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 ...
- 35.5k
55
votes
45
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 ...
- 590
41
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 ...
- 49.8k
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. ...
- 80.6k
37
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 ...
34
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, ...
- 4,296
34
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 ...
- 449
30
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 ...
- 16.9k
30
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
...
- 431
28
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....
- 381
25
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 (...
- 663
23
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, ...
- 396
23
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)...
- 336
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.
- 3,023
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 ...
- 1,583
20
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;
+-----------+------------...
- 686
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 ...
- 1,441
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:
...
- 2,179
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
17
votes
How to bind MySQL server to more than one IP address?
Prior to MySQL 8.0.13, --bind-address accepts a single address value,
which may specify a single non-wildcard IP address or host name, or
one of the wildcard address formats that permit listening on ...
- 391
15
votes
Accepted
ssh -R binds to 127.0.0.1 only on remote
While the local optional bind address is at the control of SSH's client side (specified with -L/LocalForward or altered with -g/GatewayPorts in the client's configuration), the remote optional bind ...
- 12.8k
14
votes
Remove/hide client sender ip from postfix?
To remove the sender IP from the Received header for new mail submissions, use the header_checks key instead of the smtp_header_checks option:
header_checks = regexp:/etc/postfix/...
- 6,321
14
votes
Are people really going to use public IPv6 addresses on their private networks?
If there is no need for outside connectivity, then private networks can be used. That is the reason for defining private address space also in IPv6.
NAT is a hack that was invented to delay IPv4 ...
- 37.6k
14
votes
Accepted
Correct Network IP addressing if your users have ability to VPN in
Techspot has A List of Common Default Router IP Addresses that helps with this. Usually home routers uses /24 subnets. Nowadays mobile phones are often used for sharing network connection, so we must ...
- 49.8k
14
votes
2 servers, 1 public IP - Redirect subdomain internally
You should use a reverse proxy (e.g. HAProxy, nginx, squid...) in front of those two servers.
Bind public IP address to the proxy frontend and then use SSL SNI extension to route the traffic by the ...
- 638
14
votes
Why does typing an IP address instead of the corresponding domain name not show the website?
Because usually web servers use "virtual server" technology and are able to answer on your HTTP request within exactly the domain name you request, but not the IP address of the web servers. Thanks to ...
- 149
14
votes
Why "Nexthop has invalid gateway" when it seems to be defined?
A gateway address can only be on a directly connected network. The 10.7.0.0/24 network is not directly connected to your host 10.0.0.2, but is instead separated by another network, which is connected ...
- 248k
14
votes
Accepted
Cannot create nested network namespace
TL;DR: As weird as it seems, this is actually not a network namespace issue, but a mount namespace issue and is to be expected.
You should create all new "ip netns namespaces" (see later for the ...
- 12.8k
13
votes
Why "Nexthop has invalid gateway" when it seems to be defined?
I've also encountered the problem, you need
ip link set LINK_NAME up
be aware that if the link has dependencies on other links, such as veth pair, you also need enable them too.
- 395
Only top scored, non community-wiki answers of a minimum length are eligible