Question

When I call method NetworkInterface.getInetAddresses(), i get the following string:

"fe80:0:0:0:f06c:31b8:cd17:5a44%5"

I wonder what %5 means here? Is it possible to het IPv6 address without this %5?

Answer 1

It’s explained here:

Inet6Adress – Format

The general format for specifying the scope_id is the following:

*IPv6-address%scope_id*

The IPv6-address is a literal IPv6 address as described above. The
scope_id refers to an interface on the local system, and it can be
specified in two ways.

1. As a numeric identifier. This must be a positive integer that identifies the particular interface and scope as understood by the
   system. Usually, the numeric values can be determined through
   administration tools on the system. Each interface may have multiple
   values, one for each scope. If the scope is unspecified, then the
   default value used is zero.

2. As a string. This must be the exact string that is returned by NetworkInterface.getName() for the particular interface in question.
   When an Inet6Address is created in this way, the numeric scope-id is
   determined at the time the object is created by querying the relevant
   NetworkInterface.

Note also, that the numeric scope_id can be retrieved from
Inet6Address instances returned from the NetworkInterface class. This
can be used to find out the current scope ids configured on the
system.