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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29
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2answers
44k views

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 ...
5
votes
1answer
2k 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 ...
7
votes
1answer
20k 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. ...
14
votes
2answers
40k 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 ...
30
votes
6answers
14k 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 ...
5
votes
4answers
1k views

Transfer large amount of small files

I've to do a migration of two servers with large SAN attachments to our new VMWare environment. EDIT: I have to supply some additional intelligence as I have good answers regarding VMWare solution. ...
5
votes
3answers
8k 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. ...
28
votes
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 ...
13
votes
4answers
28k 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 ...
9
votes
1answer
11k 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 ...
11
votes
1answer
28k 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 ...
3
votes
3answers
218 views

Iptables rules with ! character

I have entered iptables rules to log a specific connection on our server, but it doesn't seem to be working as I want it to. Here are the rules: 1 LOG tcp -- !10.51.0.0/16 ...
3
votes
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 ...
2
votes
1answer
3k 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
263 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
votes
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 ...
0
votes
2answers
7k 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 ...
3
votes
2answers
214 views

Apache webserver & Tomcat : Runing multiple tomcat webapps and apache webserver app at same time

We have a Debian X64 server which currently has a tomcat instance where we have 3 webapps in WAR file ofcourse. Also, we have an Apache webserver, which has one CMS system running. And one final ...
2
votes
1answer
660 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 ...
0
votes
1answer
5k 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
1answer
11k 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?
11
votes
5answers
3k 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 ...
12
votes
2answers
9k 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 ...
5
votes
5answers
10k 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) ...
10
votes
8answers
74k views

Can't start CentOS 7 “network” service

I Can't start CentOS 7 "network" service after disabling and removing "NetworkManager" service. When I check the network service status, it comes up with the following error: #systemctl status ...
8
votes
1answer
21k views

How GRO (generic receive offload) works on more advanced NICs?

I am interested in particular answers: Does the NIC with GRO edits/creates TCP ACK or any other packets (or is this feature transparent to receiver/sender TCP stacks)? There should be a ...
5
votes
2answers
3k 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 ...
6
votes
1answer
8k views

Ubuntu: Network driver reset to eth0?

I've been trying to get my Ubuntu Server VM running through VirtualBox. I ended up trying several network interfaces because of some networking issues and finally got it working. However, I noticed ...
1
vote
2answers
3k views

OSPF: how to advertise the subnet of an OpenVPN server?

I have successfully configured OSPF on all of our HP ProCurve 7102 routers, and most of our internal Linux routers. Routes get advertised, and all is peachy. Except for the routes into the subnets ...
6
votes
2answers
9k 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. ...
3
votes
1answer
11k 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 ...
1
vote
2answers
7k 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 ...
0
votes
2answers
925 views

The same IP on multiple interfaces

Hello networking gurus, I've got a Linux (kernel 3.14) server which acts as a TFTP, NFS and HTTP server for a farm of consumer electronics devices (set-top boxes - STBs). The devices use TFTP to boot ...
5
votes
2answers
7k 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 ...
5
votes
1answer
14k views

PREFIX versus NETMASK

I did setup a virtual network interface in Centos 6 copying the ifcfg-eth0 to ifcfg-eth0:1 and changing the appropriate variables. But the connection was unstable. Although one of the pre-existent ...
3
votes
2answers
1k 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
1answer
2k views

Cannot ping to localhost into CentOS

I'm connecting to my server (Centos 7) with ssh and I try to ping to localhost: ping 127.0.0.1 but doesn't work: ping 127.0.0.1 PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data. ^C --- 127.0.0.1 ping ...
2
votes
2answers
417 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
vote
1answer
2k 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
0answers
625 views

VirtualBox - multiple guests, each with a single bridged adapter?

I am running a dedicated server (located at Hetzner, Germany) that runs VirtualBox in order to virtualize several services accross multiple virtual guests. Those guests are supposed to communicate ...
1
vote
3answers
7k 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 ...
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
1answer
186 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
2answers
2k 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 ...
-4
votes
1answer
913 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
7answers
13k 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 ...
7
votes
5answers
21k 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 ...
5
votes
1answer
3k 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 ...
4
votes
2answers
11k views

debian set eth0 autoneg off speed 1000 duplex full: Invalid argument

I use debian for my things,but when i config speed 1000 and duplex full the error occur the exactly command i use: ethtool -s eth0 autoneg off speed 1000 duplex full Cannot set new settings: ...
3
votes
2answers
4k views

Delete specific conntrack entries?

in a multi-ISP configuration, I'm routing and NATing specific traffic, e.g. VoIP, through specific interface - to a distinct provider. When one of the interfaces (or routes) becomes unavailable, all ...