Address management methods and apparatus are provided for a node serving as peer group leader for a peer group of nodes in one level of the hierarchy of a PNNI hierarchical network, whereby the peer group leader represents the peer group to one or more neighboring nodes in the next level up of the hierarchy. The peer group leader has a memory (2) for storing peer group topology data (4), comprising address data which is supplied to the peer group leader from nodes in the peer group and represents addresses for access by the network, and peer group leader topology data (5), comprising address data which is supplied to said neighboring nodes by the peer group leader and represents addresses accessible via the peer group. The address management method comprises: checking whether addresses represented by said address data are accessible via the peer group; notifying said neighboring nodes of changes in the accessibility of addresses so identified; and updating said peer group leader topology data (5) in accordance with said changes.