The IP (internet protocol) is a protocol for transmitting data over packets ("datagrams"). It is the primary protocol of the Internet. "IP" may also refer to an IP address, the numerical address assigned to an IP-capable device.

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Transatlantic ping faster than sending a pixel to the screen?

John Carmack tweeted, I can send an IP packet to Europe faster than I can send a pixel to the screen. How f’d up is that? And if this weren’t John Carmack, I’d file it under “the interwebs being ...
300
votes
4answers
38k views

Why does pinging 192.168.072 (only 2 dots) return a response from 192.168.0.58?

I mistakenly missed the dot off of an IP address and typed in 192.168.072. To my surprise I connected to a machine at 192.168.0.58 If I ping 192.168.072 I get responses from 192.168.0.58. Why is ...
109
votes
7answers
5k views

Why can't I email myself at: MyEmail@74.125.235.55?

I opened cmd and typed ping gmail.com. It shows me: C:\Windows\system32>ping gmail.com Pinging gmail.com [74.125.235.55] with 32 bytes of data: Reply from 74.125.235.55: bytes=32 time=6ms TTL=56 ...
89
votes
13answers
9k views

Must TCP use IP?

I have always heard that TCP is short for TCP/IP and they mean the same thing. However, is it not possible for TCP to be built on top of another protocol besides IP?
89
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 ...
71
votes
9answers
11k views

Can you grab any IP address on the Internet?

On a personal network (LAN) one can simply grab an IP address. If you choose the same IP address as an existing client, you get problems. There are companies like IANA and ICANN that are in charge of ...
62
votes
5answers
116k views

How can I list all IPs in the connected network, through Terminal preferably?

Using Ubuntu 10.10, I was wondering if there was a command line command that can list all the IPs of devices connected to the network? I would use this for example, to list all the computers ...
57
votes
6answers
23k views

Why is localhost IP 127.0.0.1?

I wondered what is the origin of the decision to make localhost's IP address 127.0.0.1. What is the "meaning" of 127? what is the "meaning" of 0.0.1?
51
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 ...
35
votes
5answers
2k views

What keeps you from changing your public IP address and wreaking havok?

An interesting question was asked of me and I did not know what to answer. So I'll ask here. Let's say I subscribed to an ISP and I'm using cable internet access. The ISP gives me a public IP address ...
30
votes
7answers
6k views

Do two computers connected on the same Wi-Fi have the same IP address?

Do two computers connected on the same Wi-Fi have the same IP address (for example, my dad's computer and my computer, at home)? If so, how does the outside world distinguishes one computer with the ...
24
votes
8answers
26k views

How can I get my public IP address from the command line, if I am behind a router?

Is there a way for me to get my public (WAN) IP address on the command line? I am behind a router (LAN network), with a dynamic IP address assigned by my ISP. I have seen solutions using an external ...
19
votes
8answers
13k views

Why do we need subnet mask?

Since a IPv4 address already gives the information of the network and and host, why do we still need a subnet mask? The 1st Octet already specify the network class (1-127: A, 128-191: B, 192-223: C ...
19
votes
2answers
5k views

ip versus ifconfig

After reading this answer, I began my quest for the difference between ip and ifconfig for *nix systems. I soon learned that ip had "more" features than ifconfig, but what's the real difference? Is ...
18
votes
6answers
12k views

How can I own an IP address?

How can I own an IP address like I do with domains? I have done some research and it seems that you can't buy a single IP, but rather you have to purchase a range of IP addresses. Update : Important ...
16
votes
5answers
7k views

Ethernet vs TCP vs IP?

What is the difference between Ethernet, TCP, and IP in simple (simple abstract) terms? Please do not copy from Wikipedia...
16
votes
5answers
2k views

What is the actual IP address of my computer

I am testing out to see whats my IP address but depending on which website I used , I get different IP address . I am using a router If i use this , My IP address is If i use this , My IP address ...
14
votes
7answers
10k views

Is it possible for many domain names to share one IP address?

Is it possible for many domain names to share one IP address? For example, www.xjtl.com, www.fmie.com, sdmfl.com, etc. Hundreds of domain names share just one IP – when you do a DNS query for each of ...
14
votes
11answers
27k views

Windows command that returns external IP

Is there a command by which I can find my external IP of my router or my NAT\DSL Router, etc., eliminating the need to visit whatsmyip.net or similar.
12
votes
8answers
3k views

Is it possible to find a printer's physical location in a building by its IP adress?

I am in a school with probably 200+ computers and I did an IP scan among a certain range and found three or four printers. I was wondering if it would be possible to find these printers in the school, ...
12
votes
6answers
44k views

Find an unknown static IP + subnet mask of device?

I have a device set with a static IP and subnet mask. I do not know the IP or subnet mask. How can I find the devices IP and subnet mask? It is a piece of hardware, not a PC. It will not take an IP ...
11
votes
2answers
1k views

Why am I seeing multiple different IP addresses reported as my public IP? [duplicate]

Could anyone explain why these sites are showing me as having different public IP addresses? www.whatismyip.com - 46.19.227.251 as my IP showmyipaddress.com - 46.19.227.253 as my IP ...
11
votes
4answers
9k views

How to make ssh tunnel open to public?

Well refering back to this question i am running the command ssh -R 8080:localhost:80 -N root@website.com on mac. Yet the port that is being tunneled is not working publicly. I am running such a ...
10
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18answers
8k views

Can the Internet work without DNS?

