IPv6 stateless DHCP active clients equals zero

When configuring a Cisco IOS device as a DHCPv6 server, and when configuring DHCPv6 pools for use with stateless autoconfiguration, the IOS router will always show a value of zero for the number or active clients.

For example, this output comes from an IOS router that has been configured with two DHCPv6 pools, one that serves a stateful, and another that serves a stateless DHCPv6 configuration. In this topology, each pool has already delivered DHCP information to a single host.

DHCPV6#show ipv6 dhcp pool
DHCPv6 pool: STATEFUL
  Address allocation prefix: 2001:1111:1111:1111::/64 valid 172800 preferred 86400 (1 in use, 0 conflicts)
  DNS server: 2001:4860:4860::8888
  Domain name: NETWORKLESSONS.LOCAL
  Active clients: 1
DHCPv6 pool: STATELESS
  DNS server: 2001:4860:4860::8888
  Domain name: NETWORKLESSONS.LOCAL
  Active clients: 0

The pool named STATELESS has zero active clients, even though it has provided DNS information to a client.

However, because the DHCP server does not actually manage IPv6 addresses for those hosts that obtain their IPv6 addresses via a stateless autoconfiguration, they are not considered clients by the DHCP server. Therefore, any DHCPv6 pools that are serving stateless DHCP hosts, the active client value will remain zero.

https://networklessons.com/ipv6/cisco-dhcpv6-server-configuration/