diff --git a/net/cidr/range.go b/net/cidr/range.go
new file mode 100644
index 0000000..e5c9abd
--- /dev/null
+++ b/net/cidr/range.go
@@ -0,0 +1,37 @@
+package cidr
+
+import (
+	"fmt"
+	"net"
+)
+
+func NewCIDRRanger(cidr string) (CIDRRanger, error) {
+	nIP, nIPNet, err := net.ParseCIDR(cidr)
+	if nil != err {
+		return nil, err
+	}
+
+	switch len(nIP) {
+	case net.IPv4len:
+		cr := &cidrRangeIPv4{
+			cidrNet: nIPNet,
+		}
+		return cr, nil
+	case net.IPv6len:
+		cr := &cidrRangeIPv6{
+			cidrNet: nIPNet,
+		}
+		return cr, nil
+	default:
+		return nil, fmt.Errorf("Net: not supported IP length")
+	}
+}
+
+type CIDRRanger interface {
+	Contains(ip net.IP) bool
+	First() net.IP
+	Last() net.IP
+	Range() []net.IP
+	Broadcast() net.IP
+	Network() net.IP
+}
diff --git a/net/cidr/range_v4.go b/net/cidr/range_v4.go
new file mode 100644
index 0000000..ae814fc
--- /dev/null
+++ b/net/cidr/range_v4.go
@@ -0,0 +1,75 @@
+package cidr
+
+import (
+	"net"
+
+	"git.loafle.net/commons_go/util/net/converter"
+)
+
+type cidrRangeIPv4 struct {
+	cidrNet *net.IPNet
+}
+
+func (cr *cidrRangeIPv4) Contains(ip net.IP) bool {
+	return cr.cidrNet.Contains(ip)
+}
+
+func (cr *cidrRangeIPv4) First() net.IP {
+	nIP := cr.Network()
+	return cr.Next(nIP)
+}
+
+func (cr *cidrRangeIPv4) Last() net.IP {
+	bIP := cr.Broadcast()
+	return cr.Previous(bIP)
+}
+
+func (cr *cidrRangeIPv4) Range() []net.IP {
+	fIP := cr.First()
+	if nil == fIP {
+		return nil
+	}
+	lIP := cr.Last()
+	if nil == lIP {
+		return nil
+	}
+	fNum := converter.IPv4ToInt(fIP.To4())
+	lNum := converter.IPv4ToInt(lIP.To4())
+	r := make([]net.IP, 0)
+	for i := fNum; i <= lNum; i++ {
+		r = append(r, converter.IntToIPv4(i))
+	}
+	return r
+}
+
+func (cr *cidrRangeIPv4) Broadcast() net.IP {
+	ip := cr.cidrNet.IP.To4()
+	bIP := net.IPv4(0, 0, 0, 0).To4()
+	for i := 0; i < len(bIP); i++ {
+		bIP[i] = ip[i] | ^cr.cidrNet.Mask[i]
+	}
+	return bIP
+}
+
+func (cr *cidrRangeIPv4) Network() net.IP {
+	ip := cr.cidrNet.IP.To4()
+	return ip.Mask(cr.cidrNet.Mask)
+}
+
+func (cr *cidrRangeIPv4) Next(ip net.IP) net.IP {
+	nNum := converter.IPv4ToInt(ip.To4()) + 1
+	nIP := converter.IntToIPv4(nNum)
+	if cr.Contains(nIP) {
+		return nIP
+	}
+	return nil
+}
+
+func (cr *cidrRangeIPv4) Previous(ip net.IP) net.IP {
+	nNum := converter.IPv4ToInt(ip.To4()) - 1
+	nIP := converter.IntToIPv4(nNum)
+	if cr.Contains(nIP) {
+		return nIP
+	}
+	return nil
+}
diff --git a/net/cidr/range_v6.go b/net/cidr/range_v6.go
new file mode 100644
index 0000000..4ec8804
--- /dev/null
+++ b/net/cidr/range_v6.go
@@ -0,0 +1,39 @@
+package cidr
+
+import "net"
+
+type cidrRangeIPv6 struct {
+	cidrNet *net.IPNet
+}
+
+func (cr *cidrRangeIPv6) Contains(ip net.IP) bool {
