Questions about using a router/networking, e.g. port forwarding, VPNs

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88
votes
13answers
12k views

What is the exact use of a MAC address?

I understand that IP addresses are hierarchical, so that routers throughout the internet know which direction to forward a packet. With MAC addresses, there is no hierarchy, and thus packet forwarding ...
56
votes
11answers
58k views

How can I make the Windows VPN route selective traffic (by destination network)?

I want to use a Windows VPN but only for a particular network, so that it doesn't take over my entire network connection. e.g., Instead of the VPN becoming the default route, make it only the route ...
50
votes
7answers
6k views

IP address that is the equivalent of /dev/null

Is there an IP address that would result in any packet sent to be ignored (blackholed)? I know I can always set up a router with an IP address and then just have it ignore all packets sent to it, but ...
37
votes
3answers
3k views

What's 24 in “192.168.15.0/24”?

What's the meaning of /24 in the following command? route add -net 192.168.15.0/24 192.168.8.10
33
votes
5answers
2k views

What stops an internet router from sniffing my traffic?

Packets travel through internetworks, and take many routes through internet routers. On each route that forwards traffic to another until reaching the ultimate destination, what stops them from ...
26
votes
5answers
2k views

How do I tell Windows to use 802.11 in preference to 3G?

I have a Samsung NC-10 netbook which I take to work every day. Most of the time I use it just on the train/bus, but I also use it at work and home. It has a built-in 3G card which I want to use when ...
25
votes
5answers
16k views

Does DD-WRT QoS actually work?

There have been various reports of DD-WRT QoS not working (here, here and elsewhere). The DD-WRT QoS Documentation mentions some checks would indicate whether the proper priorities are being applied ...
18
votes
5answers
16k views

How to force split tunnel routing on Mac to a Cisco VPN

Any one know how to hack the routing table (on a mac) to defeat the forcing of VPN routing for every thing over a cisco VPN? pretty much what I want to do is have only 10.121.* and 10.122.* addresses ...
16
votes
2answers
5k views

Does All LAN Traffic Travel Through A Router

I have a very simple question: if I have a router (DHCP enabled - leasing IP addresses between 192.168.0.2 and 192.168.0.254) with a switch plugged in, and I plug two computers into the switch, will ...
15
votes
5answers
24k views

Access internal IP using public IP

I have a DSL modem with a public IP address (201.206.x.x), and I have a web server in my internal network (192.168.0.50). I set up the modem to forward requests to port 80 to my web server, so, if I ...
13
votes
4answers
34k views

How to tell Windows 7 to ignore a default gateway

I currently have 2 network cards in my PC -- one connected to an internal network on a router with a disconnected WAN port (10.x.x.x), and one connected to the internet through a consumer router ...
13
votes
3answers
9k views

How can I ping via an alternate gateway?

Our network has two modems, each one hidden behind a router. The primary router is on 10.1.1.1, the backup router is on 10.1.1.2, and are both configured to the 10.1.1.0/24 subnet. Both routers have ...
12
votes
4answers
13k views

How do I setup Ubuntu/Linux's Network manager to selectively route network traffic through the VPN?

I'm using Ubuntu 9.04 and I just noticed that ALL of my network traffic is being routed through my VPN. I would like the VPN to route only the traffic hitting servers on the VPN and then connect ...
12
votes
2answers
3k views

How do you get loopback addresses other than 127.0.0.1 to work on OS X

According to everything I read, the entire 127.x.x.x subnet should loopback. However, on my Mac, I can only ping 127.0.0.1 I know I've done this before (though possibly on another OS) and has come ...
10
votes
3answers
38k views

How to route only specific subnet (source ip) to a particular interface?

How to route only specific subnet (source ip) to a particular interface? OS: Linux I know I can do easily by destination IP by using something like route add 1.2.3.4/24 dev eth4 but I do not ...
9
votes
4answers
14k views

How do I bridge two wired DD-WRT routers?

I have one DD-WRT router (herein: 1st) connected to the Internet, working perfectly, with client PCs assigned static IP addresses. Now I want to add another static client (herein: 2nd), but this time ...
8
votes
4answers
9k views

Prevent VPN from changing DNS on Windows 7 / 8 developer preview

I have a customer that uses a VPN connection, however it automatically configures my DNS settings to a non-existent DNS server, meaning every DNS resolution times out until the alternative is tried, ...
8
votes
2answers
15k views

Virtualbox: How to access web server on guest OS from the host OS?

