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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How to reduce number of sockets in TIME_WAIT?

Ubuntu Server 10.04.1 x86 I've got a machine with a FCGI HTTP service behind nginx, that serves a lot of small HTTP requests to a lot of different clients. (About 230 requests per second in the peak ...
4
votes
1answer
7k views

How to troubleshoot latency between 2 linux hosts

The latency between 2 linux hosts is about .23ms. They are connected by one switch. Ping & Wireshark confirm the latency number. But, i dont have any visibility into what is causing this latency. ...
10
votes
2answers
29k views

Linux e1000e (Intel networking driver) problems galore, where do I start?

I'm currently having a major problem with e1000e (not working at all) in Ubuntu Maverick (1.0.2-k4), after resume I'm getting a lot of stuff in dmesg: [ 9085.820197] e1000e 0000:02:00.0: PCI INT A ...
20
votes
5answers
7k views

Hostnames - What are they all about?

I've recently been "forced" to perform some sysadmin work, while this isn't something that I absolutely love doing I've been reading, experimenting and learning a lot. There is one fundamental aspect ...
23
votes
8answers
46k 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 ...
3
votes
1answer
7k views

VLAN tags not shown in packet capture (Linux) via tcpdump

I am adding a tagged VLAN onto eth0: #ip link add link eth0 name eth0.20 type vlan id 20 This results in: #ip link 2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc ...
2
votes
1answer
1k views

Port appears open locally but closed from another machine

I am currently trying to set up a Hadoop distributed compute cluster on my network. Currently. my cluster nodes are encountering a problem communicating with my master server. Right now I am working ...
2
votes
1answer
235 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 ...
1
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1answer
1k 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 ...
0
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2answers
3k views

How to route UDP traffic from one public IP (linux) to another public IP(Windows)

I want to prevent direct access of my Windows Machine and want to expose some programs running on it via my Linux Machine (which again is accessible by a Public IP). Is there a way where-in I can ...
2
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1answer
471 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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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 ...
1
vote
1answer
593 views

Adding a whole IPv6 /64 block to an network interface on debian

I tried adding a whole IPv6 (/64) block to an interface using ip route add local 2001:41d0:2:ad64::/64 dev lo like described here on my Debian server, but I seem to be missing something. If I ping ...
1
vote
2answers
3k views

AWS VPC + IPtables + NAT: Port Forwarding is not working

Yesterday, I posted a question here but I think was not clear enough in my words. BTW, This question is not a duplicate. I have AWS VPC Setup as below. GOAL/PROBLEM: SSH to Server A from internet. ...
0
votes
1answer
4k views

Openvpn - enabled redirect gateway but can't access any websites

First of all I'm a newbie to servers but not to stuff like programming so not totally alien to command lines etc. Second, I want to run openvpn on my remote server and connect from my ubuntu desktop ...
10
votes
4answers
15k views

multiple MAC addresses on one physical network interface (linux)

Simple question: How can I setup multiple MAC addresses on one physical network interface (linux)? Why? My ISP is checking ip<->mac on GW and I d like to route traffic through my "linuxbox" and ...
10
votes
4answers
2k views

tc u32 — how to match L2 protocols in recent kernels?

I have a nice shaper, with hashed filtering, built at a linux bridge. In short, br0 connects external and internal physical interfaces, VLAN tagged packets are bridged "transparently" (I mean, no VLAN ...
3
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1answer
3k 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?
10
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1answer
5k views

PXE Booting Virtualbox guests in internal networking mode?

I am not sure if this is just specific to my distro's packages or is a vbox limitation. So, any help would be appreciated. Ok, so I have a network of VMs, with one VM acting as a NAT for the other ...
4
votes
1answer
8k 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 ...
4
votes
5answers
6k views

Override DHCP hostname on RHEL5/CentOS/Amazon Linux

I'm running Amazon Linux (based on RHEL5) on EC2. I have my own domain name pointing to the instance's elastic IP. Amazon auto-assigns the instance a generic (and not visible on the Internet) ...
3
votes
2answers
1k views

Cheap way to detect client round trip times for http

I am trying to figure out a way to detect round trip times for each IP that connects to port 80 on my server. What is a good way to do this? There are far to many connections, and pinging each ip is ...
4
votes
2answers
5k views

How do I put a bridge on top of a bonded interface?

I'm setting up a Ubuntu Server 11.10 box with multiple Ethernet interfaces that are bonded for redundancy. I'm planning to use it as a KVM host, so I'll need a network bridge. To accomplish this, I ...
3
votes
1answer
7k views

Checkpoint VPN on Linux

I need to setup a Checkpoint VPN client with a customer who gave me these settings: Authentication Type: P12 certificate Password: * Peer Site: IP_ADDRESS They tell me the VPN server is: IPSO ...
2
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2answers
655 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 ...
2
votes
2answers
410 views

Using linux server as router for network

I would like to setup my Debian Lenny server as a router for my home network using iptables, but so far have been unsuccessful. Below is a diagram of the desired network architecture INTERNET - ...
1
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1answer
1k views

bridging two network interfaces in ubuntu linux 12.10 AND being able to access it from that machine

Ok, i have about had it but heres the deal. I have 7 total machines connected like this: [5 workstations]<--->ServerPC<---->MAINPC<---->router FYI, dont worry about the workstations they ...
1
vote
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 ...
1
vote
2answers
3k views

Get linux to change default route if one path goes down?

