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

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55
votes
8answers
50k views

What is “anycast” and how is it helpful?

I'd never heard of anycast until a few seconds ago when I read "What are some cool or useful server/networking tricks?". The wikipedia "Anycast" article on it is quite formal and doesn't really evoke ...
33
votes
6answers
13k 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 ...
8
votes
3answers
13k views

How can I do traffic shaping in Linux by IP?

We have a transparent proxy setup. I tried looking for traffic shaping in Linux, and all I could find online was to limit traffic by interface (eth0/eth1...). I need to limit the bandwidth (never ...
14
votes
4answers
22k 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 ...
8
votes
2answers
999 views

Is there anything I can do about someone who has pointed their domain at my ip?

This is kind of a weird request. For some reason whoever owns safeandbuy.com has pointed their domain at my IP address. The reason it's a problem is that I'm having all kinds of crawlers that are ...
20
votes
7answers
33k 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 ...
9
votes
2answers
5k views

How can I send visitors to the closest server using DNS?

Is there a way to localize dns entries? Meaning, that users from asia resolve mydomain.com to another ip than users from usa or europe. This would be helpful to give the users the server nearby. DNS ...
6
votes
2answers
786 views

Failed SPF for email imported to Gmail because of client IP instead of server's in message when sent through SMTP from one local box to another

We have a linux (Debian) VPS with domain (let's say example.com with MX mail.example.com) that has SPF set up. There is dovecot+exim running. There is also Direct Admin on top of that. When I send a ...
140
votes
4answers
141k 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 ...
164
votes
5answers
258k 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.
20
votes
8answers
19k 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 ...
5
votes
5answers
5k views

Another domain name pointing to my server IP?

I was checking out my reverse-DNS entry of my domain the other day which is run from a dedicated server. I noticed that another person/company had their domain pointing to my server? I have no idea ...
6
votes
5answers
7k views

Apache virtual host based on *source* IP

Is it possible to configure Apache for different virtual hosts based on the source IP? (i.e. same interface, same hostname, but two different virtual hosts, with different content, based on source IP....
0
votes
5answers
657 views

Many domains/sites hosted on same server, CNAME alternatives to avoid writing same IP in DNS?

I have many sites (each one with its own domain) all on the same cPanel hosted server (let's say server IP is 1.1.1.1 and server main domain is myserver.com) All these domains use third party DNS (...
59
votes
3answers
99k 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 ...
31
votes
7answers
47k 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?
20
votes
1answer
2k 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 ...
10
votes
3answers
1k 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 ...
20
votes
3answers
31k 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 "...
11
votes
2answers
21k views

Nginx - How to redirect users with certain IP to special page

I run quite a big image gallery and there are 5 visitors that create an enormous amount of traffic by downloading the whole site every day using webcopiers. Those visitors have static IPs as it seems. ...
4
votes
5answers
5k views

IP/Process based bandwidth usage stats tool for linux

I'm looking for a simple tool to report server bandwidth usage based on IP/Process. The reason for that is one of our servers is "bleeding" bandwidth and there is a need to find out where it's going. ...
4
votes
4answers
9k views

What are the implications of expanding an internal subnet mask?

Our network is currently working on a 192.168.0.x subnet, all controlled through DHCP, except for the few main servers who have hard-configured IP address settings. What would I kill if I changed the ...
11
votes
2answers
2k 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?
13
votes
6answers
34k 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 ...
10
votes
1answer
4k 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 (...
6
votes
4answers
510 views

How to know what user belongs to what ip on debian

is there a way to get an overview of users logged in on my server and the ip they are connecting from ? I have the IP already, I want the user that is associated with it :)
5
votes
1answer
552 views

Some visitors cannot access my website

I am receiving some reports from different clients in Spain, US and France that they cannot access my website, https://www.ultreyatours.com. They get a ERR_NAME_NOT_RESOLVED error saying the server ...
3
votes
6answers
1k views

Finding all domain names that resolve to the same ip?

