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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681
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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 ...
332
votes
4answers
41k 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 ...
116
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 ...
98
votes
13answers
30k 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 ...
95
votes
13answers
10k views

Must TCP use IP?

Is it true that TCP is short for TCP/IP and they mean the same thing? Is it possible for TCP to be built on top of another protocol besides IP?
84
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5answers
185k 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 ...
77
votes
9answers
14k 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 ...
69
votes
8answers
6k views

Are IP addresses with and without leading zeroes the same?

I have a security system and the network setting only allows a three-digit IP address. I can't set it to 192.168.2.100, instead I have to use 192.168.002.100. Are these two IP addresses different? Do ...
65
votes
6answers
29k 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?
56
votes
7answers
8k 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 ...
38
votes
7answers
40k 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 ...
38
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 ...
34
votes
4answers
25k 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 ...
30
votes
9answers
44k 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 ...
27
votes
7answers
27k 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 ...
22
votes
8answers
21k 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 ...
21
votes
7answers
69k 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 ...
20
votes
2answers
6k 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
14answers
50k 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.
17
votes
5answers
11k 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...
17
votes
1answer
2k views

Pinging different IP address than what I entered [duplicate]

Can anyone please explain why CMD pings a different IP address than the one I am searching for?
17
votes
5answers
3k 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 ...
16
votes
7answers
28k 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 ...
15
votes
2answers
54k 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 ...
13
votes
5answers
2k views

Identify an unknown IP in our network

I have a network containing 20 clients. I assigned IP range 10.0.0.1 to 10.0.0.20 to them. When I do an IP scanning I see someone using 10.0.0.131 in VMware. How can I find out which IP is this IP ...
13
votes
4answers
6k views

Services that just return your public IP as text [closed]

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 ...
13
votes
2answers
14k 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 ...
12
votes
8answers
5k 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
5answers
85k 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 ...
12
votes
3answers
39k 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.
12
votes
2answers
37k 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 ...
11
votes
2answers
2k 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
3k views

How do I find out which program and process ID accesses a given IP address in Windows?

Is it possible to catch, which program is accessing a specific IP address? I found my computer is flooding and wish to check addresses one by one. May be it is possible to set up some audit for ...
11
votes
5answers
18k 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 ...
11
votes
4answers
99k views

Setup static IP under Ubuntu 14.04 Trusty

How to setup static IP address under Ubuntu 14.04 Trusty? My setting is not working. What special about Ubuntu 14.04 Trusty is that I found it now using the "source-directory" keyword to source ...
11
votes
7answers
7k 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 ...
10
votes
18answers
11k 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
8answers
47k views

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

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 ...
10
votes
2answers
597 views

Using only AAAA record for a domain?

Can I point a domain to IPv6 only, instead of IPv4 and will it be fully functional? I've searched for a tip on the Internet, but I've found only for using both.
10
votes
3answers
10k 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.
10
votes
3answers
8k 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
5answers
914 views

How to check public IP address availability

I have a few public IP addresses given by the ISP service provider. My question is how to check which IP addresses are already used up and which are still available to use for new servers? Because I ...
10
votes
2answers
11k 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 ...
9
votes
3answers
7k 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
4answers
4k 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
5answers
11k 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 ...
9
votes
2answers
15k views

What is the difference between a subnet mask and a netmask?

Is there any logic in using two different names for determining host ID and net ID? For example, if you type print route in a Command Prompt you get things with netmask, but the IPv4 settings seems ...
9
votes
4answers
37k views

How to find the IP Address of a vm running on VMware (or other methods of using VM)

I am running VMware Workstation on a Linux box. When I power on a centOS (Linux) virtual machine I cannot get mouse or keyboard control of the machine. I suspect that it has something to do with ...
9
votes
4answers
910 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
17k views

Is it possible to host a web server from behind a NAT

My PC is behind a NAT router that has a public IP address. If I want to host a website then I believe I need a domain name which I can purchase from some site which would pledge to resolve all DNS ...