I'm configuring a gateway/router linux box. It is performing masquerading/NAT. The primary Internet interface is a 3G modem, but if that goes down, I would like it to try a different interface ...
1
vote
1answer
169 views

Setting up NTP on 2 Linux boxes and one OpenBSD box

I have been tasked with getting an NTP client working on two Linux machines and an OpenBSD machine. The machines are arranged like this: NTPServer / \ / \ L1 L2 ...
0
votes
3answers
1k views

Configure gateway for two NICs through static routeing

OK I have two NICs eth0 and eth1. Each over their own default gateway. I can only access the network on eth0 since that is the first NIC to have a default route added. How can I configure my static ...
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1answer
521 views

How can I stop Linux from sending ICMP “Destination Unreachable” responses? [closed]

I have a Linux system which has a number of services disabled (for example, telnet). When a telnet client attempts a connection, the system responds with an ICMP "Destination Unreachable". Is there ...
7
votes
5answers
15k views

Can only bring up one of two interfaces

I'm having a bizarre issue with my HP Proliant DL 360 G4p server. It has two gigabit ethernet interfaces but I can bring up only one of them. This is starting to freak me out and that's why I turned ...
3
votes
4answers
3k views

How to persist ethtool settings through reboot

I would like to turn off tcp segmentation offload on a CentOS5 server. Using ethtool the command is ethtool -K eth0 tso off However, this setting only persists for this session. How can I make it ...
3
votes
2answers
498 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 ...
2
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2answers
3k views

iptables and multiple ports

This doesn't work for me: # iptables -A INPUT -p tcp --dports 110,143,993,995 -j ACCEPT iptables v1.4.7: unknown option `--dports' Try `iptables -h' or 'iptables --help' for more information. ...
2
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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 ...
2
votes
2answers
890 views

Linux IPv6 loopback routes getting automatically added

We have a router running Debian Lenny that has been happily routing IPv6 for several months. Our upstream has advised that our address range is changing, and both are currently operational, so I ...
1
vote
1answer
396 views

Service httpd restart error

Why do i always get the error when ever i reset my httpd: Starting httpd: (98)Address already in use: make_sock: could not bind to address [::]:80 (98)Address already in use: make_sock: could not ...
1
vote
2answers
913 views

Intel igb driver packet loss on Debian Linux 6.0

I am running Debian Linux 6.0 (2.6.32-5-amd64). My network NICS are Intel 82580 Gigabit running with the IGB network driver version 3.3.6 (firmware version 3.2-9). I tested the performance and I ...
1
vote
3answers
572 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 ...
1
vote
2answers
613 views

redundant network handling in linux box

I need your help very badly. I have give a solution for the requirement. I'm struggling for 5 days to get one. Requirement is to get a solution for redundant network in Linux systems. We have ...
0
votes
1answer
47 views

Using Firewall-cmd to create address specific restrictions in centos 7

How do I create a firewall rule using firewall-cmd tool (new firewalld) such that I will limit specific network to access only one service and allow all on all service in one zone. For example: I ...
0
votes
0answers
46 views

getting rid of unused listening ports (kernel)

As a follow-up on this question, I have that issue (ports that are reported listening in netstat, but have no process linked to it) and it's the nlockmgr that's actually using these ports according to ...
0
votes
2answers
230 views

IPtables: Forward port to another host is not working

I am trying out something so this is my test setup: Setup: I have AWS VPC with a public and private subnet. I have a host in public subnet with a public IP address (say Host A) I have a host in ...
0
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1answer
263 views

Setting the default network interface

My /etc/network/interfaces looks like this: auto lo iface lo inet loopback auto eth1 iface eth1 inet static address 10.0.0.99 netmask 255.255.255.0 gateway 10.0.0.1 auto eth0 ...
0
votes
1answer
3k views

Sub-interface already in use on another host - brand new interface

I created a sub-interface on a RHEL box, eth0:1, and copied the eth0 config and changed all the settings to reflect eth0:1 and the IP address. However, when I issue ifup eth0:1 I receive this error: ...
0
votes
2answers
566 views

How to set a custom route source in openvpn

I have a simple openvpn configuration. remote 1.2.3.4 dev tun ifconfig 10.74.1.13 10.75.2.1 secret static.key route 10.75.0.0 255.255.0.0 keepalive 10 60 When the link come up, the routing table is ...
0
votes
1answer
2k views

Can't connect or ping to internet from my device using crossover ethernet [closed]

I followed this post to connect my Raspberry Pi (an ARM-based computer) to my PC via crossover cable to use wifi connection of my PC (openSUSE 11.4): (UPDATE: now I have openSUSE 12.1) ...
0
votes
2answers
1k views

Hosting websites on a public ip routed via a private subnet using one Linux machine as both router and server

I use Ubuntu server as router, NATing router and webserver. The server is connected to ISP with a public /29 subnet. Also I host some important websites on it. I asked the ISP to provide ipv6 address ...