diff --git a/src/etc/inc/interfaces.inc b/src/etc/inc/interfaces.inc
index b2e5b09ad0..f3ee29e37a 100644
--- a/src/etc/inc/interfaces.inc
+++ b/src/etc/inc/interfaces.inc
@@ -868,7 +868,7 @@ function interface_reset($interface, $ifacecfg = false, $suspend = false)
         case 'slaac':
         case 'dhcp6':
             interface_dhcpv6_prepare($interface, $ifcfg, true);
-            killbypid('/var/run/dhcp6c.pid', 'HUP');
+            killbypid("/var/run/dhcp6c.{$device}.pid", 'HUP');
             break;
         case 'idassoc6':
         case 'track6':
@@ -2609,7 +2609,7 @@ function interface_track6_configure($interface, $lancfg, $reload = false)
         case 'dhcp6':
             if ($reload || !isset($lancfg['enable'])) {
                 interface_dhcpv6_prepare($lancfg['track6-interface'], $trackcfg);
-                killbypid('/var/run/dhcp6c.pid', 'HUP');
+                killbypid("/var/run/dhcp6c.{$trackcfg['if']}.pid", 'HUP');
             }
             break;
     }
@@ -2893,15 +2893,16 @@ function interface_dhcpv6_configure($interface, $wancfg)
     }
 
     /* always kill rtsold in case of reconfigure */
-    killbypid('/var/run/rtsold.pid');
+    killbypid("/var/run/rtsold.{$wancfg['if']}.pid");
     @unlink("/tmp/rtsold.{$wancfg['if']}.done");
 
-    $rtsold_frmt = ['/usr/sbin/rtsold -%s -aiu -p %s -A %s -R %s'];
+    $rtsold_frmt = ['/usr/sbin/rtsold -%s -iu -p %s -A %s -R %s %s'];
     $rtsold_args = [
         $settings->dhcp6_debug->isEmpty() ? 'd' : 'D',
-        '/var/run/rtsold.pid',
+        "/var/run/rtsold.{$wancfg['if']}.pid",
         '/usr/local/opnsense/scripts/interfaces/rtsold_script.sh',
         '/usr/local/opnsense/scripts/interfaces/rtsold_resolvconf.sh',
+        $wancfg['if'],
     ];
 
     /* fire up rtsold for IPv6 RAs first */
@@ -2917,28 +2918,6 @@ function interface_dhcpv6_configure($interface, $wancfg)
     }
 }
 
-function interface_dhcpv6_id($interface)
-{
-    global $config;
-
-    /* configuration default */
-    $id = 0;
-
-    if (empty($config['interfaces'])) {
-        return $id;
-    }
-
-    /* detect unique index */
-    foreach (array_keys($config['interfaces']) as $key) {
-        if ($key == $interface) {
-            break;
-        }
-        $id += 1;
-    }
-
-    return $id;
-}
-
 function interface_dhcpv6_prepare($interface, $wancfg, $cleanup = false)
 {
     if (!is_array($wancfg)) {
@@ -2946,7 +2925,6 @@ function interface_dhcpv6_prepare($interface, $wancfg, $cleanup = false)
     }
 
     $settings = new OPNsense\Interfaces\Settings();
-    $id = interface_dhcpv6_id($interface);
     $device = $wancfg['if'];
 
     $dhcp6cconf = "# generated for {$interface} in {$wancfg['ipaddrv6']} mode\n";
@@ -2968,9 +2946,9 @@ function interface_dhcpv6_prepare($interface, $wancfg, $cleanup = false)
             log_msg("DHCP6 config file override does not exist: '{$dhcp6cfile}'", LOG_ERR);
         }
     } elseif (!empty($wancfg['adv_dhcp6_config_advanced'])) {
-        $dhcp6cconf .= DHCP6_Config_File_Advanced($interface, $wancfg, $device, $id);
+        $dhcp6cconf .= DHCP6_Config_File_Advanced($interface, $wancfg, $device);
     } else {
-        $dhcp6cconf .= DHCP6_Config_File_Basic($interface, $wancfg, $device, $id);
+        $dhcp6cconf .= DHCP6_Config_File_Basic($interface, $wancfg, $device);
     }
 
