What is Macintosh3-local?

Please can someone clarify the meaning of this:
"Computers on your local network can access your computer at: Macintosh-3.local"
I am having a problem with connectivity, can see another network with an 8 number identifier that seems to interrupt my BT connection and wonder if there is something sharing my network.
The statement above comes up in the Sharing menu and there is also a dialog box that states "Use this name to reach this computer from machines on your local subnet. Local hostname. Macintosh3 -local"
I'm not aware of having a subnet. What is it please?

Macintosh-3.local is your computer's name. All computers have a name for identification purposes. If you were to be sharing a resource like documents or websites from your computer, other computers on your local subnet (or network) would access those resources by using the Macintosh-3.local address to connect to them.

.local addresses are the Macs way of finding each other when on the same subnet (or network). Any flavor of home router will indeed create a network apart from the internet. Private IP networks are 192.168.x.x, 172.16.x.x and 10.0.x.x. These are IP ranges that will not route over the internet thus they are private IP ranges.

Anything outside of you private network will not be able to find your .local computer because of the broadcast domain's limit.

If you have multiple computers connected to your home router they will broadcast their presence on the network so that it makes them easier to provide their resources to each other.

Thank you very much for explaining this, although I find it quite difficult to understand. On my network there are 2 x Windows PCs and this Macbook. Once I was using this Macbook which identifies itself with a different name "C***R********sMacBook", (not Macintosh3 etc), and was asked whether I wanted to connect to this name - although I was already using the computer. The macbook then indicated there was a device attached and operating on my macbook. After a while I was asked if I wanted to disconnect from C***R********sMacBook, which I did - but could not understand. Please could you clarify the relationship between the 2 names: Macintosh-3.local and C***R********sMacBook. Thank you very much.

Please confirm the name of your computer by selecting the sharing icon in system preferences.

Up top will be the computer name. If you select the edit button you should see that the .local extension is present after the computer name.

I cannot tell you for certain what happened in you particular circumstance, but I can tell you that deselecting any options in the sharing section will help from others connecting to you unbeknownst as well as enabling the built in firewall in the security preference pane.

If you have a wireless network and it is unsecured or has "weak" security then it is possible for computers in close proximity to connect to your network and leech it's bandwidth and resources. This might explain rogue computer names that you've discovered. If this is your immediate concern I would address this with your ISP or possibly a local, reliable computer technician.

Without trying to alarm you this all may have been something random. It's just hard to guide someone without knowing their level of expertise when dealing with computer/network questions as it can waste a lot of time.

Hope this helps,..at least points you in a direction.

Thank you for your patience. I have followed System Preference>Sharing and see the .local file extension when I click Edit - just as you said. I have now locked the padlock to prevent further changes and cannot currently see the other network that was causing the problems. The only concern left is that the Selection box for Bluetooth has more defined edges than the others in the list, but I've checked that Bluetooth is Off in the Network box so I'm hoping everything is ok now. Would you recommend activating the FileVault in Security?

Worried Woman said:

Would you recommend activating the FileVault in Security?

Click to expand...

NO! Please don't, it's can cause no end of troubles if you ever need to reinstall OS for any reason, or even perform some basic maintenance.

Macswork - nice assistance.