diff --git a/lib/SNMP/Info/Layer3/DLink.pm b/lib/SNMP/Info/Layer3/DLink.pm
index d30533e8..7105193f 100644
--- a/lib/SNMP/Info/Layer3/DLink.pm
+++ b/lib/SNMP/Info/Layer3/DLink.pm
@@ -32,7 +32,6 @@ use strict;
 use warnings;
 use Exporter;
 use SNMP::Info::Layer3;
-use Data::Dumper;
 
 @SNMP::Info::Layer3::DLink::ISA       = qw/SNMP::Info::Layer3 Exporter/;
 @SNMP::Info::Layer3::DLink::EXPORT_OK = qw//;
@@ -75,10 +74,22 @@ $VERSION = '3.70-135';
 
 %MUNGE = ( %SNMP::Info::Layer3::MUNGE, );
 
+sub norm($) {
+    my $var = shift;
+    return norm_hash($var) if ref $var eq 'HASH';
+    return $var if defined $var and $var !~ /^\s*$/ and $var !~ 'NOSUCHOBJECT';
+}
+
+sub norm_hash {
+    my $hash = shift;
+    return $hash->{0} if $hash->{0} !~ /^\s*$/ and $hash->{0} !~ 'NOSUCHOBJECT';
+    print "norm_hash return undef\n";
+}
+
 sub model {
     my $dlink=shift;
-    my $hw = $dlink->hwver() || undef;
-    return $dlink->description() . ' HW:' . $hw if defined($hw);
+    my $hw = norm($dlink->hwver()) || undef;
+    return $dlink->description() . ' HW:' . $hw if norm($hw);
     return $dlink->description();
 }
 
@@ -108,45 +119,45 @@ sub os_ver {
     my $id = $obj->id();
 
 	#Due to the zoo of MIB from DLink by 1210 series
-	$os_ver = $obj->session()->get($id.'.1.3.0') if $model =~ /1210/;
+	$os_ver = norm($obj->session()->get($id.'.1.3.0')) if $model =~ /1210/;
 
     while (not defined $os_ver) {
-        $os_ver = $obj->dlink_fw();
-        last if defined $os_ver;
+        $os_ver = norm($obj->dlink_fw());
+        last if norm($os_ver);
 
-        $os_ver = $obj->session()->get('enterprises.171.10.94.89.89.2.4.0');
+        $os_ver = norm($$obj->session()->get('enterprises.171.10.94.89.89.2.4.0'));
         last;
     }
 
     my $brom = $obj->brom();
-    $os_ver .= ' bootrom:' . $brom if defined $brom;
+    $os_ver .= ' bootrom:' . $brom if norm($brom) and norm($os_ver);
 
-    return $os_ver if defined $os_ver;
+    return $os_ver if norm($os_ver);
 }
 
 sub serial {
-    my $dlink = shift;
-    my $model = $dlink->model();
-    my $id = $dlink->id();
+    my $obj = shift;
+    my $model = $obj->model();
+    my $id = $obj->id();
     my $serial;
     if ($model =~ /1210/) {
 	#Due to the zoo of MIB from DLink by 1210 series
-	$serial->{0} = $dlink->session()->get($id.'.1.30.0');
+	$serial = norm($obj->session()->get($id.'.1.30.0'));
     } else {
-	$serial = $dlink->dlink_serial_no();
+	$serial = norm($obj->dlink_serial_no());
     }
 
-    return $serial->{0} if ( defined $serial->{0} and $serial->{0} !~ /^\s*$/ and $serial->{0} !~ 'NOSUCHOBJECT' );
-    return $dlink->SUPER::serial();
+    return $serial if norm($serial);
+    return $obj->SUPER::serial();
 }
 
 sub brom {
     my $obj = shift;
     my $brom = undef;
 
-    $brom = $obj->session()->get('enterprises.171.10.94.89.89.2.10.0');
+    $brom = norm($obj->session()->get('enterprises.171.10.94.89.89.2.10.0'));
 
-    return $brom if defined $brom;
+    return $brom if norm($brom);
 }
 
 sub hwver {
@@ -156,25 +167,21 @@ sub hwver {
     my $hw = undef;
 
 	#Due to the zoo of MIB from DLink by 1210 series
-	$hw = $obj->session()->get($id.'.1.2.0') if $model =~ /1210/;
-    $hw = undef if defined $hw and $hw eq 'NOSUCHOBJECT';
+	$hw = norm($obj->session()->get($id.'.1.2.0')) if $model =~ /1210/;
+    $hw = undef if norm($hw);
 
-    while(not defined $hw){
-        $hw = $obj->dlink_hw() || undef;
-        $hw = undef if defined $hw and $hw eq 'NOSUCHOBJECT';
-        last if defined $hw;
+    while(! defined $hw){
+        $hw = norm($obj->dlink_hw());
+        last if norm($hw);
 
-        $hw = $obj->session()->get('rmon.19.3.0') || undef;
-        $hw = undef if defined $hw and $hw eq 'NOSUCHOBJECT';
-        last if defined $hw;
-
-        $hw = $obj->session()->get('enterprises.171.10.94.89.89.2.10.0') || undef;
-        $hw = undef if defined $hw and $hw eq 'NOSUCHOBJECT';
+        $hw = norm($obj->session()->get('rmon.19.3.0'));
+        last if norm($hw);
 
+        $hw = norm($obj->session()->get('enterprises.171.10.94.89.89.2.10.0'));
         last;
     }
 
-    return $hw if defined $hw;
+    return $hw if norm($hw);
 }
 
 sub stp_i_root_port {