IP-адрес блока в hostapd сети

Hostapd не имеет дело с IP-адресами, но можно ограничить идентификатор станции.

# Station MAC address -based authentication
# Please note that this kind of access control requires a driver that uses
# hostapd to take care of management frame processing and as such, this can be
# used with driver=hostap or driver=nl80211, but not with driver=madwifi.
# 0 = accept unless in deny list
# 1 = deny unless in accept list
# 2 = use external RADIUS server (accept/deny lists are searched first)
macaddr_acl=1

# Accept/deny lists are read from separate files (containing list of
# MAC addresses, one per line). Use absolute path name to make sure that the
# files can be read on SIGHUP configuration reloads.
accept_mac_file=/etc/hostapd/hostapd.accept
# deny_mac_file=/etc/hostapd/hostapd.deny

Обычно hostapd.accept достаточно для ограничения доступа.