the process by which data packets on communication networks are forwarded into the direction of their ultimate destination by routers.

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44
votes
2answers
149k views

Can I have multiple DHCP servers on one network?

This is a Canonical Question about Redundant DHCP Servers. Is it possible to have more than one DHCP server on the same LAN? What are the implications of doing this? What happens if there is ...
54
votes
8answers
48k views

What is “anycast” and how is it helpful?

I'd never heard of anycast until a few seconds ago when I read this SF post. The wikipedia entry on it is quite formal and doesn't really evoke a mental picture of how it would be used. Can someone ...
14
votes
4answers
41k views

iptables - Target to route packet to specific interface?

My home server has two main interfaces, eth1 (a standard internet connection) and tun0 (an OpenVPN tunnel). I'd like to use iptables to force all packets generated by a local process owned by UID ...
16
votes
5answers
107k views

How to route different traffic thru different network interfaces (in Windows)

I've searched for details on how to do this but I've been unsuccessful - I wondered if someone could offer up some advice. So, let's say I have 2 network cards (LAN and 3G in my instance), both ...
8
votes
4answers
3k views

Multi-WAN bonding across different media

I've recently been thinking again about a product that Viprinet provide, basically they've got a pair of routers, one that lives in a datacentre, Their VPN Multichannel Hub and the on-site hardware, ...
10
votes
1answer
61k views

Two network interfaces and two IP addresses on the same subnet in Linux

I recently ran into a situation where I needed two IP addresses on the same subnet assigned to one Linux host so that we could run two SSL/TLS sites. My first approach was to use IP aliasing, e.g. ...
8
votes
4answers
14k views

second ip address on the same interface but on a different subnet

Is it possible in CentOS 5.7 64bit to have a second IP address on one interface (eg. eth0) - alias interface configuration - in a different subnet? Here is the original config for eth0 more ...
4
votes
2answers
743 views

IPv6: differences between “routed prefix” and “link prefix”?

What are the exact differences between "routed prefix" and "link prefix" for IPv6?How do these differences in a wireshark-Trace? (if you observe a Host with an assigned "routed prefix" or a Host with ...
5
votes
2answers
2k views

Policy based routing

I found very good article on load balancing at http://www.diegolima.org/wordpress/?p=36.. I could not implement it though as my requirement is slightly different from pure load balancing. We have two ...
4
votes
2answers
2k views

IP Routing - how does it work again? [closed]

Can someone explain how IP routing works to me? E.g. if I ping 123.123.123.123, how does each router know which way to go as shown in a traceroute dump.
58
votes
3answers
96k views

What is the difference between unicast, anycast, broadcast and multicast traffic?

I have never had the privilege of working in an environment that required complicated routing or if it did require it, it was handled upstream of me. I've always used very simple static routing ...
30
votes
3answers
20k views

Tuning Linux IP routing parameters — secret_interval and tcp_mem

We had a little failover problem with one of our HAProxy VMs today. When we dug into it, we found this: Jan 26 07:41:45 haproxy2 kernel: [226818.070059] __ratelimit: 10 callbacks suppressed Jan 26 ...
12
votes
3answers
22k views

Public static ip for vagrant box

I have server (Debian Squeeze) with 1 ethernet card and 2 public static IPs (188.120.245.4 and 188.120.244.5). What I want: Setup virtual box (Ubuntu) with access via static IP (188.120.244.5). ...
8
votes
1answer
14k views

Difference beetween DNAT and REDIRECT in IPTABLES

Okay, it may be because I am dense or maybe just not finding the right source, but I can't understand why one of these IPTABLES setups would be better than the other. Here is my setup: I have a box ...
5
votes
2answers
6k views

Can't ping multihomed Linux machine on non-default interface

I have a multihomed Ubuntu server with a set of interfaces that includes: eth2: 10.10.0.131/24 eth3: 10.20.0.2/24 The default interface is eth2, with a gateway of 10.10.0.1. Here's what the routing ...
2
votes
2answers
15k views

Routing decision when there are two default gateways on windows

My windows machine has two network cards, both have default gateways. How does windows determine which gateway should it access when sending a packet to a remote endpoint? More precisely, here's my ...
5
votes
2answers
3k views

Routing selection: specificity vs metric

I understand that Linux chooses the most specific route to the destination when it does routing selection. But what about a route's metric? Does it have a higher priority than route's specificity? A ...
3
votes
1answer
3k views

OS X 10.8: redirecting locally initiated ssh connections to localhost:22

I need to hack the OS X pf to redirect all ssh connections from an user to this machine. I want, when doing $ ssh google.com to get the same results as with $ ssh localhost ie a connection to ...
2
votes
1answer
5k views

How to configure routing between Azure virtual networks?

