Routing (in IP-based networks) is the process of selecting paths in a network along which to send network traffic.

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29
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2answers
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Reply on same interface as incoming?

I have a system with two interfaces. Both interfaces are connected to the internet. One of them is set as the default route; a side effect of this is that if a packet comes in on the non-default-route ...
26
votes
1answer
30k views

What is kernel ip forwarding?

I have seen on many blogs, using this command to enable IP forwarding while using many network security/sniffing tools on linux echo 1 > /proc/sys/net/ipv4/ip_forward Can anyone explain me in ...
23
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3answers
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what is the meaning of 0.0.0.0 as a gateway?

Can anyone clarify gateway assignment for me? What is the difference between adding gateway as 0.0.0.0 and assigning a specific ip address as a gateway?
20
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2answers
30k views

Use ssh with a specific network interface

I'm using openconnect to connect to vpn. After entering my credentials, I get this: POST https://domain.name/... Got CONNECT response: HTTP/1.1 200 OK CSTP connected. DPD 30, Keepalive 30 Connected ...
15
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3answers
43k views

Output traffic on different interfaces based on destination port

My question is basically the same as Only allow certain outbound traffic on certain interfaces. I have two interfaces eth1 (10.0.0.2) and wlan0 (192.168.0.2). My default route is for eth1. Let's say ...
15
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3answers
2k views

Can I limit a user (and their apps) to one network interface?

As the title really. I've actually got two scenarios to apply this: Multiseat Desktop: two network connections both with internet gateways and two accounts doing bandwidth-intensive tasks on each. I ...
13
votes
3answers
4k views

scp between two servers not in the same network

There are two server that I can access with 2 different VPN connections. I have managed to have both VPN working on the same time on my machine (a bit of routing rules). I want to do a scp <...
13
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4answers
15k views

How to find out which interface am I using for connecting to the internet?

I have eth0 and wlan0 according to ifconfig and I can ping google.com. How can I find out (with a normal user, not root) what interface is active, as in, what interface did the ping (or whatever, ping ...
12
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2answers
14k views

How to refuse routes that are PUSHed by OpenVPN server?

When I establish an OpenVPN client connection over the Internet to our corporate OpenVPN server, it pushes several static routes. Unfortunately, these routes break some connectivity within my local ...
12
votes
1answer
10k views

Linux as router with multiple internet providers

Linux as router: I have 3 Internet providers, each with its own modem. Provider1, which is gateway address 192.168.1.1 Connected to linux router eth1/192.168.1.2 Provider2, gateway address 192.168.2....
11
votes
7answers
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How can I change the default gateway?

Currently I'm running a FreeBSD 9.1 and the default gateway is already configured in the rc.conf. rc.conf: defaultrouter = "10.0.0.1" But now I want to change the default gateway without rebooting ...
10
votes
2answers
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iptables --set-mark - Route diferent ports through different interfaces

Short story, 3 interfaces, eth0 (LAN), eth1(ADSL), eth2(4G). eth0 -> eth1: Works (ports 80, 443, 4070) eth0 -> eth2: Doesn't happen This is a graphical representation of the idea: Port 80 & ...
9
votes
2answers
4k views

Bind unix program to specific network interface

Question: How do I launch a program while ensuring that its network access is bound via a specific network interface? Case: I want to access two distinct machines with the same IP (192.168.1.1), but ...
9
votes
5answers
18k views

How to route specific adresses through a tunnel?

There are certain websites/services which I can only access from the subnet on which my server is located (think of the typical intranet scenario). Is there a way to transparently route traffic that ...
9
votes
1answer
3k views

Change remote host IP address without losing control (Linux)

How can I change a remote host primary IP address without getting disconnected at all (without being in a "no IP addr" state). The matter is poorly discussed on Internet (according to my research). ...
8
votes
5answers
63k views

How to remove all default gateways

I'm running a custom built linux machine, so not all linux commands are available. I execute network related commands, so I need to set a default gateway right before I run my command, then remove ...
8
votes
1answer
2k views

Dual network connection

I have a usb cellular modem and a Home LAN connection on my Ubuntu 10.10 box. Both work independently. I want to know how to have both connected at the same time, and be able to specify which ...
8
votes
1answer
7k views

