Kevin Warrington

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Using the Loopback Interface

The hosts file is used to map hostnames to ip addresses.

localhost is the hostname for the loopback network interface, in /etc/hosts:

# IPv4 loopback address localhost

# IPv6 loopback address
::1 localhost

# IPv6 link-local address
fe80::1%lo0 localhost

An loopback address is used to send a packet to itself, whereas link-local allows packet transfer between devices on the local link (not routable).

Loopback addresses are often used in web development: localhost project1.local project2.local

They are also used to increase privacy and security. Here is a very helpful resource on the subject.

After updating your hosts file, be sure to clear the directory service cache:

dscacheutil -flushcache