Lately I've been tracking a spammer on craigslist. I recently discovered that he's added a new technique to his arsenal, he registered a whole bunch of domain names but they all resolve to the same ip ...
2
votes
3answers
1k views

In Apache, is there a way to limit the number of new connections per second/hour/day?

To clarify, I do not wish to limit the number of simultaneous connections, nor do I want to limit the number of HTTP requests. I only want to limit the number of NEW connections per IP. I want to do ...
2
votes
1answer
657 views

How come I can't redirect TCP ports on this wireless router?

I am configuring a router to redirect TCP port 5900 (yes, this is for VNC) to a specific IP address on the network. Here is what I have: From a local computer on the same network, I can telnet to ...
1
vote
2answers
6k views

Centos: multiple IP addresses

I just bought 10 extra IPs from my host. How do I point these at my CentOS 5 server?
0
votes
2answers
7k views

How to route UDP traffic from one public IP (linux) to another public IP(Windows)

I want to prevent direct access of my Windows Machine and want to expose some programs running on it via my Linux Machine (which again is accessible by a Public IP). Is there a way where-in I can ...
3
votes
4answers
172 views

Linking Domain Names to Port Numbers

I have a [game] server (CentOS) that has about 10 used ports. For one game in particular, I have 2 servers: a private one and a public one. The IP for them is the same, so to differentuate between ...
2
votes
1answer
2k views

Under what circumstances will Linux ignore the route table when choosing the MAC address for an outbound frame?

While debugging a problem with the networking configuration for a set of virtual machines running under KVM, I discovered a circumstance where the kernel in the guest VM has decided to stamp the ...
2
votes
1answer
3k views

Is it possible to connect 2 networks with same IP range?

I have two networks with the same IP addresses in use and I need to connect them. I have a third network between the two to connect them but I need to know : - is it possible to communicate iof the ...
64
votes
6answers
497k 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 ...
40
votes
14answers
15k 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 ...
14
votes
3answers
46k views

How can I get the IP address of a remote desktop client? And how can I trigger a shell command upon RDP connect?

Is there a way to determine the IP address of a remote desktop client using PowerShell (or some other method) on the server? (Windows Server 2008 R2 x64 is what I'm using) EDIT: I find that I can ...
17
votes
5answers
112k 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
3answers
6k 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"?
15
votes
4answers
22k 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 ...
34
votes
5answers
98k 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?
15
votes
5answers
29k 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 ...
8
votes
6answers
23k views

Is it possible to match an internal IP address to a switch port?

I'm trying to find a computer that has a certain IP address on our internal network. I have identified the computer name from DNS, but in this case it does not help me. Just wondering if I can ...
8
votes
2answers
8k views

ip address scope parameter

In Linux, the command ip address add [...] has a scope argument. The man page says that the scope is "the scope of the area where this address is valid". Follows the list of legal scopes: global ...
35
votes
5answers
5k 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 ...
8
votes
1answer
6k views

Remove/hide client sender ip from postfix?

I'm trying to hide the client IP from emails sent from postfix. here is an example of what I mean: Received: from mail.[removed].com (adsl-75-37-61-254.dsl.frs2ca.sbcglobal.net [75.37.61.254]) (...
6
votes
7answers
4k views

Static IP Address assignment vs DHCP address assignment

I manage a small-ish network that consists of less than 70 nodes. The previous system administrators opted to have a dhcp server and manually set dhcp addess. I have opted to rather use dhcp ...
7
votes
4answers
2k views

CIDR Ranges for Everything except RFC1918

I'm looking for a list of CIDR blocks for "The Internet", i.e. everything from 0.0.0.0 to 223.255.255.255, excluding RFC1918 address space of 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 (yes, I know ...
6
votes
3answers
4k views

Changing netmask from /24 to /16 on a Windows 2003 domain

I have a Windows 2003 domain using 192.168.0.0/24 with all static addresses (no dhcp). I want to move to 192.168.0.0/16 because we need more addresses. I understand that we need to change netmask ...