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

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Detect which interface traffic to an IP address goes through

I'm making an script, and I need to detect in what interface is the traffic of an IP going through. This is because in the arch, an IP address is attended only for one of four NIC's, but can be any of ...
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How is the loopback network interface implemented?

The loopback network interface "is a virtual network device implemented entirely in software," according to another question on Unix.SE. But how is this implementation actually accomplished, and how ...
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Different sites on different interfaces using link aggregation

I read about Ubuntu Bonding and how it allows to bond multiple connections to get several advantages. My requirements is this : I want two different interfaces at a time (A wifi and other Ethernet) ...
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Make nslookup use specific interface

On my computer I have two network cards. Both are using different Internet Providers service. Both Internet service provider have different DNS server and their IP address are known to me. I want to ...
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How do I route web requests into my private network depending on the domain in the url?

Scenario: Due to limited number of IPs, several domains are resolved into the same IP address. However, these domains may not all run on the same webserver, VM, or even dedicated machine. Therefore, ...
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178 views

Rewrite source IP in TCP replies using iptables

I'd like to rewrite the source IP on TCP/514 traffic leaving a redhat machine, for connections that weren't initiated from the machine. The machine receives TCP/514 traffic on an interface, for ...
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749 views

routing cache in latest Linux kernels

As I understand, routing cache was removed since Linux kernel 3.6. In systems with older Linux kernel one could view the content of the routing cache with ip route show cache command and routing ...
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Bridge/Router with custom logic

I've a Linux box with 3 network adapaters, which I'd like to configure as follow: Adapter A is connected to computer A Adapter B is connected to computer B Adapter C is connected to the Internet. ...
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Forwarding packets from loopback interface with policy-based routing

I have the following iptables rule: iptables -t mangle -A PREROUTING -p udp -m udp --dport 10000 -j MARK --set-xmark 0x4/0xffffffff which sets fwmark 4 on all udp packets with destination port ...
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iptables routing incoming IP to another destination IP question

I have a test setup: server1:1.1.1.1 server2:2.2.2.2 client: 3.3.3.3 I'm trying to have client IP 3.3.3.3 do a HTTP request from the 1.1.1.1 server. However I want the 1.1.1.1 server to pass this ...
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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 ...
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How do I prevent my hostapd access point from pretending to route to the Internet?

I have a nice little iMX6 (an ARM CPU) board running Linux kernel 3.0.35 with hostapd 0.7.3. Setting up the wireless interface as an access point works fine but clients think they can be routed ...
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Route only ssh traffic through VPN

Is it possible to route a computer's SSH service through a VPN connection but allow ALL other data to exit through the WAN address? What sort of iptables magic needs to be done to accomplish this? ...
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1answer
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Linux nat/iptables configuration for a chain of peer-to-peer links

I have an experimental setup, of 4 Linux (CentOS) machines: All 4 machines are internally connected using different networks and can ping eachother directly connected interfaces. However only PC4 ...
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1answer
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Only routing certain traffic through VPN

I have a central development server, running a VPN server, and a couple clients that need to connect to it. The server is running Apache, but is only accepting local requests (only listening on ...
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Make a linux network device a router

I am developing an IPv6 network device driver. It should behaviors like a router, i.e. send router advertisement regularly. But now my device is working like a node, send router solicitation. What ...
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314 views

PPTP server with NIC aliases

I have set up a VPN on a VPS Server using PPTP. I have one NIC with two aliases. eth0 eth0:1 eth0:2 The 3 interfaces have public addresses. eth0 is a French IP, eth0:1 is UK, and eth0:2 is ...
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Static IP address shifting to 192.168.1.251

I have a system with a static IP address of 192.168.1.150. I configured /etc/network/interfaces manually (i.e. without using NetworkManager.) It is a web server hosting three sites. I am having ...
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Different domains for multiple VM's on host with one WAN IP

I've got only one WAN IP address bound to KVM host system and multiple VM's with internal IP's, say, 10.0.0.1/28. On the other hand I have multiple domain names bound to host system WAN IP. The ...
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Routing private network to internet via 2 gateways

I have the current set up for an embedded environment: Embedded Target (192.168.0.200) -----> Virtual Machine (VMWare) (2 NIC's - 192.168.0.2 (Target Port) and 192.168.49.69 (NAT Port to host)) ...
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Multiple VPN connetions, routing based on country

I want to set up a couple of VPN connections to two different countries, A and B, on my Ubuntu Server. Then I would like to set up rules based on GeoIP to determine which VPN connection should be used ...
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Static route in Centos 6

Here is my route -n output: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 ...
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use iptables to allow incoming connections to some computer on port XYZ?

This is what I have: iptables -i em1 -A INPUT -j ACCEPT -p tcp --dport 9001 -v. If I want to accept incoming connections on port 9001 at this (127.0.0.1, or on the network 192.168.1.143) address, ...
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Find connections per ip on an OpenWRT router?

How can I list the number of connections per client on the FORWARD chain of an OpenWRT router? I know how to list the number of connections per IP address on the router: netstat -ntu | tail -n +3 | ...
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Limit the max connections per IP using OpenWRT?

Would the following iptables command on an OpenWRT router assure that no one client has more than 50 active connections? $ iptables -I FORWARD -m connlimit --connlimit-above 50 -j REJECT ...
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Routing problem from internal eth1 interface to an external ppp0 interface

I'm trying to connect two LANs using a ppp link. I had a basic network topology diagram but it didn't come out well. This can be seen here. Routing Problem ================ 172.20.0.0/16 ...
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On a router, what decides if a packet should be forwarded or directed into the router itself?