     if (!$cleanup) {
@@ -2978,24 +2956,9 @@ function interface_dhcpv6_prepare($interface, $wancfg, $cleanup = false)
     } else {
         @unlink("/var/etc/dhcp6c.{$device}.conf");
     }
-
-    $dhcp6cconf = '';
-
-    /* merge configs and prepare single instance of dhcp6c for startup */
-    foreach (legacy_config_get_interfaces(['enable' => true, 'virtual' => false]) as $_interface => $_wancfg) {
-        if (empty($_wancfg['ipaddrv6']) || ($_wancfg['ipaddrv6'] != 'dhcp6' && $_wancfg['ipaddrv6'] != 'slaac')) {
-            continue;
-        }
-
-        if (file_exists("/var/etc/dhcp6c.{$_wancfg['if']}.conf")) {
-            $dhcp6cconf .= file_get_contents("/var/etc/dhcp6c.{$_wancfg['if']}.conf");
-        }
-    }
-
-    @file_put_contents('/var/etc/dhcp6c.conf', $dhcp6cconf);
 }
 
-function DHCP6_Config_File_Basic($interface, $wancfg, $wanif, $id = 0)
+function DHCP6_Config_File_Basic($interface, $wancfg, $wanif)
 {
     $dhcp6cconf = '';
 
@@ -3020,7 +2983,7 @@ function DHCP6_Config_File_Basic($interface, $wancfg, $wanif, $id = 0)
                 }
                 $pd_conf .= "  };\n";
 
-                /* XXX $id from dhcp6_assoc_pd */
+                $id = strlen($wancfg['dhcp6_assoc_pd'] ?? '') ? $wancfg['dhcp6_assoc_pd'] : '0';
                 $assoc_pd[$id] = ($assoc_pd[$id] ?? '') . $pd_conf;
             }
 
@@ -3035,25 +2998,26 @@ function DHCP6_Config_File_Basic($interface, $wancfg, $wanif, $id = 0)
                     }
                     $pd_conf .= "  };\n";
 
-                    /* XXX $id from track6_assoc_pd */
+                    $id = strlen($lancfg['track6_assoc_pd'] ?? '') ? $lancfg['track6_assoc_pd'] : '0';
                     $assoc_pd[$id] = ($assoc_pd[$id] ?? '') . $pd_conf;
                 }
             }
+
+            if (!count($assoc_pd)) {
+                /* for backwards compatibility always emit a default PD request */
+                $assoc_pd[0] = '';
+            }
         }
 
         ksort($assoc_pd, SORT_NUMERIC);
 
-        /* for backwards compatibility always emit this PD request */
-        if (!isset($assoc_pd[$id])) {
-            $assoc_pd[$id] = '';
-        }
-
         $dhcp6cconf .= "interface {$wanif} {\n";
 
         if (!isset($wancfg['dhcp6prefixonly'])) {
             /* request non-temporary address */
-            $dhcp6cconf .= "  send ia-na {$id};\n";
+            $dhcp6cconf .= "  send ia-na 0;\n";
         }
+
         if (is_numeric($wancfg['dhcp6-ia-pd-len'])) {
             /* request prefix delegation */
             foreach (array_keys($assoc_pd) as $id) {
@@ -3074,7 +3038,7 @@ function DHCP6_Config_File_Basic($interface, $wancfg, $wanif, $id = 0)
         $dhcp6cconf .= "};\n";
 
         if (!isset($wancfg['dhcp6prefixonly'])) {
-            $dhcp6cconf .= "id-assoc na {$id} { };\n";
+            $dhcp6cconf .= "id-assoc na 0 { };\n";
         }
 
         foreach ($assoc_pd as $i => $pd_conf) {
@@ -3091,7 +3055,7 @@ function DHCP6_Config_File_Basic($interface, $wancfg, $wanif, $id = 0)
     return $dhcp6cconf;
 }
 
-function DHCP6_Config_File_Advanced($interface, $wancfg, $wanif, $id = 0)
+function DHCP6_Config_File_Advanced($interface, $wancfg, $wanif)
 {
     $send_options = "";
 
@@ -3133,7 +3097,7 @@ function DHCP6_Config_File_Advanced($interface, $wancfg, $wanif, $id = 0)
         if (is_numeric($wancfg['adv_dhcp6_id_assoc_statement_address_id'])) {
             $id_assoc_statement_address .= "{$wancfg['adv_dhcp6_id_assoc_statement_address_id']}";
         } else {
-            $id_assoc_statement_address .= $id;
+            $id_assoc_statement_address .= 0; /* only as a fallback */
         }
         $id_assoc_statement_address .= " {\n";
 
