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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Setup a switch at home which acts as an extension of my office over VPN with transparent bridging

Basically, at home I have a system with 2 NICs. 1 is the my normal home network, and over this I will run vpnc to connect to my work PC (both run Linux). What I want is that the second NIC on my ...
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1answer
695 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 ...
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3answers
638 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 ...
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3answers
348 views

How do you deal with malicious IP's?

I'm trying to figure out how to protect my server against what it seems to be a botnet (I'm just guessing) Everyday, more and more IP's fill my application logs with invalid request (eg: GET requests ...
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4answers
4k 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
2k views

ubuntu forward port to another machine

I'm migrating servers, and I'd like to forward port 80 on my existing machine to port 80 on the new machine while DNS switches over. I'm running Ubuntu 10.04 server and trying to follow the guide at ...
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1answer
54 views

Choosing right computer cluster components

Recently someone at university gave me a task to create a network for parallel computing. For now i've got two intel chassis, two quad-core processors each, but it will expand with time for sure. I ...
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3answers
3k views

How to enable TCP for DNS resolution?

I've been doing some reading about this, according to what I understood this is possible, but HOW??, I know UDP is much much better for DNS resolution but because of so many issues an restrictions, ...
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1answer
400 views

Tuning network stack buffer size on GNU/Linux

Here is an excellent howto for tuning buffer size. I have a Ubuntu installation with 2.6.30+ kernel. Are those changes required or will they boost performance on the kernel I have? I am asking this ...
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2answers
21k views

How can I increase the value of somaxconn?

I can check its value by cat /proc/sys/net/core/somaxconn, is it OK if I change it simply by echo 1024 > /proc/sys/net/core/somaxconn?
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1answer
291 views

openvpn: network and ports

I've managed to setup openvpn in a test server, configuring the PKI and distributing certificates to test client machines. I can ssh from the client machines to the openvpn server using the IP of the ...
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3answers
406 views

using bgp without owning ASN

Is it possible to use BGP to announce serving IP addresses without owning an AS number? Aim is to adding another WAN provider and increase redundancy with the ability to announce IP addreess from to ...
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2answers
466 views

How can I run a DHCP client in linux when the link becomes active?

I am working on an embedded system running Linux. There is a USB ethernet adapter that can be attached to this system for debugging purposes. I would like this adapter to automatically request an IP ...
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3answers
5k 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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1answer
1k views

How to change netmask with iproute2?

With ifconfig we can change the netmask with the folowing: ifconfig eth0 netmask <new netmask> How can we do this with the command ip? I know ifconfig is deprecated and this mostly why I ...
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1answer
214 views

losing connectivity in Linux with Dell blades and such

So we have some dell blades and chassis (blades are M600's, chassis M1000's) and other systems (R710 with MD3000 array). The R710 exports a source tree via nfs for the blades to build and test with. ...
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1answer
4k views

Netcat - Listen for Multiple UDP Connections

I'm trying to use netcat to debug SIP calls, which communicate over UDP. Is there a way to get the same netcat instance to listen to multiple UDP Connections? I've tried connecting to the same netcat ...
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2answers
2k views

ssh connection keep disconected , how to find way? in CentOs vmware

Hello i have CentOS installed on vmware , few days ago every thing was working fine. today every time im connect with putty to the CentOs server after few minutes it disconnect me , how can i find ...
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5answers
8k views

What network loads require NIC polling vs interrupts?

Does anyone have some data or basic calculations that can answer when frame coalescing (NAPI) is required and when a single interrupt per frame is sufficient? My hardware: IBM BladeServer HS22, ...
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1answer
273 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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1answer
341 views

Debian: 2 network devices on the same network

I have a host running virtual machines using KVM. Each additional IP I get from the hosting company is bound to a specific virtual MAC address and will only work with this MAC (their router ...
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2answers
1k views

How do I access my WAN IP internally according to my existing iptables port forwarding rules? [duplicate]

I have IPTABLES newly set up on my Debian Squeeze server and I have IP masquerading and port forwarding working successfully with it, however if I type into the URL bar my WAN IP or DynDNS hostname, I ...
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1answer
46 views

syncing data in local using external interface

We have simple setup of firewall/gateway at out office using iptables. The public IP address is on eth2 and eth1 is local ip address (local static) and it runs dhcp server on it. Normally we keep some ...
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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

Trixbox CentOS Default GW Problem (Multi-homed server)

I'm having an issue with a CentOS trixbox server which is dual-homed (one private facing NIC [eth1], one internet-facing NIC [eth0]). I can't seem to get the default gateway to set properly to our ...
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3answers
4k views

How to completely disable IPv4 stack from Linux?

How can I disable IPv4 stack from Linux ? I want to do that dynamically, ie. sometimes I want it enabled and sometimes I want only IPv6 stack. Is there any portable way to do that ? If you know how to ...
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1answer
928 views

Implementing IPv6 Anycast

I'm trying to create a small IPv6 anycast network with 4 PC's [running CentOs 5.0, and called PC1-PC4] and two Cisco 2800 series routers. The setup is this: PC1,PC2 will be on the subnet 2001::0/127 ...
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3answers
42k views

Why ip route add doesn't work, but ip route add with less details and then change works?

