Zone IDs for Link-Local and Site-Local Addresses
Link-local and site-local addresses are not unique within an organization intranet. Link-local addresses can be duplicated per link (subnet). Site-local addresses can be duplicated per site. Therefore, when specifying a link-local destination address, you must specify the link on which the destination is located. For a site-local destination address when you are using multiple sites, you must specify the site in which the destination is located. You use a zone ID to specify the portion or zone of the network on which the destination can be reached. In the Ping, Tracert, and Pathping commands, the syntax for specifying a zone ID is IPv6Address%ZoneID.
For link-local destinations, ZoneID is typically equal to the interface index of the interface attached to the link on which the destination is located. The interface index is an internal number assigned to an IPv6 interface that is visible from the display of the netsh interface ipv6 show interface command. For site-local addresses, ZoneID is equal to the site number that is visible from the display of the netsh interface ipv6 show address level=verbose command. If multiple sites are not being used, a zone ID for site-local addresses is not required. The ZoneID parameter is not needed when the destination is a global unicast address.