If we have an IP-based system of identifying nodes on the Internet why is there a need for DNS?
10
votes
3answers
4k views

How do routers assign IP addresses?

How does a router assign an IP address? Is this random or is there a set method? It seems that the same device – regardless of the time it was connected – seems to get the same IP assigned. Does the ...
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
5answers
54k views

How to tell what MTU is being used in Windows XP

I'm suffering from a really weird problem where I randomly get "The connection to the server was reset" errors when trying to access web pages (HTTP error 12031 according to the Windows network ...
9
votes
8answers
31k views

How to get my external IP address (over NAT) from the Windows command-line?

The Windows "ipconfig" command can only show me the parameters from the Ethernet interfaces from my machine (even with the ipconfig /all argument). It can show detailed information about the ...
9
votes
4answers
3k views

How is a subdomain passed to the webserver?

I know that dns resolves an address like example.com to an IP address like 11.22.33.44, but I'm a little confused about how subdomains are resolved, so that when you type http://subdomain.example.com, ...
9
votes
3answers
7k views

What is the maximum number of IPs that can be assigned to a given computer?

I really need to know this for a linux server, but since it also applies to client OSes, I figured the question should be posed here instead of server fault.
9
votes
3answers
25k views

What's a loopback-address? I.e. 127.0.0.1

What is a loop-back address? 127.0.0.1 is a loop-back address, but what does this even mean? Please be very descriptive and give an example, as I'm having a hard-time understanding this. Thank You
9
votes
5answers
10k views

Unable to ping local machines by name in Windows 7

I'm having a strange (and persistent!) problem with pinging local machines on my network by name. I believe my machine (Windows 7 64-bit) is the only one having this issue. This is over a wireless ...
9
votes
4answers
799 views

Can I rely on my own DNS server in case of a global DNS blackout?

On March 31st 2012, Anonymous plan to take down the 13 root DNS servers that power the Internet: http://pastebin.com/NKbnh8q8 ... and I don't want to even notice if it actually happens. Assuming ...
9
votes
5answers
5k views

Why can a network address not be a valid host address?

So... I have studied for CCNA and such and been working with IP networking at the least the past 8 years or so. I have always seen and been told that the network address for a subnet is not a valid ...
8
votes
2answers
3k views

Services that just return your public IP as text

I'm writing a script that does dynamic DNS updates for me, but my server is behind a router, and so I need to use a web service to determine my public IP. So far I've found this one which returns ...
8
votes
2answers
922 views

Cannot access pear.php.net from OSX Lion

I am stumped by this issue. I have 2 separate Macs that cannot access pear.php.net at all by name or IP. Here are the symptoms and steps that I took to try to resolve/narrow down this issue. $ ping ...
8
votes
2answers
7k views

How does bridged networking work in Virtualbox?

How does bridged networking work? I have looked through the VirtualBox manuals but nothing extremely technical came up (It was just a generic gloss over of the topic). How does it assign a ...
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
2answers
27k views

How do I setup a virtualbox server with a static ip?

I'm trying to get a Virtualbox instance running with a very specific networking setup. Here's what I have right now: I have a laptop running Ubuntu, hosting a Debian Virtualbox. My loptop regularly ...
7
votes
2answers
532 views

What do the various IP addresses mean?

When I visit a website (e.g. whatismyip.com) it states that my IP address is 13.151.xxx.xxx. However, when I run ipconfig, my IP address is 192.168.0.xx for IPv4 and my DNS adress is 202.xx.xxx.xx. ...
7
votes
2answers
23k views

How to get the real IP address of someone using a proxy?

I was researching digital goods and security when I stumbled upon this company. One of the services they provide is "Real IP". They claim to be able to get the real IP address of users even when ...
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
2answers
9k views

How does circumventing IP restrictions through DNS work in the case of hulu.com?

I just heard from an australian guy that it is possible to watch hulu.com from Australia (which is actually restricted by country IP checks) by using certain DNS servers. Now I was wondering, how ...
7
votes
1answer
431 views

* * * in traceroute

If I traceroute to my server via a bunch of different methods, the external ip seems to not work. However the server is online and accessible by this ip. Localhost: michaelxu@michaelxu-server:~$ ...
7
votes
5answers
949 views

Is it possible to get your router's external ip address without using a website?

I was wondering if there was a way to find out your router's ip address without using a website like www.whatismyip.com. I searched around, and I am beginning to think it is impossible. If that is ...
6
votes
3answers
4k views

how to use two internet connection in one pc at the same time?

I need to use two internet connection at same time. Both the connection will be broadband connection using two LAN. Say, one of the connection's assigned IP is xxx.xxx.xxx.xxx and another is ...
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
2answers
1k views

If you visit a website they will know your IP address. But what about when you change broadband connection?

If you visited a website, of course they will know your IP address, right? But what about when you change your broadband connection? Will they still know that it is still from the same source or ...
6
votes
2answers
4k views

What is the “Alternate Configuration” tab in TCP/IP settings

As I know there is two choice for configuring a computer IP address in the network. Assigning a Static IP or obtaining a dynamic IP from a DHCP server. But what is the Alternate Configuration in ...
6
votes
1answer
407 views

Is computer name a hostname that I can point it to an IP?

On my Windows7, when I get into the properties of My Computer, I can see that my computer name is compname123. It seems that when I ping or connect (say remote access) to this computer from another ...