Routing public ipv6 traffic through openvpn tunnel

What I'm trying to do is to route IPv6 traffic through a vpn tunnel. That way, I should be able to use IPv6 in a network that doesn't support IPv6. I have a VPS which has an IPv6 block assigned. Part ...
7
votes
2answers
7k views

How to build a gateway from my Linux OS

I want to configure my Linux so that it will be used as a network router (gateway). Can anybody give me some hints on this? (links are welcome!)
7
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1answer
1k views

Linux routing for receiving packet

Maybe this is a dumb question. I have two NIC and they are in the same subnet. ip route commnad show above. Kernel was build WITHOUT policy routing. My question is: When receiving packet whether ...
7
votes
2answers
5k views

Network interface preference

How does Linux determine which network interface to use, when both are connected to the same network? Note that this isn't a question on routing. I'm familiar with how that works. This is if, say, I ...
7
votes
2answers
2k views

1:1 NAT with several identical LANs

I want to connect several LANs located on remote buildings. The "central" site have a Linux computer running OpenVPN. Each remote site also run OpenVPN. the central site has a LAN numbered 192.168.0....
7
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2answers
3k views

linux multiple internet connections load balancing with fail handling

I have two ISP connections and need automatic load balancing between them. I also need to handle failed connections (not use one that does not work). First link is a PPTP connection (ppp0), second is ...
7
votes
3answers
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How can I disable automatic IPv6 neighbor route advertisement on a router?

I work for an ISP that's in the process of making its infrastructure IPv6-ready. Our core routers already have a working setup, but a large portion of our fiber customers are behind a router running ...
7
votes
1answer
2k views

What do I need to add a virtual IPsec adapter?

I'm trying to set up an IPsec connection manually from the console with iproute2. What I need is a virtual interface (at best, a virtual IP address could also be sufficient) that IPsec-transforms ...
6
votes
1answer
7k views

Using the Wifi of a notebook via ethernet for another PC

I want to connect a PC to the internet via my notebook, which is connected to a WLAN. The setup should look like the following scheme: PC (eth0) -> Notebook (eth0) -> Notebook(wlan0) -> ...
6
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1answer
60k views

Adding two default gateways in Debian interfaces file

This is my interfaces file: auto eth0 iface eth0 inet static address 192.168.1.10 netmask 255.255.255.0 gateway 192.168.1.1 auto eth1 iface eth1 inet static address 192.168.2.10 ...
6
votes
1answer
38k views

OpenVPN: Push a route to client with a different gateway

I would like my OpenVPN server to push a route down to the client with a different default gateway. Specifically, my OpenVPN server has an internal IP address of 10.0.0.1, and I would like it to ...
6
votes
4answers
7k views

Trying to connect to gateway in static ip network

I have arch-linux-arm running on a raspberryPi. The network I am in uses static IPs. gateway IP is 192.168.178.5 IP for my device is 192.168.178.201 To connect to the internet I use: ip addr add ...
6
votes
1answer
1k views

Skip routing via `lo` interface for outgoing packets

Introduction I have following load balancing configuration: 10.0.1.31 - lb 10.0.1.35 - virtual IP 10.0.1.32 - node1 (tomcat + mysql) 10.0.1.33 - node2 (tomcat + mysql) I'm using keepalived which ...
6
votes
2answers
4k views

What is the interface scope (global vs. link) used for?

Routing table entries have an attribute scope. I would like to know how the change from global to link (or the other way round) affects the network system.
6
votes
2answers
307 views

Looking for elegant iproute2 solution for host w/ 2 interfaces on 2 networks and 3 gateways

I've got a Linux webserver with 192.168.0.2/24 assigned to eth0 and 172.16.0.2/24 assigned to eth1. I must not change this. Here's the routing so far: 172.16.0.0/24 dev eth1 proto kernel scope link ...
5
votes
3answers
4k views

ssh will sporadically hang temporarily on fast connection

I am using Ubuntu 13.04 on my laptop, connected to my router at home. When working from home, I will ssh into the servers on campus, through a vpn, with X11 forwarding. ssh -X server.address.on....
5
votes
2answers
1k views

Route and “e” flag

k# route -6 Destination Next Hop Flag Met Ref Use If ::/0 fe80::8001 UGDAe 1024 0 0 eth0 [...] What does flag "e" mean?
5
votes
1answer
1k views

What is the routing behaviour when two or more default routes?

