IP - Internet Protocol, the most commonly-used set of rules for dispatching data across a large computer network.

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135
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5answers
192k views

MySQL: Bind to more than one IP address?

Is there a secret way to bind MySQL to more than one IP address? As far as I can see the bind-address parameter in the my.cnf does not support more than one IP and you can't have it more than once.
106
votes
10answers
285k views

What's the command-line utility in Windows to do a reverse DNS look-up?

Is there a built-in command line tool that will do reverse DNS look-ups in Windows? I.e., something like <toolname> w.x.y.z => mycomputername I've tried: nslookup: seems to be forward ...
91
votes
4answers
95k views

What's the difference between ip address 0.0.0.0 and 127.0.0.1?

I do know that 127.0.0.1 ~ 127.255.255.254 are the loopback IP addresses for most modern operating systems and we could use these IP addresses to refer to our own computer. But what's 0.0.0.0? It ...
57
votes
6answers
471k views

How to determine the hostname from an IP address in a Windows network?

My LAN has 50 Windows hosts. At the Windows command line I try ping to get the IP address of a running Windows machine. The question is how to get hostname of a specific IP address in the same ...
43
votes
5answers
4k views

Why is tampering with the TTL of IP dangerous?

I've been reading the iptables man-page (light bedtime reading) and i came across the 'TTL' target, but it warns: Setting or incrementing the TTL field can potentially be very dangerous and ...
42
votes
7answers
30k 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 ...
39
votes
3answers
58k 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 ...
36
votes
12answers
11k views

Why would you use IPv6 internally?

Of course, I realize the need to go to IPv6 out on the open Internet since we are running out of addresses, but I really don't understand why there is any need to use it on an internal network. I have ...
33
votes
5answers
4k views

Is it valid to have part of an IPv4 address set to zero?

I am working on a change in a Java EE application that would authenticate based on the user's IP address using ServletRequest.getRemoteAddr. We store IP address ranges (FROM_IP and TO_IP) in a ...
31
votes
4answers
8k views

Users with Google's IP address. How is it possible?

I have a spanish website and I do not allow people from non-european countries to register and to login. Some time ago I started to receive messages from users who can not login. When I ask for their ...
30
votes
7answers
16k views

How many computers can have the same public IP?

I've got a list of hundreds of page requests from the same IP and I need to know if these could be requests by different computers.
30
votes
5answers
79k views

Why do we ping the IP 4.2.2.2 to test connectivity?

For as long as I can remember, I've always used the IP 4.2.2.2 when testing network connectivity using ping. What is significant about this IP, and when did this practice start?
29
votes
5answers
3k views

Is 0.1.2.3 a valid IP address?

Are IP addresses with all zeroes in the first octet valid? For example, can 0.1.2.0/24 be a valid subnet, with network address 0.1.2.0, broadcast address 0.1.2.255 and an usable address range from ...
29
votes
5answers
10k views

Debugger for Iptables

I'm looking for an easy way to follow a packet through the iptables rules. This is not so much about logging, because I don't want to log all traffic (and I only want to have LOG targets for very few ...
25
votes
13answers
206k views

How to get a list of all IP addresses (and ideally device names) on a LAN?

Our network gave an error that there was an IP address conflict and I'd like to find what all the device IP addresses are. (I've also had need of that before). (update/clarification:I'm looking for a ...
25
votes
6answers
22k views

Is it possible for two hostnames share the same IP address?

Can anyone explain whether it is possible for two hostnames to share the same IP address? And what about if one hostname represents more than one IP address, is that possible too? Why?
24
votes
3answers
22k views

Where does Amazon publish the range of IP addresses used for EC2 instances by region?

How can I keep updated of changes to the range of IP addresses that Amazon will use for EC2 instances. I want to add a range of IPs to my firewall settings to allow access to my 'ground based' mysql ...
20
votes
2answers
2k views

Pinging an IP address responds with different IP

When I try to ping the IP address 10.10.208.57 I have no response since nothing exist in the network with that IP address. However if I try to ping 10.10.208.057 instead another IP address responds: ...
20
votes
3answers
26k views

How do I block specific IPs and IP ranges in IIS7?

I'm trying to block various IP addresses from every site that I have hosted from an server running Windows 2008 and IIS7. I've found various information about how to do this using Deny rules from ...
19
votes
2answers
5k views

What does [::] mean as an ip address? Bracket colon colon bracket

When I run netstat there are some entries such as TCP [::]:8010 computername LISTENING What does that mean? It is impossible to search for...
18
votes
8answers
13k views

What is the network address (x.x.x.0) used for? [duplicate]

It appears to be common practice to not use the first address in a subnet, that is the IP 192.168.0.0/24, or a more exotic example would be 172.20.20.64/29. The ipcalc tool I frequently use follows ...
17
votes
7answers
22k views

Force local IP traffic to an external interface

I have a machine with several interfaces that I can configure as I want, for instance: eth1: 192.168.1.1 eth2: 192.168.2.2 I would like to forward all the traffic sent to one of these local ...
16
votes
9answers
72k views

Any way to find unused IP addresses on my network?

How can I locate unused IP addresses on my network? The DHCP server keeps assigning the same address and I need a different IP address to test my application with. The software would need to run on ...
16
votes
1answer
4k views

Change TeamCity IP address and port number on multi-homed Windows Server 2008 running IIS 7

After two full days of "research" (read: banging my head against my keyboard) and cursing at TeamCity/MSDN/Tomcat documentation as well as phantom IIS bindings, I've come up with an answer to a very ...
15
votes
1answer
684 views

Under what circumstances is TCP-over-TCP performing significantly worse than TCP alone (2014)?

