--- services.inc	2020-04-03 01:09:42.381635000 -0500
+++ services.inc.dhcrelay-fix	2020-04-03 01:09:48.595046000 -0500
@@ -1779,22 +1779,36 @@
 	}
 	$srvifaces = array_unique($srvifaces);
 
+	/* If relays are on subnets that also serves clients, we need to move them to their own array */
+	$srvrelayifs = array();
+	$srvrelayifs = array_intersect($dhcrelayifs, $srvifaces);
+	$srvifaces = array_diff($srvifaces, $srvrelayifs);
+	$dhcrelayifs = array_diff($dhcrelayifs, $srvrelayifs);
+
 	/* The server interface(s) should not be in this list */
 	$dhcrelayifs = array_diff($dhcrelayifs, $srvifaces);
 
 	/* fire up dhcrelay */
-	if (empty($dhcrelayifs)) {
+	if (empty($dhcrelayifs) && empty($srvrelayifs)) {
 		log_error(gettext("No suitable downstream interfaces found for running dhcrelay!"));
 		return; /* XXX */
 	}
-	if (empty($srvifaces)) {
+	if (empty($srvifaces) && empty($srvrelayifs)) {
 		log_error(gettext("No suitable upstream interfaces found for running dhcrelay!"));
 		return; /* XXX */
 	}
 
 	$cmd = "/usr/local/sbin/dhcrelay";
-	$cmd .= " -id " . implode(" -id ", $dhcrelayifs);
-	$cmd .= " -iu " . implode(" -iu ", $srvifaces);
+
+	if (!empty($dhcrelayifs)) {
+		$cmd .= " -id " . implode(" -id ", $dhcrelayifs);
+	}
+	if (!empty($srvifaces)) {
+		$cmd .= " -iu " . implode(" -iu ", $srvifaces);
+	}
+	if (!empty($srvrelayifs)) {
+		$cmd .= " -i " . implode(" -i ", $srvrelayifs);
+	}
 
 	if (isset($dhcrelaycfg['agentoption'])) {
 		$cmd .= " -a -m replace";