diff --git a/internal/pxe/supervisor.go b/internal/pxe/supervisor.go
index 0fe41df..bbb5250 100644
--- a/internal/pxe/supervisor.go
+++ b/internal/pxe/supervisor.go
@@ -79,11 +79,11 @@ func (s *Supervisor) writeConfig(hosts []model.Host) error {
 	confPath := filepath.Join(s.cfg.RuntimeDir, "dnsmasq.conf")
 	hostsPath := filepath.Join(s.cfg.RuntimeDir, "dhcp-hostsfile")
 
-	var macs []string
+	var lines []string
 	for _, h := range hosts {
-		macs = append(macs, h.MAC)
+		lines = append(lines, h.MAC+",set:known")
 	}
-	if err := os.WriteFile(hostsPath, []byte(strings.Join(macs, "\n")+"\n"), 0o644); err != nil {
+	if err := os.WriteFile(hostsPath, []byte(strings.Join(lines, "\n")+"\n"), 0o644); err != nil {
 		return fmt.Errorf("pxe: write dhcp-hostsfile: %w", err)
 	}