Many admins keep perpetuating - on ServerFault and elsewhere - how bad of an idea TCP-over-TCP is, e.g. in VPNs. That even the slightest packet loss will make one suffer from at least severe ...
14
votes
4answers
2k views

What does my ISP mean when they say they will provide “4 static IPs out of which 2 are usable”? [duplicate]

I am planning to get leased line installed at my office. I have talked to one of the ISPs about static IP. They said I'll get 4 static IPs out of which 2 are usable. What does that mean?
14
votes
4answers
18k views

Can the IP address for an HTTP request be spoofed?

On a website I am building, I plan to log the IP addresses of submissions, just in case it's necessary. I don't mind proxies, but outright spoofing your IP address would defeat the purpose. To ...
14
votes
5answers
79k 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 ...
13
votes
7answers
13k views

Can a single network card have 2 IP addresses?

Are network cards and IP addresses a one-one map?
13
votes
1answer
1k views

Several IPs per server. Why?

Usually providers allow to add additional IP addresses to your server. I don't understand why. I can't imagine any common usecase which needs several IP addresses for one server.
13
votes
3answers
3k views

How are IP addresses actually assigned?

I'm having a hard time understanding how a governing body assigns IP addresses, companies use BGP to advertise those IPs, and how the internet works. Then, where the hell does DNS come in? Can ...
13
votes
4answers
17k 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 ...
12
votes
5answers
2k views

What are the benefits of having an unique IP address?

I just signed up with DreamHost VPS, and their sign-up process offered an unique IP address for an additional ~$4/mo. I know what IP addresses are. Why would this uniqueness matter? Visitors are ...
12
votes
4answers
14k views

How to make Postfix use another IP address?

I'm using the Postfix mail server and I have 6 IPs available. I'd like to use another IP for the Postfix mail server for sending mail than the web server uses. How can I do this? My postfix version ...
12
votes
4answers
15k views

Block range of IP Addresses

I am getting bombarded with attempted hacks from China all with similar IPs. How would I block the IP range with something like 116.10.191.* etc. I am running Ubuntu Server 13.10. The current line ...
12
votes
6answers
22k views

Why was my ping answered by a different IP address than the one pinged?

While trying to setup a MSSQL clustering solution, I am running into a problem that is outside of my expertise that is related to networking. I was trying to find a free IP to used for my node. I ...
12
votes
2answers
3k views

Machine always responds to 192.168.1.2 IP address, which is not set on the machine

UPDATE BELOW: UPDATE 2 BELOW: FINAL Solution I have a brand new HP EliteBook notebook 8560p running Windows 7 64bit. I plug it into a small Dlink di-604 router, it is currently configured with DHCP ...
11
votes
2answers
1k views

Multiple IP addresses per NIC

How can I have multiple IP addresses assigned to a single NIC? I remember doing this on Unix way back when. Can it be done on Windows?
11
votes
2answers
45k views

How do i find out what my IP Address of my MySQL host is?

I have a free domain running at x10hosting (x10.bz), and I want to find out the IP Address of my MySQL host for it, so I can contact the MySQL database from another host. I've already added that host ...
10
votes
4answers
5k views

Is a Network Switch IP-Aware?

I have some very trivial basic questions about networking, but I find varying information on that, so I just wanted to settle this. As far as I understand a Network Switch handles traffic ...
10
votes
5answers
16k views

Why Can't I Reach My Amazon EC2 Instance Via It's “Elastic IP Address?”

The server works fine via the Amazon assigned DNS entry, but I cannot reach it (using a browser) via the Elastic IP address Amazon assigned the box. Ping does not work either. I am trying to confirm ...
10
votes
3answers
833 views

Creative IP/subnet/dns schemes

I've only administered rather small networks (<=25 nodes). Usually I put the gateway .1, dns/proxy as .10, mail at .20, printers at .30-39 and so on and so forth. I never directly use IP addresses ...
10
votes
4answers
10k views

Apache: Limit the Number of Requests/Traffic per IP?

I would like to only allow one IP to use up to, say 1GB, of traffic per day, and if that limit is exceeded, all requests from that IP are then dropped until the next day. However, a more simple ...
10
votes
2answers
583 views

How long are fragmented TCP fragments kept in the TCP server

Suppose that a given TCP fragment is fragmented into two IP datagrams, and that the first datagram arrives to the TCP server, but the second datagram never arrives. After a certain amount of time the ...
10
votes
2answers
792 views

Asterisk for Small Business - Where to Start?

I have been in IT for a long time now doing software development and some system/server administration, but all mostly software-related services. I would like to help set up a small business (~50 ...
9
votes
3answers
14k views

What is this IP address: 169.254.169.254?

I have always noticed an IP something "169.254.x.x" attached even when I am not connected to any network in my Windows operating system. In Linux, when I list my routing table. $ ip route show ...
9
votes
3answers
4k views

Is there an “official” name to the 0.0.0.0 IP address?

As 127.0.0.1 is known as the loopback address, is there a shorter term to refer to 0.0.0.0 other than "the IP address who means all IP address on local machine"?
9
votes
3answers
10k views

How to access a subdomain of an IP address?

I have a website that is accessible only by IP address. How can I access a subdomain of that website?
9
votes
1answer
3k views

Can the value for a NS record be an IP address?

Until today I was used to believe it couldn't. From this page The name field can be any of: A Fully Qualified Domain Name (FQDN) e.g. example.com. (ends with a dot) An unqualfied name ...
9
votes
1answer
9k views

Who (What?!) is “http://1.1.1.1/bmi”? [closed]

I'm not sure if this is the place to ask but I found some pages who contain links in them that start with "http://1.1.1.1/bmi". Who or what is 1.1.1.1? or maybe http://1.1.1.1/bmi has a meaning more ...