@@ -3163,7 +3127,7 @@ function DHCP6_Config_File_Advanced($interface, $wancfg, $wanif, $id = 0)
         if (is_numeric($wancfg['adv_dhcp6_id_assoc_statement_prefix_id'])) {
             $id_assoc_statement_prefix .= "{$wancfg['adv_dhcp6_id_assoc_statement_prefix_id']}";
         } else {
-            $id_assoc_statement_prefix .= $id;
+            $id_assoc_statement_prefix .= 0; /* only as a fallback */
         }
         $id_assoc_statement_prefix .= " {\n";
 
diff --git a/src/opnsense/scripts/interfaces/rtsold_script.sh b/src/opnsense/scripts/interfaces/rtsold_script.sh
index f9e09a89ac..d87ac0f2e1 100755
--- a/src/opnsense/scripts/interfaces/rtsold_script.sh
+++ b/src/opnsense/scripts/interfaces/rtsold_script.sh
@@ -33,17 +33,17 @@ if [ -z "${IFNAME}" ]; then
 fi
 
 if grep -q "^interface ${IFNAME} " /var/etc/radvd.conf; then
-       /usr/bin/logger -t dhcp6c "rtsold_script: rejecting dhcp6c"
+       /usr/bin/logger -t dhcp6c "rtsold_script: rejecting dhcp6c on ${IFNAME}"
        echo "Rejecting own configuration."
        exit 0
 fi
 
+CONFFILE="/var/etc/dhcp6c.${IFNAME}.conf"
+PIDFILE="/var/run/dhcp6c.${IFNAME}.pid"
 DONEFILE="/tmp/rtsold.${IFNAME}.done"
-CONFFILE="/var/etc/dhcp6c.conf"
-PIDFILE="/var/run/dhcp6c.pid"
 
 if [ ! -f "${CONFFILE}" ]; then
-    /usr/bin/logger -t dhcp6c "rtsold_script: skipping dhcp6c"
+    /usr/bin/logger -t dhcp6c "rtsold_script: skipping dhcp6c on ${IFNAME}"
     exit 0
 fi
 
@@ -74,10 +74,10 @@ if [ -f "${PIDFILE}" ]; then
 fi
 
 if [ -f "${PIDFILE}" ]; then
-    /usr/bin/logger -t dhcp6c "rtsold_script: reloading dhcp6c"
+    /usr/bin/logger -t dhcp6c "rtsold_script: reloading dhcp6c on ${IFNAME}"
     /bin/pkill -HUP -F "${PIDFILE}"
 else
-    /usr/bin/logger -t dhcp6c "rtsold_script: starting dhcp6c"
+    /usr/bin/logger -t dhcp6c "rtsold_script: starting dhcp6c on ${IFNAME}"
     /usr/local/sbin/dhcp6c $(get_var EXTRAOPTS) -c "${CONFFILE}" -p "${PIDFILE}"
 fi
 
diff --git a/src/www/interfaces.php b/src/www/interfaces.php
index 4bd4e3027b..7b83bf11ac 100644
--- a/src/www/interfaces.php
+++ b/src/www/interfaces.php
@@ -251,20 +251,31 @@ function validate_track6_idassoc6(&$pconfig, $if)
             if ($track6_prefix_id < 0 || $track6_prefix_id >= $ipv6_num_prefix_ids) {
                 $input_errors[] = gettext("You specified an IPv6 prefix ID that is out of range.");
             }
+            $assoc_pd_ref = '0';
+            if (!empty($pconfig["{$pconfig['type6']}_assoc_pd"]) && ctype_digit($pconfig["{$pconfig['type6']}_assoc_pd"])) {
+                $assoc_pd_ref = $pconfig["{$pconfig['type6']}_assoc_pd"];
+            }
             foreach (link_interface_to_track6($pconfig["{$pconfig['type6']}-interface"]) as $trackif => $trackcfg) {
-                if ($trackif != $if && $trackcfg['track6-prefix-id'] == $track6_prefix_id) {
+                $assoc_pd_link = !empty($trackcfg['track6_assoc_pd']) ? $trackcfg['track6_assoc_pd'] : '0';
+                if ($trackif != $if && $assoc_pd_ref == $assoc_pd_ref && $trackcfg['track6-prefix-id'] == $track6_prefix_id) {
                     $input_errors[] = gettext('You specified an IPv6 prefix ID that is already in use.');
                     break;
                 }
             }
             if (isset($config['interfaces'][$pconfig["{$pconfig['type6']}-interface"]]['dhcp6-prefix-id'])) {
-                if ($config['interfaces'][$pconfig["{$pconfig['type6']}-interface"]]['dhcp6-prefix-id'] == $track6_prefix_id) {
+                $assoc_pd_parent = !empty($config['interfaces'][$pconfig["{$pconfig['type6']}-interface"]]['dhcp6_assoc_pd']) ?
+                    $config['interfaces'][$pconfig["{$pconfig['type6']}-interface"]]['dhcp6_assoc_pd'] : '0';
+                if ($assoc_pd_ref == $assoc_pd_parent && $config['interfaces'][$pconfig["{$pconfig['type6']}-interface"]]['dhcp6-prefix-id'] == $track6_prefix_id) {
                     $input_errors[] = gettext('You specified an IPv6 prefix ID that is already in use.');
                 }
             }
         }
     }
 