I'm trying to learn how packet routing works on a linux-based router (OpenWRT in my case) a bit better for setting up a few projects/just-learning. Referencing the below chart, I'll break this into ...
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404 views

Connect through different interfaces to the same server (SO_BINDTODEVICE): Destination Host Unreachable

I have 2 interfaces: eth0 and wlan0, each one connected to a different router. Their network specs are these: eth0: ip: 192.168.1.7 Gateway: 192.168.1.1 Submask: 255.255.255.0 wlan0: ...
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How do I apply iptables SNAT to packets bound for localhost (INPUT chain)?

I'm setting up a host that has two routes to the public internet: one via my run-of-the-mill home gateway router, the other via a gateway router on a semi-private network (AMPRNet on 44.0.0.0/8). Most ...
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ICMP gives host an impossible redirect

I am having trouble with forwarding on a system which hosts a few headless VirtualBox VMs. I have not changed anything but the configuration has stopped working. The VMs have IP addresses on their own ...
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Mark packets between machines (client and router)?

Can I mark a packet on the client's OUTPUT chain and add an iproute policy on the router to route them via a specific gateway? This what I tried to do, but it isn't working. My client's mangle table ...
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Routing using second interface

I've got a machine I control running Ubuntu 12.10. I'm on a network that will only allow me to have one device connected. I've also got a USB ethernet adapter. I'd like to create a private network ...
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Allow IP packet forwarding from LAN to modem via router

In short: I'd like to be able to telnet to my modem from my PC via my router. There is a simple home router on 192.168.33.1. It is running OpenWrt. It has the following interfaces defined: br-lan ...
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How to setup DHCPD on two interfaces (Angstrom)

I have an embedded system running Angstrom just fine. This platform has multiple uses, one of which is to act as a home router, so it has wireless and wired network interfaces, which work correctly. ...
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Routing in OpenVPN between a private network and a client

I'm trying to setup OpenVPN between a private network and home clients that connect to it. (The clients don't need to connect to each other). The network topology is a little interesting. There is a ...
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1answer
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Static routes in HP-UX

I need to set static route in HP-UX. I edited /etc/rc.config.d/netconf file and added new entry for my route: ROUTE_DESTINATION[1]="10.105.2.0" ROUTE_MASK[1]="255.255.255.0" ...
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1answer
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Linux ignoring multicast route over loopback

I'm trying to test some multicast code on a single machine. I'm trying to get the packets sent over the loopback device (lo) instead of the default eth1. Googling keeps turning up the incantation ...
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DNS lookup with different Port

I have 2 interface. interface_1 ip address 10.192.0.1 --- interface_2 ip address 192.168.10.2 gw 192.168.10.1 --- default gateway. Not I want to pass my url lookup (keeping 4.2.2.2) with ...
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How to define different routes for global and non-global zone to the same destination?

I have the requirement to separate the management network for global and non global zones in a Solaris 10 server. The global zone has its own management network and all non-global zones share their ...
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1answer
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Packets not forwarded due to second routing table

I've just spent about an hour trying to understand why my docker containers couldn't connect to the internet, in particular couldn't resolve any DNS names. By now I've found a workaround, but I still ...
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NAT box with multiple internal and external interfaces

Similar questions have been asked before but my setup is a little different and the solutions to those questions are not working. A have a CentOS 6 server running iptables with 5 interfaces: eth0: ...
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ip rule not acting on fwmark

I'm trying to use iptables to load balance web traffic over multiple DSL lines by marking the packets and routing based on the mark. I'm working with CentOS 6.6, Kernel 2.6.32-504.16.2.el6.x86_64, ...
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Why is my traceroute hitting the wrong gateway?

What "Should" Happen I want traffic to Google to go through en0 (Mac) and hit gateway A (let's say IP = 123.456.789.000). I have another route setup for en3 and I don't want to mess with that. Tried: ...
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Routing traffic for specific user to specific interface

I have a Linux box with these interfaces: eth0 Link encap:Ethernet HWaddr 14:da:e9:ef:75:7d inet addr:176.9.85.182 Bcast:176.9.85.191 Mask:255.255.255.224 tun0 Link encap:UNSPEC ...
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Making static routes persist after a reboot

I have two VLANs (default vlan and vlan 5 for voip). I have 2 interfaces, one for each VLAN. My route table looks like this right now: Destination Gateway Genmask Flags Metric ...
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Make a request through vpn interface

I want to be able to make request through a specific network interface, like this: ping -I eth0.1 google.be ping -I eth0.2 google.be This example works on my multihomed OpenWRT router. I now want ...
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Default gateway fallback via DHCP configuration

I have a small network, with two routers/Internet connections. I have configured a Raspberry Pi to load balance traffic between these two routers. I would like to have a redundant setup. If one of ...
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Default iterface/routes metric in Linux

When I run ip route on my Linux machine, I see default via xxx.xxx.xxx.xxx dev eno1 metric 202 I wonder, where this 202 metric is configured and what other ip commands use it.
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Assymetric routing problems in LINUX

Assymetric routing problems are driving me crazy! I am trying to build a multi-homed server with 3 NICs. Each NIC is connected to 3 different subnets: eth0: LAN connected, 10.99.72.38; function: ...
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Network connectivity trouble to non-routing multi-homed hosts?

I have two networks: A and B (172.16.2.0/24 and 172.17.2.0/24). A is Ethernet, B is WiFi. An OpenWRT router connects A and B, and most traffic gets passed OK. Default route on router leads to a ...