+	return cr.cidrNet.Contains(ip)
+}
+
+func (cr *cidrRangeIPv6) First() net.IP {
+
+}
+
+func (cr *cidrRangeIPv6) Last() net.IP {
+
+}
+
+func (cr *cidrRangeIPv6) Range() []net.IP {
+
+}
+
+func (cr *cidrRangeIPv6) Broadcast() net.IP {
+
+}
+
+func (cr *cidrRangeIPv6) Network() net.IP {
+
+}
+
+func (cr *cidrRangeIPv6) Next(ip net.IP) {
+
+}
+
+func (cr *cidrRangeIPv6) Previous(ip net.IP) {
+
+}
diff --git a/net/converter/ip.go b/net/converter/ip.go
index a70194c..5768225 100644
--- a/net/converter/ip.go
+++ b/net/converter/ip.go
@@ -1,64 +1,17 @@
 package converter
 
 import (
-	"strconv"
-	"strings"
+	"fmt"
+	"net"
 )
 
-func IPToUint64(ip string) uint64 {
-	isV4 := true
-	for i := 0; i < len(ip); i++ {
-		switch ip[i] {
-		case ':':
-			isV4 = false
-			break
-		case '.':
-			isV4 = true
-			break
-		}
+func IPToInt(ip net.IP) (int32, error) {
+	switch len(ip) {
+	case net.IPv4len:
+		return IPv4ToInt(ip), nil
+	case net.IPv6len:
+		return IPv6ToInt(ip), nil
+	default:
+		return 0, fmt.Errorf("Net: not supported IP length")
 	}
-	if !isV4 {
-		return ipv6ToUint64(ip)
-	}
-	return IPV4ToUint64(ip)
-}
-
-func IPV4ToUint64(s string) uint64 {
-	bits := strings.Split(s, ".")
-
-	b0, _ := strconv.Atoi(bits[0])
-	b1, _ := strconv.Atoi(bits[1])
-	b2, _ := strconv.Atoi(bits[2])
-	b3, _ := strconv.Atoi(bits[3])
-
-	var sum uint64
-
-	// left shifting 24,16,8,0 and bitwise OR
-
-	sum += uint64(b0) << 24
-	sum += uint64(b1) << 16
-	sum += uint64(b2) << 8
-	sum += uint64(b3)
-
-	return sum
-}
-
-func ipv6ToUint64(s string) uint64 {
-	bits := strings.Split(s, ":")
-
-	b0, _ := strconv.Atoi(bits[0])
-	b1, _ := strconv.Atoi(bits[1])
-	b2, _ := strconv.Atoi(bits[2])
-	b3, _ := strconv.Atoi(bits[3])
-
-	var sum uint64
-
-	// left shifting 24,16,8,0 and bitwise OR
-
-	sum += uint64(b0) << 24
-	sum += uint64(b1) << 16
-	sum += uint64(b2) << 8
-	sum += uint64(b3)
-
-	return sum
 }
diff --git a/net/converter/ip_v4.go b/net/converter/ip_v4.go
new file mode 100644
index 0000000..88d4efc
--- /dev/null
+++ b/net/converter/ip_v4.go
@@ -0,0 +1,17 @@
+package converter
+
+import (
+	"encoding/binary"
+	"net"
+)
+
+func IPv4ToInt(ip net.IP) int32 {
+	return int32(binary.BigEndian.Uint32(ip.To4()))
+}
+
+func IntToIPv4(n int32) net.IP {
+	b := make([]byte, 4)
+	binary.BigEndian.PutUint32(b, uint32(n))
+	return net.IP(b)
+
+}
diff --git a/net/converter/ip_v6.go b/net/converter/ip_v6.go
new file mode 100644
index 0000000..676ad64
--- /dev/null
+++ b/net/converter/ip_v6.go
@@ -0,0 +1,15 @@
+package converter
+
+import (
+	"net"
+)
+
+// Not implemented
+func IPv6ToInt(ip net.IP) int32 {
+	return 0
+}
+
+// Not implemented
+func IntToIPv6(n int32) net.IP {
+	return nil
+}