+    if (!empty($pconfig["{$pconfig['type6']}_assoc_pd"]) && !ctype_digit($pconfig["{$pconfig['type6']}_assoc_pd"])) {
+        $input_errors[] = gettext('You must enter a valid number for the IPv6 prefix association identity.');
+    }
+
     if (isset($pconfig["{$pconfig['type6']}_ifid--hex"]) && $pconfig["{$pconfig['type6']}_ifid--hex"] != '') {
         if (!ctype_xdigit($pconfig["{$pconfig['type6']}_ifid--hex"])) {
             $input_errors[] = gettext('You must enter a valid hexadecimal number for the IPv6 interface ID.');
@@ -298,6 +309,9 @@ function store_track6_idassoc6(&$new_config, &$pconfig)
     if (isset($pconfig["{$pconfig['type6']}_ifid--hex"]) && ctype_xdigit($pconfig["{$pconfig['type6']}_ifid--hex"])) {
         $new_config['track6_ifid'] = intval($pconfig["{$pconfig['type6']}_ifid--hex"], 16);
     }
+    if (!empty($pconfig["{$pconfig['type6']}_assoc_pd"])) {
+        $new_config['track6_assoc_pd'] = $pconfig["{$pconfig['type6']}_assoc_pd"];
+    }
     if ($pconfig['type6'] == 'track6') {
         /* this is not needed in the new world */
         $new_config['dhcpd6track6allowoverride'] = !empty($pconfig['dhcpd6track6allowoverride']);
@@ -464,6 +478,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
         'dhcp6_ifid',
         'dhcp6_norequest_dns',
         'dhcp6_rapid_commit',
+        'dhcp6_assoc_pd',
         'dhcp6vlanprio',
         'dhcphostname',
         'dhcprejectfrom',
@@ -491,6 +506,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
         'subnetv6',
         'track6-interface',
         'track6-prefix-id',
+        'track6_assoc_pd',
         'track6_ifid',
     ];
     foreach ($std_copy_fieldnames as $fieldname) {
@@ -512,7 +528,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
     $pconfig['dhcpd6track6allowoverride'] = isset($a_interfaces[$if]['dhcpd6track6allowoverride']);
     $pconfig['dhcp6_request_dns'] = empty($pconfig['dhcp6_norequest_dns']);
 