I'm designing an Azure environment which will contain multiple virtual networks, and a requirement is for all networks to be connected; a VM in any network should be able to talk to another VM in any ...
1
vote
1answer
1k views

Is there any way to filter packets (eg. by iptables) after routing is complete?

I want to drop certain packet destined to an ip_address AFTER it has reached the POSTROUTING chain. However, for iptables, the "nat" table cannot be used for filtering so the following doesn't work: ...
5
votes
4answers
2k views

Prevent SSH connection lost after logging into VPN on server machine

I encountered an issue that I can't deal with. When I'm logged onto an VPS over SSH and try to estabilish VPN connection on that VPS, the SSH connection between VPS and my machine get lost. I assume ...
3
votes
1answer
47k views

Setting a static route for a specific network adapter with two network adapters

I have a virtual windows server 2008 r2 with 2 virtual network adapters, one is part of a domain and the other isn't. When I ping to a specific PC that is part of the domain it connects to it through ...
2
votes
2answers
5k views

iptables packet forwarding to one of two gateways depending on origin

Given the following installation: old router 192.168.1.1 with NAT forward of tcp port 80 to 192.168.1.10:80 new router 192.168.1.2 with NAT forward of tcp port 80 to 192.168.1.10:80 web ...
2
votes
2answers
11k views

How can i forward the http and ssh port to my internal server using iptables

I do not have the router so i make the Linux system into router having centos 6.4 for forwarding the Public network traffic to my local LAN.It has the two NIC card. one for public ip (eth1) and ...
2
votes
1answer
6k views

OpenVPN not redirecting all traffic through VPN

I have just finished setting up my VPN, and google shows my IP to be that of my VPN, so this works fine. However, when I log in through SSH to the VPN server, it shows my last login to be that of my ...
2
votes
2answers
2k views

Change source address based on destination IP

We have several "router" machines that gather a lot of external IP addresses on the same host and redirect, NAT or proxy the traffic to the internal network. They also act as routers for the machines ...
2
votes
1answer
13k views

OpenVPN server cannot ping clients

I have OpenVPN set up on a Debian server. Clients can connect, and clients can ping and access resources (Samba shares and intranet) on the server. However, the server cannot ping the client - it ...
2
votes
1answer
1k views

How to configure Routing, VPN and masquerading in Windows?

I need to link a branch office to a new subnet. I'm doing something wrong. I try to be more specific: I have this object virtually connected as follows: GW_U ---- S-OpenVPN ----- OpenVPN-C ----- ...
2
votes
3answers
498 views

Linux router with 4 NICs not working

I'm setting up a Linux based router, with 4 NICs, and I can't seem to convince it to work, despite following steps suggested on various web sites. Each interface is on a separate subnet as follows: ...
2
votes
5answers
7k views

Route return traffic to correct gateway depending on service

On my office network I have two internet connections and one CentOS server running a website (HTTPS on port 443). The website should be publicly accessible through the public IP of the first internet ...
2
votes
5answers
3k views

Link aggregation with DSL and Ethernet, and different ISP's?

