127.0.0.1 work on your machine if it's not on the network?
Can these two machine be on the same network?
machine A (192.168.173.11) machine B (192.168.163.11)
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Yes, 127.0.0.1 is called loopback network and is always available. This address points to the machine itself.
EDIT: To answer the second part of the question: Yes, machines A and B can be on the same network (but NOT the same as 127.0.0.1, while loopback is virtual) if the netmask is set properly. Use IP calculator to get what you need.
yes of course, 127.0.0.1 is always available. It is the "localhost", pointing to the machine itself without going to a real net. It is the address of the loopback device and it is present even if no net card is installed (on every modern OS at least).
192.168.x.x is a set of 256 C classes for internal use (see RFC1918) so you can have 65k hosts (as if it would had been a B class). So your machines can stay on the same net and see each others, pay attention to have the right netmask!
If you have a netmask 255.255.0.0 they are on the same net, if you have 255.255.255.0 they don't
Kernel firewall packet filtering could be used to prevent ICMP packets from hitting loopback. In which case a ping would appear to fail (although the interface would still be up).
You could theoretically take it down, but then you would disable sockets. You'd have a seriously stripped down box that would boot up without loopback. It would resemble... MS-DOS!
Yes, you can. In the PC world, 127.0.0.1 is the "loopback" address. On each network card, there is actually a circuit which "loops back" to the network interface, which allows you to test sending/receiving traffic without traffic actually leaving the card. It also allows you to connect to local network services without placing any load onto whatever switch you are connected to. In switches and routing equipment you can actually define the loopback address as any ip address you like, but the functionality is the same.