-    foreach(['-interface', '-prefix-id', '-prefix-id--hex', '_ifid', '_ifid--hex'] as $fieldname) {
+    foreach(['-interface', '-prefix-id', '-prefix-id--hex', '_assoc_pd', '_ifid', '_ifid--hex'] as $fieldname) {
         /* only for form consistency */
         $pconfig["idassoc6{$fieldname}"] = $pconfig["track6{$fieldname}"];
     }
@@ -750,14 +766,22 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
                                 $input_errors[] = gettext("You specified an IPv6 prefix ID that is out of range.");
                             }
                         }
+                        $assoc_pd_ref = '0';
+                        if (!empty($pconfig['dhcp6_assoc_pd']) && ctype_digit($pconfig['dhcp6_assoc_pd'])) {
+                            $assoc_pd_ref = $pconfig['dhcp6_assoc_pd'];
+                        }
                         foreach (link_interface_to_track6($pconfig['track6-interface']) as $trackif => $trackcfg) {
-                            if ($trackcfg['track6-prefix-id'] == $dhcp6_prefix_id) {
+                            $assoc_pd_link = !empty($trackcfg['track6_assoc_pd']) ? $trackcfg['track6_assoc_pd'] : '0';
+                            if ($assoc_pd_ref == $assoc_pd_link && $trackcfg['track6-prefix-id'] == $dhcp6_prefix_id) {
                                 $input_errors[] = gettext('You specified an IPv6 prefix ID that is already in use.');
                                 break;
                             }
                         }
                     }
                 }
+                if (!empty($pconfig['dhcp6_assoc_pd']) && !ctype_digit($pconfig['dhcp6_assoc_pd'])) {
+                    $input_errors[] = gettext('You must enter a valid number for the IPv6 prefix association identity.');
+                }
                 if (isset($pconfig['dhcp6_ifid--hex']) && $pconfig['dhcp6_ifid--hex'] != '') {
                     if (!ctype_xdigit($pconfig['dhcp6_ifid--hex'])) {
                         $input_errors[] = gettext('You must enter a valid hexadecimal number for the IPv6 interface ID.');
@@ -1123,6 +1147,9 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
                     if (!empty($pconfig['dhcp6_rapid_commit'])) {
                         $new_config['dhcp6_rapid_commit'] = true;
                     }
+                    if (!empty($pconfig['dhcp6_assoc_pd'])) {
+                        $new_config['dhcp6_assoc_pd'] = $pconfig['dhcp6_assoc_pd'];
+                    }
                     $new_config['adv_dhcp6_interface_statement_send_options'] = $pconfig['adv_dhcp6_interface_statement_send_options'];
                     $new_config['adv_dhcp6_interface_statement_request_options'] = $pconfig['adv_dhcp6_interface_statement_request_options'];
                     $new_config['adv_dhcp6_interface_statement_information_only_enable'] = $pconfig['adv_dhcp6_interface_statement_information_only_enable'];
@@ -2390,6 +2417,15 @@ include("head.inc");
                             </div>
                           </td>
                         </tr>
+                        <tr class="dhcpv6_basic">
+                          <td><a id="help_for_dhcp6_assoc_pd" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?= gettext('Optional IA-PD ID') ?></td>
+                          <td>
+                            <input name="dhcp6_assoc_pd" type="text" id="dhcp6_assoc_pd" value="<?= html_safe($pconfig['dhcp6_assoc_pd']) ?>" />
+                            <div class="hidden" data-for="help_for_dhcp6_assoc_pd">
+                              <?= gettext('The ID to use for prefix request identity association if required to be non-zero.') ?>
+                            </div>
+                          </td>
+                        </tr>
                         <tr class="dhcpv6_advanced">
                           <td><a id="help_for_dhcp6_intf_stmt" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?=gettext("Interface Statement");?></td>
                           <td>
@@ -2619,6 +2655,15 @@ include("head.inc");
                             </div>
                           </td>
                         </tr>
+                        <tr>
+                          <td><a id="help_for_idassoc6_assoc_pd" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?= gettext('Optional IA-PD ID') ?></td>
+                          <td>
+                            <input name="idassoc6_assoc_pd" type="text" id="idassoc6_assoc_pd" value="<?= html_safe($pconfig['idassoc6_assoc_pd']) ?>" />
+                            <div class="hidden" data-for="help_for_idassoc6_assoc_pd">
+                              <?= gettext('The ID to use for prefix request identity association if required to be non-zero.') ?>
+                            </div>
+                          </td>
+                        </tr>
                       </tbody>
                     </table>
                   </div>
@@ -2675,6 +2720,15 @@ include("head.inc");
                             </div>
                           </td>
                         </tr>
+                        <tr>
+                          <td><a id="help_for_track6_assoc_pd" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?= gettext('Optional IA-PD ID') ?></td>
+                          <td>
+                            <input name="track6_assoc_pd" type="text" id="track6_assoc_pd" value="<?= html_safe($pconfig['track6_assoc_pd']) ?>" />
+                            <div class="hidden" data-for="help_for_track6_assoc_pd">
+                              <?= gettext('The ID to use for prefix request identity association if required to be non-zero.') ?>
+                            </div>
+                          </td>
+                        </tr>
                         <tr>
                           <td><a id="help_for_dhcpd6_opt" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?= gettext('Manual configuration') ?></td>
                           <td>