diff --git a/src/network/networkd-dhcp6.c b/src/network/networkd-dhcp6.c
index 3c3794ab87..76f4e4109c 100644
--- a/src/network/networkd-dhcp6.c
+++ b/src/network/networkd-dhcp6.c
@@ -531,13 +531,20 @@ static int dhcp6_pd_get_preferred_prefix(
         }
 
         for (uint64_t n = 0; ; n++) {
+                /* If we do not have an allocation preference just iterate
+                 * through the address space and return the first free prefix. */
+
                 r = dhcp6_pd_calculate_prefix(pd_prefix, pd_prefix_len, n, &prefix);
                 if (r < 0)
                         return log_link_warning_errno(link, r,
                                                       "Couldn't find a suitable prefix. Ran out of address space.");
 
-                /* If we do not have an allocation preference just iterate
-                 * through the address space and return the first free prefix. */
+                /* Do not use explicitly requested subnet IDs. Note that the corresponding link may not
+                 * appear yet. So, we need to check the ID is not used in any .network files. */
+                if (set_contains(link->manager->dhcp6_pd_subnet_ids, &n))
+                        continue;
+
+                /* Check that the prefix is not assigned to another link. */
                 if (link_get_by_dhcp6_pd_prefix(link->manager, &prefix, &assigned_link) < 0 ||
                     assigned_link == link) {
                         *ret = prefix;
@@ -602,8 +609,7 @@ static int dhcp6_pd_distribute_prefix(
                 const struct in6_addr *pd_prefix,
                 uint8_t pd_prefix_len,
                 usec_t lifetime_preferred_usec,
-                usec_t lifetime_valid_usec,
-                bool assign_preferred_subnet_id) {
+                usec_t lifetime_valid_usec) {
 
         Link *link;
         int r;
@@ -626,9 +632,6 @@ static int dhcp6_pd_distribute_prefix(
                 if (link == dhcp6_link && !link->network->dhcp6_pd_assign)
                         continue;
 
-                if (assign_preferred_subnet_id != link_has_preferred_subnet_id(link))
-                        continue;
-
                 r = dhcp6_pd_assign_prefix(link, pd_prefix, pd_prefix_len, lifetime_preferred_usec, lifetime_valid_usec);
                 if (r < 0) {
                         if (link == dhcp6_link)
@@ -978,17 +981,7 @@ static int dhcp6_pd_prefix_acquired(Link *dhcp6_link) {
                                                &pd_prefix,
                                                pd_prefix_len,
                                                lifetime_preferred_usec,
-                                               lifetime_valid_usec,
-                                               true);
-                if (r < 0)
-                        return r;
-
-                r = dhcp6_pd_distribute_prefix(dhcp6_link,
-                                               &pd_prefix,
-                                               pd_prefix_len,
-                                               lifetime_preferred_usec,
-                                               lifetime_valid_usec,
-                                               false);
+                                               lifetime_valid_usec);
                 if (r < 0)
                         return r;
         }
diff --git a/src/network/networkd-manager.c b/src/network/networkd-manager.c
index 2141e20622..a122e08800 100644
--- a/src/network/networkd-manager.c
+++ b/src/network/networkd-manager.c
@@ -502,6 +502,7 @@ Manager* manager_free(Manager *m) {
         m->links_by_dhcp6_pd_prefix = hashmap_free(m->links_by_dhcp6_pd_prefix);
         m->links_by_index = hashmap_free_with_destructor(m->links_by_index, link_unref);
 
+        m->dhcp6_pd_subnet_ids = set_free(m->dhcp6_pd_subnet_ids);
         m->networks = ordered_hashmap_free_with_destructor(m->networks, network_unref);
 
         m->netdevs = hashmap_free_with_destructor(m->netdevs, netdev_unref);
@@ -585,7 +586,7 @@ int manager_load_config(Manager *m) {
         if (r < 0)
                 return r;
 
-        return 0;
+        return manager_build_dhcp6_pd_subnet_ids(m);
 }
 
 bool manager_should_reload(Manager *m) {
diff --git a/src/network/networkd-manager.h b/src/network/networkd-manager.h
index 42b77ee0f5..ae9d5adf1b 100644
--- a/src/network/networkd-manager.h
+++ b/src/network/networkd-manager.h
@@ -52,6 +52,7 @@ struct Manager {
         Hashmap *netdevs;
         OrderedHashmap *networks;
         OrderedSet *address_pools;
+        Set *dhcp6_pd_subnet_ids;
 
         usec_t network_dirs_ts_usec;
 
diff --git a/src/network/networkd-network.c b/src/network/networkd-network.c
index c97998848c..443222f610 100644
--- a/src/network/networkd-network.c
+++ b/src/network/networkd-network.c
@@ -643,7 +643,7 @@ int network_reload(Manager *manager) {
         ordered_hashmap_free_with_destructor(manager->networks, network_unref);
         manager->networks = new_networks;
 
-        return 0;
+        return manager_build_dhcp6_pd_subnet_ids(manager);
 
 failure:
         ordered_hashmap_free_with_destructor(new_networks, network_unref);
@@ -651,6 +651,32 @@ failure:
         return r;
 }
 
+int manager_build_dhcp6_pd_subnet_ids(Manager *manager) {
+        Network *n;
+        int r;
+
+        assert(manager);
+
+        set_clear(manager->dhcp6_pd_subnet_ids);
+
+        ORDERED_HASHMAP_FOREACH(n, manager->networks) {
+                if (n->unmanaged)
+                        continue;
+
+                if (!n->dhcp6_pd)
+                        continue;
+
+                if (n->dhcp6_pd_subnet_id < 0)
+                        continue;
+
+                r = set_ensure_put(&manager->dhcp6_pd_subnet_ids, &uint64_hash_ops, &n->dhcp6_pd_subnet_id);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
 static Network *network_free(Network *network) {
         if (!network)
                 return NULL;
diff --git a/src/network/networkd-network.h b/src/network/networkd-network.h
index 942210470c..2fdd4994c4 100644
--- a/src/network/networkd-network.h
+++ b/src/network/networkd-network.h
@@ -365,6 +365,8 @@ int network_reload(Manager *manager);
 int network_load_one(Manager *manager, OrderedHashmap **networks, const char *filename);
 int network_verify(Network *network);
 
+int manager_build_dhcp6_pd_subnet_ids(Manager *manager);
+
 int network_get_by_name(Manager *manager, const char *name, Network **ret);
 void network_apply_anonymize_if_set(Network *network);