We're a webdev company that has outgrown its ADSL bandwidth. It's currently 4/1 Mbit/s and due to distance we can't simply get faster DSL, whether ADSL or SDSL. Stacking multiple DSL connections is ...
0
votes
1answer
630 views

Configure routes in OpenVPN

I am trying to figure out how to setup routing on OpenVPN. I have successful connection between client (OS X Snow Leopard) and server (OS X Leopard Server), and each can ping the other. However, I am ...
7
votes
2answers
2k views

Routing via Cisco ASA is changing TCP sequence/ACK numbers

Our network has a dedicated VPN appliance that sits inside the office network. We have a Cisco ASA with a static route that routes the VPN subnets to the VPN appliance. So a typical request from the ...
5
votes
10answers
14k views

Forward port to another Ip/port

I recently found out that my ISP disables port 135. I have a server and personal computer behind my router. A friend and I are working on a programming project and are running into some sql issues ...
4
votes
2answers
582 views

EIGRP neighbors flapping

I have a EIGRP topology set up in GNS3. It looks like this: The neighbor relationship between R7 and R8 is constantly flapping and I cannot figure out why. Hello timers and time delays are all set ...
2
votes
2answers
1k views

BGP Multihomed/Multi-location best practice

We're in the process of designing a new iteration of our network where we improve resilliency by adding a second datacentre. We'll be adding a second datacentre, with an identical configuration of ...
1
vote
1answer
511 views

why port forwarding is not working in this setup?

I'm trying to setup a docker virtualization environment. This is a follow up of this question. I have a virtual eth0:0 interface, and I would like to forward it using iptables. The public, main IP ...
1
vote
1answer
462 views

Why did my new iptables rules screw up outbound traffic?

I recently set up Tomcat on Port 80 using instructions provided by Werner Puschitz. In essence, I had to execute these two iptables commands: iptables -t nat -I PREROUTING -p tcp --dport 80 -j ...
0
votes
1answer
338 views

Using a CIDR range as a Routed Subnet?

I have a /29 subnet assigned by my ISP, with an SonicWALL office router and a Cisco voice router hooked up to a 'net-rail' of sorts with untagged VLAN switch ports connecting my ISP router's output ...
0
votes
1answer
3k views

Cisco ASA 5505 Voice/Data VLANs not pinging/routing

Hi i am very new to Cisco ASA 5000 series and have two interfaces that i would like to route between, a data network 192.168.69.0/24 and voice 192.168.70.0/24, I have addded both and can ping the ...
0
votes
1answer
252 views

Local server outside: How to access url internal over router?

i have the following problem: i installed a new test-mailserver in our office today and did some port-forwarding on our router to the specific mailserver ports. everything works fine, except the ...
0
votes
3answers
1k views

Policy Routing with Openvpn?

Dear Everyone I am currently using openvpn for normal browsing. However, I have the following services running: a bit torrent client, a web server, IRC and a git server which I would really want it to ...
14
votes
2answers
26k views

Where route to 169.254.0.0 comes from?

Running CentOS 5.4 Why do I have route to 169.254.0.0 although it does not appear in Network > Ethernet Device > Route configuration dialog? Destination Gateway Genmask Flags ...
15
votes
4answers
22k views

How is route automatic metric calculated on Windows 7?

KB299540 explains how Windows XP automatically assign metrics to IP routes: The following table outlines the criteria that is used to assign metrics for routes that are bound to network interfaces ...
8
votes
2answers
8k views

ip address scope parameter

In Linux, the command ip address add [...] has a scope argument. The man page says that the scope is "the scope of the area where this address is valid". Follows the list of legal scopes: global ...
7
votes
5answers
41k views

Ping “replies” from same computer with 'Destination host unreachable' (no route to other computer)

I've got two computers in a LAN behind a wireless router. One has XP with ip 192.168.1.2 This one has W7 with ip 192.168.1.7 If I try to ping the other one from this computer, I get this: ...
0
votes
1answer
8k views

Using DD-WRT to connect to VPN and Forward all traffic of certain devices through VPN

I have been able to setup my dd-wrt router to connect to an openvpn server and route all traffic through the vpn to the internet. This makes it so all traffic comming in from the LAN to the ...
5
votes
3answers
15k views

Routing WIFI and LAN for specific traffic

I have two network devices aboard my macbook pro: WIFI (en1): Used for general traffic. Connects to an ip of 192.168.19.* via DHCP LAN (en0): Used for specific traffic. Connects to an ip of ...
2
votes
2answers
6k views

Permanently adding source policy routing rules

Somebody answered my earlier question by describing how to create a new routing table with source policy routing: echo 13 eth3 >> /etc/iproute2/rt_tables ip route add default via 10.20.0.1 ...
1
vote
2answers
2k 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 ...