diff --git a/IP.pm b/IP.pm
index fac167f..4822f28 100644
--- a/IP.pm
+++ b/IP.pm
@@ -32,7 +32,7 @@
 );
 require Exporter;
 
-@EXPORT_OK = qw(Compact Coalesce Zero Zeros Ones V4mask V4net netlimit);
+@EXPORT_OK = qw(Compact Coalesce Zero Zeros Ones V4mask V4net Exclude netlimit);
 @EXPORT_FAIL = qw($_netlimit);
 
 @ISA = qw(Exporter NetAddr::IP::Lite);
@@ -58,6 +58,7 @@
 	Ones
 	V4mask
 	V4net
+	Exclude
 	netlimit
 	:aton		DEPRECATED
 	:lower
@@ -421,6 +422,28 @@
   return &coalesce;
 }
 
+sub Exclude {
+  my @low;
+  my @up;
+  return ([],[]) if $_[0] == $_[1];
+  my ($s1,$s2) = $_[0]->split($_[0]->masklen+1);
+  while ($s1 != $_[1] && $s2 != $_[1]) {
+    if ($_[1]->within($s1)) {
+      push @up, $s2;
+      ($s1,$s2) = $s1->split($s1->masklen+1);
+    } elsif ($_[1]->within($s2)) {
+      push @low, $s1;
+      ($s1,$s2) = $s2->split($s2->masklen+1);
+    } else {
+      croak("exclude error: $_[1] is not contained in $_[0]");
+    }
+  }
+  push @up, $s2 if $s1 == $_[1];
+  push @low, $s1 if $s2 == $_[1];
+  @up = reverse @up;
+  return (\@low, \@up);
+}
+
 sub hostenumref($) {
   my $r = _splitref(0,$_[0]);
   unless ((notcontiguous($_[0]->{mask}))[1] == 128 ||
diff --git a/t/v4-exclude.t b/t/v4-exclude.t
new file mode 100644
index 0000000..1fb6c37
--- /dev/null
+++ b/t/v4-exclude.t
@@ -0,0 +1,41 @@
+use NetAddr::IP qw(Exclude);
+
+my @r = (
+	['10.0.0.0/8','10.0.0.0/9', [], ['10.128.0.0/9']],
+	['10.0.0.0/8','10.0.0.0/8', [], []],
+	['10.0.0.0/8','10.128.0.0/9', ['10.0.0.0/9'], []],
+	['10.0.0.0/8','10.128.0.0/10', ['10.0.0.0/9'], ['10.192.0.0/10']],
+	['10.0.0.0/8','10.0.0.0/32', [], ['10.0.0.1/32','10.0.0.2/31','10.0.0.4/30','10.0.0.8/29','10.0.0.16/28','10.0.0.32/27','10.0.0.64/26','10.0.0.128/25','10.0.1.0/24','10.0.2.0/23','10.0.4.0/22','10.0.8.0/21','10.0.16.0/20','10.0.32.0/19','10.0.64.0/18','10.0.128.0/17','10.1.0.0/16','10.2.0.0/15','10.4.0.0/14','10.8.0.0/13','10.16.0.0/12','10.32.0.0/11','10.64.0.0/10','10.128.0.0/9']],
+	['192.168.0.0/24','192.168.0.255/32',['192.168.0.0/25','192.168.0.128/26','192.168.0.192/27','192.168.0.224/28','192.168.0.240/29','192.168.0.248/30','192.168.0.252/31','192.168.0.254/32'],[]],
+	['192.168.0.0/23','192.168.0.127/32',['192.168.0.0/26','192.168.0.64/27','192.168.0.96/28','192.168.0.112/29','192.168.0.120/30','192.168.0.124/31','192.168.0.126/32'],['192.168.0.128/25','192.168.1.0/24']],
+	['1.2.3.4/32','1.2.3.4/32',[],[]],
+	['0.0.0.0/0','0.0.0.0/32',[],['0.0.0.1/32','0.0.0.2/31','0.0.0.4/30','0.0.0.8/29','0.0.0.16/28','0.0.0.32/27','0.0.0.64/26','0.0.0.128/25','0.0.1.0/24','0.0.2.0/23','0.0.4.0/22','0.0.8.0/21','0.0.16.0/20','0.0.32.0/19','0.0.64.0/18','0.0.128.0/17','0.1.0.0/16','0.2.0.0/15','0.4.0.0/14','0.8.0.0/13','0.16.0.0/12','0.32.0.0/11','0.64.0.0/10','0.128.0.0/9','1.0.0.0/8','2.0.0.0/7','4.0.0.0/6','8.0.0.0/5','16.0.0.0/4','32.0.0.0/3','64.0.0.0/2','128.0.0.0/1']],
+);
+
+print "1..9\n";
+
+my $num = 0;
+foreach my $case (@r) {
+	$num++;
+	my ($low, $up) = Exclude(NetAddr::IP->new($case->[0]), NetAddr::IP->new($case->[1]));
+	my $ex_low = $case->[2];
+	my $ex_up = $case->[3];
+
+	unless (scalar(@$low) == scalar(@$ex_low) && scalar(@$up) == scalar(@$ex_up)) {
+		print "not ok $num\n";
+		next;
+	}
+	for (my $i=0; $i < @$low; $i++) {
+		if (@$low[$i] != NetAddr::IP->new(@$ex_low[$i])) {
+			print "not ok $num\n";
+			next;
+		}
+	}
+	for (my $i=0; $i < @$up; $i++) {
+		if (@$up[$i] != NetAddr::IP->new(@$ex_up[$i])) {
+			print "not ok $num\n";
+			next;
+		}
+	}
+	print "ok $num\n";
+}