This document describes an IPv6 network attachment detection mechanism in which access routers disseminate the identifiers of on- link access points reported by hosts. By caching the identifiers, hosts assess the likelihood of an L3 link change right after an access point change. The hosts are hence able to quickly determine whether an existing IP address configuration can be reused or a new one should be acquired. The mechanism aims to achieve fast L3 connectivity re-establishment with less signaling overhead.