I have a problem with ip route add. Surprisingly, I can add the route then change it, but I cannot directly add it: # ip route add 192.168.0.0/16 via 192.168.255.254 src 192.168.1.101 RTNETLINK ...
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1answer
119 views

Need help on setting up a small network

Please refer the image at http://oi51.tinypic.com/1zd6r9h.jpg We are about to setup a new network for our lab and following are the servers we are thinking of having File server (Samba) SVN ...
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2answers
1k 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
1k 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 ...
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2answers
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Linux e1000e (Intel networking driver) problem with resume and pcie=off [closed]

This question is a continuation of this one. I've been having a ton of problems with my Ethernet chipset and e1000e driver: 02:00.0 Ethernet controller: Intel Corporation 82573L Gigabit Ethernet ...
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1answer
541 views

Bonding bonded interfaces in linux

Let's say I've got 2 physical NICs configured as a bonded interface and another 2 NICs as another bonded interface. Can these 2 bonded interfaces be bonded into a single bonded interface?
3
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1answer
2k views

stunnel: SSL-to-SSL? (for smtp/imap)

How can I configure stunnel to accpet SSL connections, and connect then to an SSL port on a different server? Here is my setup: Our ISP's server, "Mail Server", supports smtp/imap over SSL. (Not ...
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2answers
169 views

How to list all network routes between two points and select one for transmission

I have a system which is connected to the internet via a Linux router. Normally using traceroute we can check the network route the packets traveled. Is there any tool in Linux which will list all ...
4
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2answers
10k views

query TCP buffer sizes for a socket on linux

Is there any way to lookup the send/receive buffer sizes for TCP sockets? I've poked around with both netstat and ss, as well as the raw /proc/net/tcp. Lots of goodies there, including the counts of ...
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2answers
241 views

Early congestion detection

Is there any tool in Linux which will help me to detect network congestion in advance ? If it is able to tell me that a particular network is congested, how can I route my packets through a different ...
28
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8answers
72k views

how to find out mac addresses of all machines on network

Is there some easy way to find out mac address of all machines on my network rather than doing an SSH into each and ifconfig | grep HWaddr if there are 300 machines on network I really need some easy ...
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2answers
80 views

Mounting a partition on diffrent windows machine to another linux machine

I have two different machines one is windows 2003 server and other is linux cent os 5.4. Both are on the same network. Is there any way that I can mount (network mount) windows 2003 hard drive (NTFS) ...
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1answer
190 views

local ports range redirection to corresponding addresses range using iptables

So i have this linux router, that has 2000 differents ips. And i want to redirect local source ports between 10001 and 12000 linearly from source addresses in the subnet 192.168.0.0/21 So that would ...
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1answer
1k views

Check packet vlan tag using Tap virtual interface

I am trying to learn how to implement virtual interfaces using the Tap driver. So far my understanding is that using the tap driver I can create a virtual interface and then have a userspace program ...
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2answers
2k views

Bind apparently receives responses from queries but then does nothing with them

Basically, I'm attempting to set up a DNS server that points to two other internal DNS servers. Internal DNS servers: 192.168.0.4 // 192.168.0.5 My box: 192.168.97.6 .. name is kerrigan.zipp I've ...
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2answers
2k views

dynamic routing between openvpn tunnels

i'm thinking about using dynamic routing [ OSPF or RIP ] via OpenVPN tunnels. right now i have few offices connected in full mesh, but this is not scalable solution as we add more locations. i would ...
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1answer
12k views

NAPI vs Adaptive Interrupts

Could anyone please explain how two following technologies are used to mitigate interrupt overhead under high networking load? Adaptive-rx/Adaptive-tx, and NAPI; I would appreciate an answer that ...
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2answers
1k views

How can I use Hping for OS detection?

I want use Hping for detecting Host operating system but I can't find how can I do this? I can do the same job with Nmap like this: nmap -O Host_IP/Name
5
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2answers
9k views

Using iptables to block ALL outgoing traffic from one NIC?

I must pretty bad at Googling as this seems like a very basic question but I can't seem to find the answer anywhere... and man iptables is a very long read! I have two NICs - eth0 and eth1 - on a ...
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2answers
2k views

Adding ip address to a bridge interface

Is there really any meaning attached for assigning a IP address to a bridge interface. Note : the bridge is created using brctl and then an IP address is assigned to br0 created. Is there any ...
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1answer
69 views

Does Cloned VM use the same Hard Disk space of Guest?

if i clone a guest VM in RHEL6 does the clone use the same Hard disk space of the guest? The aim is not to, as each guest VM, cloned or the normal guest should have it own hard disk space allocated. ...
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4answers
13k views

Is it dangerous to change the value of /proc/sys/net/ipv4/tcp_tw_reuse?

We have a couple of production systems that were recently converted into virtual machines. There is an application of ours that frequently accesses a MySQL database, and for each query it creates a ...
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2answers
677 views

Iptables Forwarding problem

I had initally asked question about sertting up my linux box for natting for my home network and was given suggestions in the thread here. Did not want to clutter the old question so starting a new ...