I have two ISP at the time, connected to the same machine. I added both of them in the routing table as default. However, only one connection is used. $ route Kernel IP routing table Destination ...
5
votes
2answers
15k views

Linux Networking routing to virtual ip addresses from a different subnet

New to linux networking, had a question about routing to virtual ip addresses from a different subnet. I have three servers (they can all ping each other): A 10.10.51.182 (connected to router Y)...
5
votes
2answers
932 views

How can I use Linux as a Gateway?

NOTE: If client devices (computer B in this example) want to obtain internet through the gateway computer, maybe they still need to configure nameserver resolution. This is not explained here (a ...
5
votes
1answer
3k views

Internet routing between wlan0 and ppp0?

On my Debian Linux device, I have a USB-modem that is connected to the Internet. Its interface name is ppp0. I also have a USB-wireless adapter, where I am hosting a Access Point. Its interface name ...
5
votes
2answers
4k views

Routing for multiple uplinks/providers

I have a PC with two internet connections. The first one is an Ethernet interface to connect to my local network and access internet via my router. The second one use a GSM modem to connect with ppp. ...
5
votes
3answers
2k views

Redirect traffic through vpn on an as needed basis

My problem is really simple yet it sounds complex, but I have zero to none experience with this. I have set up a box using gentoo which has its own semi-static WAN-IP and acts as router for my LAN. I ...
5
votes
1answer
4k views

Debian, two network cards - “no route to host” on eth1

I have added a secound nic in a debian box. That nic is ment for doing some test stuff, so those devices connected should just be able to access the debian box or be accessed from it. To set up the ...
5
votes
1answer
564 views

Using source routing (LSRR) - any ideas?

What I want to do is conceptually very simple, but I can't find any information or help about how to go about doing this. Basically, I want to configure my networking to use source routing (LSRR). ...
5
votes
1answer
5k views

how to understand the routing table on an OpenVPN client

I just setup the OpenVPN and it is working as expected. However, the routing table of the client is confusing me to no end. Here is the route table: # route -n Kernel IP routing table Destination ...
4
votes
3answers
2k views

Using bridge utils to connect two computers via Linux

I have been using bridge utils previously to connect my network connected computers to a single interface on my Linux computer. The problem I'm having is when I installed a new Linux (with Slackware) ...
4
votes
2answers
735 views

Why can I reach a different interface's IP address?

I'm wondering about this, and I can't seem to find an explanation on the internet. I have a linux gateway which has multiple interfaces: eth0: external ip eth1: 172.16.1.1/24 eth2: 172.16.2.1/24 ...
4
votes
1answer
31 views

How can I tell which IP address is used to connect to another machine?

I have several computers that are multi-homed, and have different static IP addresses for each of several network connections. How can I tell which of these IP addresses is used when I'm connecting to ...
4
votes
2answers
4k views

Redirect ALL packets from eth1 & eth2 through a SOCKS proxy

Is there a way to redirect all traffic, UDP and TCP, coming to and from eth1 and eth2 through a SOCKS proxy (Tor) which then passes it through eth0? eth0: Internet in - leads to the main router, then ...
4
votes
1answer
3k views

Can't ssh to beaglebone?

After I did: route add default gw 192.168.7.1 I also changed /etc/resolv.conf: nameserver 192.168.7.1 in order to share internet between Ubuntu in VMware. I've got internet working but after a ...
4
votes
1answer
7k views

How do I route traffic through specific interface for a specific process

I have a script that runs from cron every 15 minutes. The script is meant to ping my DNS server to update a dynamically changing IP. I want this script to ping through the wlan interface and not the ...
4
votes
1answer
10k views

Is route add … the best way of directing traffic through a vpn

I have set up a VPN on a remote ubuntu machine using pptp-linux and the instructions found here. After set up no traffic seemed to be going through the VPN and the VPN network devices were not ...