diff --git src/PVE/INotifyEtcnetOverride.pm src/PVE/INotifyEtcnetOverride.pm
index 2a61264..cfba5a9 100644
--- src/PVE/INotifyEtcnetOverride.pm
+++ src/PVE/INotifyEtcnetOverride.pm
@@ -658,10 +658,16 @@ sub __read_ipv4address_into {
        chomp ($line);
        if ($line =~ m!^\s*(?:$|#)!) {
            # skip
-       } elsif ($line =~ s!\s*([\d\.]+)/(\d+)\s*!!) {
-           $f->{address} = $1;
-           $f->{netmask} = __unwrap_netmask4($2);
-           __line_broadcast_into($path, $line, $f, 'broadcast');
+        } elsif ($line =~ m!\s*([\d\.]+)/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s*!) { # x.x.x.x/a.b.c.d
+            $f->{address} = $1;
+            $f->{netmask} = $2;
+            $line =~ s!\s*([\d\.]+)/([\d\.]+)\s*!!;
+            __line_broadcast_into($path, $line, $f, 'broadcast');
+        } elsif ($line =~ m!\s*([\d\.]+)/(\d{1,3})\s*!) { # x.x.x.x/yy
+            $f->{address} = $1;
+            $f->{netmask} = __unwrap_netmask4($2);
+            $line =~ s!\s*([\d\.]+)/(\d+)\s*!!;
+            __line_broadcast_into($path, $line, $f, 'broadcast');
        } elsif (__line_broadcast_into($path, $line, $f, 'broadcast')) {
            # parsed
        } else {