After a lot of RTFM'ing and reading forums, I am still having problems and need some advice. I use Virtualbox on Ubuntu and installed a Centos server as a guest. My problem is that I cannot access the ...
8
votes
2answers
2k views

How do I make certain web addresses use a specific network adapter on Mac OS X?

I have two Internet connections at work, my wired Ethernet connection (which is heavily filtered behind a firewall, can't connect to Apple Updates, etc.) and a wireless connection that is unfiltered. ...
8
votes
1answer
103 views

Hooking Linux machine to secondary router/ISP: how to setup routing correctly?

Abstract: I have (I presume routing) issues when adding a secondary ISP to my existing network setup: incoming traffic through Router1 is not answered, but local traffic and incoming through Router0 ...
8
votes
2answers
360 views

Always use one slow connection in preference of a “faster” one

In Windows, there's this automatic metric thing where the metric is selected according to the declared speed of the link. I now have a gigabit LAN routed to a 2Mbps DSL service and a HSDPA mobile ...
7
votes
3answers
4k views

What's the difference between 127.0.0.1 and 127.0.0.0

I know that both are loopback IPs, but they have another ip mask. What's the difference between them? Can they be used interchangeably? ...
7
votes
5answers
2k views

My university tells me I can't use a router in my dorm. Is there any way they can tell?

We're behind some kind of Cisco routers, and have to connect via the Cisco NAC Agent. The tech support here at my university tell me that if I connect a router "the whole building will lose internet ...
7
votes
2answers
5k views

Stop VPN being used on internet traffic on Win 7 [duplicate]

Possible Duplicate: How can I make the Windows VPN route selective traffic (by destination network)? How To Use Local Internet Connection To Access Internet While Still Connected with VPN ...
7
votes
2answers
8k views

What is “Disable class based route addition” good for?

In the advanced TCP/IP settings of a VPN connection, i found a checkbox labeled with "Disable class based route addition". The checkbox is only enabled as long as "Use default gateway on remote ...
7
votes
1answer
2k views

iptables vs route

What's the difference between these two tools? Can anybody tell me what the main workflow of networking behind Linux (in relation to IPv4 packet filtering, NAT and IP routing table) is?
7
votes
3answers
3k views

Disable CISCO VPN client routing for selected subnet on Mac OS X

I'm using a Mac laptop and when I am connected to the CISCO VPN, all traffic is routed through the tunnel. However I need to run a VM (VirtualBox with Ubuntu as guest) for certain services. VM is ...
7
votes
3answers
3k views

How does the router know which device to send packets to?

my question does not concern how it moves through the internet, but how it moves through the router to a certain device. All devices connected to a router in a home network have the same external IP. ...
7
votes
4answers
13k views

Routing all Traffic through OpenVPN Tunnel

I have installed OpenVPN server on Archlinux and am now using OpenVPN GUI on Windows 7, I can talk to other computers connected through the VPN but I have not yet figured out how to route all traffic ...
6
votes
5answers
7k views

How do IP answer packets reach their destination inside of a private LAN?

This is a little theory question that has been confusing me for a pretty long time. Basically, if we are inside of a private LAN, and we want incoming packets to reach, for example, an HTTP server ...
6
votes
4answers
23k views

When a PC has both a wired and a wireless connection, how is information transferred?

My PC has two connections (wireless and wired) simultaneously. Both of them have an internet connection. In this situation, how does it connect to the internet? How do my LAN and WLAN interfaces know ...
6
votes
2answers
18k views

Using “route add” to tell my computer to use a direct ethernet connection instead of wifi?

2 PCs are involved. Both are connected to the internet via Wifi on the same router. I can ping to/from each other and share folders flawlessly, but I'd like to be able to set a direct Ethernet link ...
6
votes
1answer
255 views

Why is the windows routing table huge?

This is a bit of a pointed question, but begs being asked: Why is the windows routing table abnormally large? Go to a command prompt, and type "route print". You'll probably get >3 entries, even for ...
6
votes
1answer
6k views

Routing traffic to specific web sites through Ethernet, rest via wifi on Mac OS X 10.6?

