Hot answers tagged

112 votes
Accepted

Why does typing an IP address instead of the corresponding domain name not show the website?

Because the proper HTTP Host header is often required to actually get the intended site. It's very common to host multiple web sites on the same IP address and distinguish between them based on the ...
111 votes

How to scan local network for SSH-able computers?

From the command line you could use: sudo nmap -sS -p 22 192.168.10.0/24 Substitute for the local address space on your network. I sometimes use this when I plug in a headless rasberry pi and want ...
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59 votes
Accepted

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

What you're seeing is the Google proxy address. Mobile users with a chrome browser (either Android or iOS) that have the bandwidth management features turned on will often be seen as using one of ...
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52 votes

How to scan local network for SSH-able computers?

nmap -p 22 --open -sV 192.168.178.0/24
  • 648
44 votes
Accepted

Why does this URL with excessive preceding dots resolve to an IP address?

Chrome is interpreting the number 1168951531 as a decimal number, which when represented in hexadecimal is 45ACC8EB. 45ACC8EB in hex is the same as the dotted decimal 69.172.200.235, when you take ...
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43 votes
Accepted

Pinging an IP address responds with different IP

That behavior is actually due to a normal feature of ping and has no relation to your actual hardware. Indeed, prefixing the IP address (or part of it) with a leading zero will cause the number to be ...
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41 votes

In the output of `last`, what does suffix ".d" after an IP address mean?

59.224.XX.178.d is not an IP-address but a hostname, or rather part of it. Last tries to do a reverse lookup and stores both the resulting hostname and ip-address for the remote host. By default the ...
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40 votes
Accepted

How do I use Linux to find unused IP addresses on my network?

Any well-behaved device on an Ethernet LAN is free to ignore nearly any traffic, so PINGs, port scans, and the like are all unreliable. Devices are not, however, free to ignore ARP requests, afaik. ...
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37 votes
Accepted

What is the difference between 0.0.0.0/0 and 0.0.0.0/1?

The 0.0.0.0/0 matches every IP address, whereas 0.0.0.0/1 only matches half of them (0.0.0.0-127.255.255.255) and requires 128.0.0.0/1 as its pair to match the rest (128.0.0.0-255.255.255.255). In ...
  • 44.6k
34 votes

Force local IP traffic to an external interface

As always - I'm a little late - but nowadays one could use network namespaces to isolate the interfaces and prevent any local forwarding (and fiddling with iptables :)). Create namespaces (all done ...
32 votes

What is the difference between Unix sockets and TCP/IP sockets?

What's the difference between Unix socket and TCP/IP socket? A TCP/IP socket is used for communication across TCP/IP networks. A connected TCP socket is identified by the combination of local IP, ...
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32 votes
Accepted

understanding "ip addr change" and "ip addr replace" commands

(I realize this is an old question, but Google brought me here because I was trying to figure out exactly what change and replace do and how they are different). I believe that both replace and ...
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29 votes
Accepted

Are people really going to use public IPv6 addresses on their private networks?

Is that how IPv6 is intended to work? In short, yes. One of the primary reasons for increasing the address space so drastically with IPv6 is to get rid of band-aid technologies like NAT and make ...
  • 16.6k
27 votes

Apache 2.4 restrict URL to certain IPs

The Order, Deny, and Allow options have been replaced in Apache 2.4 with <Directory /var/www/mysite.com/htdocs/public> Require all granted </Directory> You can explicitly restrict ...
  • 391
25 votes

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

Probably they are using Google data compression proxy (https://developer.chrome.com/multidevice/data-compression). And to answer your question (from the same page): As a site owner, how do I ...
  • 17.4k
23 votes

Deny IP address on AWS ELB

A straight forward solution is to use a VPC Network ACL Inbound Rule. This only works if your ELB is in a VPC, but if you've created it in the last few years it should be in the default one. To ban 1....
  • 331
23 votes

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

You can get the user's IP address directly if you simply serve the site over HTTPS. You probably should be doing this anyway - especially since you mentioned these are login and registration pages. ...
  • 1,315
23 votes

Why "Nexthop has invalid gateway" when it seems to be defined?

Perhaps something like: ip route add <gateway IP> dev <interface on which it should be reachable> and then ip route add default via <gateway ip> "Direct connection" can ...
22 votes

How to check IPv6 address via command line?

to show the localy listed ipv6 address one can use ip -6 addr This will show all locally configured ipv6 address including the link-local address. to show just global reachable addresses you can use ...
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22 votes
Accepted

What enables Cloudflare to disable direct IP address access?

There's nothing special in the cloudflare setup. This is just a property of HTTP. When a client opens a URL, there are three important steps: If required, it makes a DNS (or other resolution method)...
22 votes

What is the name of an IP prefix with prefix length 31? (i.e. contains only 2 IP addresses)

A /31 is most often used for creating a point to point link between two networks, since it can do so by only using two addresses. Hence the name, 'linknet' You can read this RFC for more information.
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21 votes

How can I display the IP address of an interface?

As @Manuel mentioned, ifconfig is out of date, and ip is the recommended approach going forward. ip -f inet addr show eth1 and to use @bleater's sed or @Jason H.'s awk to filter the output (...
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21 votes
Accepted

American Users have wrong IP address geolocation

Maxmind is a good service, though occasionally there can be errors, since we're now in the time period where IPv4 blocks are scarce, and are being traded and resold on a gray market. If you do find an ...
21 votes

Are people really going to use public IPv6 addresses on their private networks?

We use public IPv6 addresses in our company network for all devices. We use a stateful firewall on our gateway, that: allows all icmpv6 allows new connections from internal network out allows ...
  • 1,563
21 votes
Accepted

Why do people use 172.x.x.x instead of 192.x.x.x

There are multiple reasons to do so. Your University is probably running this network since back in the days when there were no subnet masks and the private 192.168.x networks were Class C networks, ...
20 votes

How do I use Linux to find unused IP addresses on my network?

Since a device cannot ignore ARP requests, I like to use a tool named arp-scan. It is available in most repositories. When you run the command with the --localnet switch it will give you an overview ...
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20 votes
Accepted

How can we explain CIDR notation with /24 and /32 to a manager?

An ip address consists of four numbers separated with a dot between each. You read it from left to right, and each dot adds a level of detail. This is very similar to a real address, think about: ...
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18 votes

How to bind MySQL server to more than one IP address?

As others have answered, there isn't a way yet to selectively bind to more than one interface. Linux has some TCP tools which make it possible. In this setup, you'd configure mysql to listen on 127.0....
  • 385
18 votes

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

You may try this if using MySQL 5.7 version mysql> SELECT SUBSTRING_INDEX(USER(), '@', -1) AS ip, @@hostname as hostname, @@port as port, DATABASE() as current_database; +-----------+------------...
  • 656
18 votes

How does a router get its IP address assigned?

IANA is the organization responsible for global IP assignments. They assign "blocks" of IP addresses to Regional Internet Registries which are geographically based organizations responsible for ...
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