diff --git src/PVE/INotifyEtcnetOverride.pm src/PVE/INotifyEtcnetOverride.pm
index 2a61264..befbe50 100644
--- src/PVE/INotifyEtcnetOverride.pm
+++ src/PVE/INotifyEtcnetOverride.pm
@@ -686,6 +686,7 @@ my %nm4prefix = qw/
 sub __unwrap_netmask4 {
     my $in=shift;
     my @out;
+    return $in if($in =~ /^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/);
     while (@out<4) {
        if ($in>8) {
            push @out, '255';