I have two separate Internet connections connected to a Mac and I'd like one of them (via Ethernet en0 gateway) to serve for just backing up to an remote online storage, and the other one (via Airport ...
6
votes
4answers
7k views

How to set up application-specific routing table on Windows?

Suppose network interface 1 (net1) and 2 (net2) are both connected to the Internet. I want application 1 (app1) to use net1, and application 2 (app2) to use net2. How can it be done under Windows? If ...
6
votes
1answer
147 views

What is a good way to get back to the command prompt discarding STDOUT and STDERR

I often launch applications from the cli via e.g. command & to immediately get back to the prompt back. The downside of this is, that I still get STDOUT and STDERR. So I use command &> ...
6
votes
1answer
910 views

How does Google bypass IP routing?

At the Google Public DNS Performance Benefits page, they claim In Google Public DNS, we have implemented several approaches to speeding up DNS lookup times. Some of these approaches are fairly ...
6
votes
2answers
8k views

Setup routing and iptables for new VPN connection to redirect **only** ports 80 and 443

I have a new VPN connection (using openvpn) to allow me to route around some ISP restrictions. Whilst it is working fine, it is taking all the traffic over the vpn. This is causing me issues for ...
6
votes
3answers
3k views

Home network with two isolated separate subnets, running on cablemodem/router and WRT-router

I have a new connection with a nice new router/cable-modem. I'd like to setup it up optimally and needs some pointers. I am a complete n00b when it comes to routing. I want to end up with two ...
6
votes
3answers
3k views

SSH server can't be connected to when VPN is turned on

I recently found that when my workstation connects through a VPN connection then its SSH server can't be connected to from a remote site. I am sure it's a routing problem because the the VPN client ...
6
votes
1answer
1k views

How do I troubleshoot distant Internet routing problems?

(This may be better answered on serverfault, but it's not technically about a server, so suggestions welcome...) We just moved offices at work. We're in Cambridge, MA, and have a Comcast ...
6
votes
2answers
5k views

How do I join two subnets with two DD-WRT routers?

I have two separate DD-WRT routers which I would like to bridge together so that computers connected to each are on the same subnet (so that multicast can work between them for UPNP/DNLA media ...
6
votes
2answers
30k views

How to set permanent route in Ubuntu 10.10?

I'm trying to configure my wireless network to use gateway 10.0.1.252 when accessing IP addresses that start with 10.0.0. I followed a few explanations on how to do it with the interfaces file but ...
6
votes
0answers
188 views

Internet Sharing on Lion breaks my routing table

When in the office, I'm connected to a 192.168.1.0/24 network. When Internet Sharing is off, when I run netstat -nr the first entry shows default 192.168.1.254 UGSc 10 ...
5
votes
1answer
537 views

Exactly how many valid IPv4 addresses are there?

Seemingly simple question, with enough edge and corner cases that I don't trust my ability to calculate it. What is the exact number of valid IPv4 addresses that could potentially be used as ...
5
votes
2answers
38k views

Windows 7: how can I add an IP range in the “route” command?

I'm using two network connections, and I tried using the "route" command so that when I access a specific internal IP on my LAN, it would use connection 1, anything else would go normally through ...
5
votes
3answers
686 views

Multiple home routers

Suppose I have the following configuration: Router A: WAN port connected to the Internet, LAN = 192.168.1.0/24 Computer A: Connected to router A as 192.168.1.101 Router B: WAN port connected to ...
5
votes
1answer
7k views

Problem with persistent routes and VPN connection in Windows 7

My home PC has a VPN connection to my office. The office network is firewalled, with a secure zone on 192.168.0.* and a DMZ on 10.0.0.* From outside, www.mycompany.com routes to a public IP - say ...
5
votes
3answers
3k views

prevent connector routing when elements placed on top of them in MS Visio 2007

Is there any chance to prevent MS Visio (preferably 2010) connectors from routing when a text block is placed on top of it? I want to achieve the effect as if the text block is on the upper layer, ...
5
votes
1answer
48 views

How do I route requests for an entire subnet over a VPN connection on Ubuntu?

I have an Ubuntu machine connected to a VPN, with the IP address 172.16.1.250. I want to tunnel all the requests for 172.16.1.* through the VPN, but nothing else. If I try to use sudo route -net add ...