 views

Bandwidth fluctuations while running java server

We are running a distributed system of java servers (os: linux) doing lot of computation with communication over TCP. While our traffic pattern in not bursty, on some machines we see a fluctuation in ...
2
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2answers
125 views

NAT, iptables and problematic ports

I am building a small office network with virtual machines. My schema is this: Computer A: gateway, ip 1.1.1.1, iptables used for NAT [eth0=public internet dhcp, dhcp; eth1=gateway] Computer B: ...
2
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1answer
217 views

MTU value causing applications to hang

I am using CentOS 5 in my environment and it acts as a gateway for my LAN. My eth0 interface MTU is set to 1500 (default). UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Recently I am facing a ...
2
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1answer
169 views

open source solution to a gateway for a network of a housing cooperative of 150 people

i just inherited a barely functioning network for a student housing cooperative of about 150 people. in it's current state, as i understand it from the previous person in charge of the network, we ...
2
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1answer
374 views

qemu with tun virtual networking issues

I'm trying to setup a virtual networking environment using open-wrt qemu and vde2 The script to boot two qemu instances and conenct them together is the following ...
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0answers
368 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 ...
2
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1answer
431 views

Apache2/Shibboleth TCP connections stuck in CLOSE_WAIT

I run an Apache2 server which uses the Shibboleth daemon (shibd) as federated authentication module. Certain server connections using Shibboleth seem to stick permanently in CLOSE_WAIT state. tcp ...
2
votes
3answers
409 views

Load balancing for webservers (with state sync)

(I've looked at other questions, I don't think any of them cover the same stuff as this) I'm looking at a load balancing solution for our farm of webservers. We currently use Cisco CSS11000 series ...
2
votes
1answer
206 views

complicated bonding and network question

I am not a network guy and would like to know how can I setup the below two configurations and their pros and cons: Networking component: -- WAN: Cisco 2970 * 1 Load Balancer: F5 switch 1600 * 2 ...
2
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1answer
727 views

bridge traffic limiting via tc

I have a Linux machine running as a bridge simulating various network conditions. I use tc for this. Introducing delays or packet loss is quite simple but I got into trouble trying to configure ...
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2answers
801 views

Accidentally set .255 IP address - how can I ssh to the machine?

A server's static IP address got set to x.x.x.255 on a Windows network, but apparently .255 addresses are broadcast addresses to windows. So now I can't connect to the box from my Windows machine. ...
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2answers
2k views

Difference between /etc/hosts and /etc/resolv.conf

What is the difference between /etc/hosts and /etc/resolv.conf? Also, is there a good documentation that explain all these configuration files. Thank you. Bala
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3answers
2k views

Bridging two Ethernet networks /w DHCP over WiFi

What I am looking for is a bridge. WiFi cannot handle normal bridging, so how can I route two IP Ethernet networks using WiFi? (Under Linux) How do I set up IP routing under Linux? It must forward ...
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2answers
940 views

MAC Address of device when turned off?

Is it possible to get a list of MAC addresses of devices connected to a network, even though the device is currently turned off? The device has power so I could do a wake-on-lan. I'm trying to get ...
1
vote
4answers
1k views

How to change persistent-net-generator.rules to be PCI bus dependent and not MAC based?

I am using CentOS 6.2 with VMware. I often have to clone my systems. Every time I clone it is adds a new rule to 70-persistent-net.rules file like so. SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ...
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5answers
3k views

How to make ALL ports accessible on CentOS 5.6?

I've set up a CentOS 5.6 development server running as a virtual machine under Virtual PC 2007, in order to have a play with Node.js. Everything is up and running, but I can't seem to access port ...
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3answers
3k views

What is this eth0.bak?

Why do I have 2 of the same devices but different nicknames? Do I need to delete one? What is with this eth0.bak? Thanks for any advice. =) BTW, this is from RHEL virtual machine in case that ...
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2answers
456 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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2answers
48 views

Is it necessary to specify server ip in the destination option of the iptables rule?

I use iptables to log all incoming connections. While going through the log in var/log/messages, I notice that there are some incoming connections from another computer to an unassigned LAN ip ...
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5answers
211 views

Finding malicious network usage in a LAN

I manage a small LAN (30 computers, mix of Linux, Windows, and Macs). Transferring a 100MB file to a local server (i.e. in the office, not on the Internet) used to take me about a couple minutes, but ...
1
vote
3answers
493 views

forward port 3306 from firewalled machine to desktop using SSH?

Here's the network setup: Machine A (my PC) SSH 22 => Machine B (Linode with root access) SSH 21343 => Machine C (MySQL server). I want to forward port 3306 from C through B to A, so I can use SQL ...
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3answers
519 views

Detect devices connected to my network

Another day, another question ! I am trying to write a script that would monitor my LAN for any new new devices connected to it and if it finds a new device, send me an email. My test network is a ...
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3answers
134 views

Network setup help

I'm going to set up a network that looks like this: There is no Internet connection, i.e. this is a closed network. There will be one Ubuntu 10.04 server (64-bit) that handles all the services ...
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2answers
61 views

Red hat reporting more NICs than are physically present

We just deployed several servers (hp dl360p g8), and after the initial boot we're noticing that none of the network devices are showing up as cabled. Ethtool shows no link anywhere. Even more weird is ...
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vote
2answers
1k views

How virbr0-nic is created?

How can I create virtual network interface like virbr0-nic? I am trying to find a way to create NIC like virbr0-nic but everything which I can find in internet is how to create interface attached to ...
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vote
1answer
777 views

how to setup subdomains for AWS EC2 Ubuntu Instance?

I am trying to setup subdomains for my AWS EC2 ubuntu instance, but without enough knowledge I couldn't proceed anymore. I have a parked domain name example.com on a domain name service provider. My ...
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2answers
667 views

debian: standard outgoing IP / route

On a debian squeeze server I got 2 IPs on eth0 (eth0 and eth0:1). When opening TCP connections the server uses the eth0:1 IP by default. However I want it to use the primary (eth0) IP because I want ...
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3answers
3k views

How to formulate IP forwarding rule using iptables

I have two Systems A and B. A is a TCP Client and sends a message to TCP Server on B. ------------------ -------------------------- System A System B ...
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2answers
242 views

openvpn create route once the tunnel is established

I want to have access to my office LAN from my private server I have successfully set up a VPN tunnel between my private server and my computer at my office using this link. I can for instance ping ...
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1answer
259 views

What is the difference between these two network configuration files?

/etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network The contents are similar, why the need for two files?
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2answers
596 views

Share an internet connection with Debian

Here's my current /etc/network/interfaces file on the "server": auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp name Wired Network auto ath0 iface ath0 inet static name ...