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

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104
votes
13answers
46k 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 ...
88
votes
12answers
118k 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 ...
60
votes
8answers
9k 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 ...
40
votes
3answers
4k 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
34
votes
5answers
3k 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 ...
31
votes
4answers
6k views

How smart is my network?

There is an argument within my office about how smart/efficient the network we have set up really is. We have a fibre line and a cable line running into a load balancing router, which has a hardware ...
31
votes
5answers
3k 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 ...
29
votes
6answers
31k 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 ...
27
votes
6answers
24k 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 ...
25
votes
2answers
11k 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 ...
22
votes
8answers
54k 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 ...
19
votes
2answers
12k 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 ...
18
votes
5answers
52k 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 ...
16
votes
7answers
37k views

How to direct IP route through specific interface in OS X?

I'm on a mac and trying to route a particular address though a specific gateway on my wifi connection. I'm using: route add -host 54.81.143.201 192.168.15.1 Sometimes this will work, other times ...
15
votes
4answers
18k 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 ...
15
votes
2answers
64k 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 ...
14
votes
2answers
10k 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 ...
14
votes
2answers
317 views

How on earth can this reported hour-long ping time be real?

I recently spent the Easter bank holiday with my parents, who live in a very rural area in the UK. They have a (terrible) ADSL internet connection, which is run over several kilometres of dodgy copper ...
13
votes
4answers
17k 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 ...
13
votes
2answers
6k views

Does the order of entries in the routing table matter?

Does the routing order matter: > route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 123.x.x.151 0.0.0.0 255.255.255.255 UH ...
12
votes
4answers
20k 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 ...
11
votes
5answers
16k 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 ...
11
votes
1answer
42k views

“Network is unreachable” when attempting to ping google, but internal addresses work

I can get to other PCs in my house on the 192 network, but trying to go outside gives me the "network is unreachable" message. p3p1 is up with a good IP Address. Running Fedora 16. What should I ...
11
votes
2answers
15k views

What is the difference between ARP binding and DHCP address reservation?

In my TL-WR1043ND I have these functionalities and both of them pair an IP address to a MAC address. What is the difference? I red that the ARP one is there for security reasons, others say it is for ...
11
votes
2answers
6k views

How does the router know which device to send packets to? [duplicate]

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. ...
11
votes
2answers
3k 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. ...
10
votes
1answer
6k 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?
10
votes
2answers
17k 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 ...
9
votes
3answers
8k 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? ...
9
votes
5answers
17k 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, ...
9
votes
2answers
45k 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 ...
9
votes
3answers
10k 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 ...
9
votes
5answers
52k views

Rerouting local LAN and Internet traffic when in VPN

I'm connecting to a VPN which doesn't allow split tunneling and basically reroutes my Internet traffic through, which is slow. Additionally and more importantly, this also effectively removes my ...
9
votes
1answer
11k views

Route all trafic for specific ip over specific network interface

I have a linux server that needs to get some routing. I'm fairly new at this and i don't find any clear source on google. The setup should be simple: All traffic to a server on ip 192.168.72.20 ...
9
votes
3answers
7k 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 ...
9
votes
1answer
295 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 ...
8
votes
2answers
12k views

How to map an IP adress to localhost?

I want to map the IP address 192.168.1.222 to 127.0.0.1 so that if I use 192.168.1.222 in the web browser or ping command I get the response (and that from my 127.0.0.1). Is this possible via ...
8
votes
4answers
39k 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 ...
8
votes
4answers
22k 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 ...
8
votes
3answers
5k views

Why is tracert showing a private IP address right after my router, even though it has a public IP?

Here is a log of tracert superuser.com from my computer: Tracing route to superuser.com [198.252.206.16] over a maximum of 30 hops: 1 2 ms 2 ms 2 ms 192.168.1.1 2 11 ms 17 ...
8
votes
2answers
10k 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 ...
8
votes
1answer
13k views

On Windows, how to determine route for IP destination?

How can I determine the IP route taken for a specific IP destination (without looking at "route print" and figuring it out manually)? In OS X there's route get 1.2.34 and in Linux there's /sbin/ip ...
8
votes
1answer
7k views

Understanding Windows Routing Tables and Default Gateways

long-time reader, first-time poster! First, let me thank you all for reading this post, and for having such great answers to everyone's questions. I think this is the only time I've had to post ...
8
votes
1answer
298 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
490 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
2answers
51k views

“Connection refused” vs “No route to host”

I have an Apache server running on a server: [root@te-srv2 ~]# ps -ecf|grep httpd root 698 32047 TS 19 10:45 pts/24 00:00:00 grep httpd root 32081 1 TS 19 10:16 ? 00:00:00 ...
7
votes
5answers
3k 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
3answers
3k views

Is there a dual-WAN router that can route based on protocol?

I've got two internet connections at home: DSL and satellite. The DSL connection has bad bandwidth (1.5 Mbps) but very low latency; the satellite connection is the opposite (good bandwidth, terrible ...
7
votes
2answers
23k views

How can I setup a win 7 PC as a router?

I have an industrial PC with 4 Ethernet port, I would like to use this PC as a router on windows 7. Before we used Ubuntu so there is an open source solutiosn, but unfortunately the UPS power supply ...
7
votes
3answers
6k 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 ...