diff --git a/perl-xCAT/xCAT/Utils.pm b/perl-xCAT/xCAT/Utils.pm
index b02a53730..32f69eb8f 100644
--- a/perl-xCAT/xCAT/Utils.pm
+++ b/perl-xCAT/xCAT/Utils.pm
@@ -3559,7 +3559,10 @@ sub get_site_Master
 =head3 get_ServiceNode
 
      Will get the Service node ( name or ipaddress) as known by the Management
-	 Server or Node for the input nodename or ipadress of the node
+	 Node  or Node for the input nodename or ipadress of the node 
+         which can be a Service Node.
+         If the input node is a Service Node then it's Service node
+         is always the Management Node.
 
      input: list of nodenames and/or node ipaddresses (array ref)
 			service name
@@ -3601,8 +3604,8 @@ sub get_ServiceNode
     my $nodehmtab;
     my $noderestab;
     my $snattribute;
-	my $oshash;
-	my $nodetab;
+    my $oshash;
+    my $nodetab;
     $::ERROR_RC = 0;
 
     # determine if the request is for the service node as known by the MN
@@ -3616,27 +3619,9 @@ sub get_ServiceNode
     {
         $snattribute = "xcatmaster";
     }
-
-    my $master =
-      xCAT::Utils->get_site_Master();    # read the site table, master attrib
-
-   # need better logic here for MIXED CLUSTERS
-	# the NIM primary will be either the site.nimprime attr
-	#	or, if not set, the site.master attr
-	my $nimprime;
-	$nimprime = xCAT::InstUtils->getnimprime();
-  	chomp $nimprime;
-
-	# $master and $nimprime is possible to be the same (MN)
-	# but $master is IP addr, $nimprime is short hostname
-	# this results in %snhash may have two keys duplicated.
-	# so use ip for nimprime.
-
-	my $nimprimeip = xCAT::NetworkUtils->getipaddr($nimprime);
-    $nimprime = $nimprimeip;
-
+    # get site.master this will be the default
+    my $master = xCAT::Utils->get_site_Master();  
     $noderestab = xCAT::Table->new('noderes');
-	$nodetab = xCAT::Table->new('nodetype');
 
     unless ($noderestab)    # no noderes table, use default site.master
     {
@@ -3645,17 +3630,10 @@ sub get_ServiceNode
 
         if ($master)        # use site Master value
         {
-			if ($nodetab) {
-				$oshash = $nodetab->getNodesAttribs(\@node_list, ["os"]);
-			}
 				
             foreach my $node (@node_list)
             {               
-				if ( ($oshash->{$node}->[0]->{os}) && ($oshash->{$node}->[0]->{os} eq "AIX"))  {
-					push @{$snhash{$nimprime}}, $node;
-				} else {
 					push @{$snhash{$master}}, $node;
-				}
             }
         }
         else
@@ -3664,9 +3642,6 @@ sub get_ServiceNode
             $::ERROR_RC = 1;
         }
 
-		if ($nodetab) {
-			$nodetab->close;
-		}
         return \%snhash;
     }
 
@@ -3675,32 +3650,24 @@ sub get_ServiceNode
 
         $nodehash = $noderestab->getNodesAttribs(\@node_list, [$snattribute]);
 
-		$oshash = $nodetab->getNodesAttribs(\@node_list, ["os"]);
 
         foreach my $node (@node_list)
         {
             foreach my $rec (@{$nodehash->{$node}})
             {
-                if ($rec and $rec->{$snattribute})
+                if ($rec and $rec->{$snattribute}) # use noderes.servicenode
                 {
                     my $key = $rec->{$snattribute};
                     push @{$snhash{$key}}, $node;
                 }
-                else
+                else  # use site.master
                 {    
-					if ( ($oshash->{$node}->[0]->{os}) && ($oshash->{$node}->[0]->{os} eq "AIX")) {
-                      if ($nimprime) {
-						push @{$snhash{$nimprime}}, $node;
-					  }
-					} else {
-						push @{$snhash{$master}}, $node;
-					}
+  		  push @{$snhash{$master}}, $node;
                 }
             }
         }
 
         $noderestab->close;
-		$nodetab->close;
         return \%snhash;
 
     }