diff --git a/net/cidr/range.go b/net/cidr/range.go
index 8871555..9d908ee 100644
--- a/net/cidr/range.go
+++ b/net/cidr/range.go
@@ -32,11 +32,11 @@ type CIDRRanger interface {
 	First() net.IP
 	Last() net.IP
 	Range() []net.IP
-	// (!Contains(startIP) || !Contains(endIP)) return nil
-	// (startIP > endIP) return nil
+	// (!Contains(startIP) || !Contains(endIP)) return error
+	// (startIP > endIP) return error
 	// (nil != startIP && nil != endIP) return (startIP ~ endIP) + include - exclude
 	// (nil == startIP || nil == endIP) return include - exclude
-	Ranges(startIP net.IP, endIP net.IP, include []net.IP, exclude []net.IP) []net.IP
+	Ranges(startIP net.IP, endIP net.IP, include []net.IP, exclude []net.IP) ([]net.IP, error)
 	Broadcast() net.IP
 	Network() net.IP
 	Next(ip net.IP) net.IP
diff --git a/net/cidr/range_v4.go b/net/cidr/range_v4.go
index bb4528d..45f5d42 100644
--- a/net/cidr/range_v4.go
+++ b/net/cidr/range_v4.go
@@ -1,6 +1,7 @@
 package cidr
 
 import (
+	"fmt"
 	"net"
 
 	"git.loafle.net/commons_go/util/net/converter"
@@ -47,21 +48,21 @@ func (cr *cidrRangeIPv4) Range() []net.IP {
 // (startIP > endIP) return nil
 // (nil != startIP && nil != endIP) return (startIP ~ endIP) + include - exclude
 // (nil == startIP || nil == endIP) return include - exclude
-func (cr *cidrRangeIPv4) Ranges(startIP net.IP, endIP net.IP, include []net.IP, exclude []net.IP) []net.IP {
+func (cr *cidrRangeIPv4) Ranges(startIP net.IP, endIP net.IP, include []net.IP, exclude []net.IP) ([]net.IP, error) {
 
 	res := make(map[int32]bool)
 
 	if nil != startIP && nil != endIP {
 		if !cr.Contains(startIP) {
-			return nil
+			return nil, fmt.Errorf("CIDR Range: CIDR not contains start ip[%v]", startIP)
 		}
 		if !cr.Contains(endIP) {
-			return nil
+			return nil, fmt.Errorf("CIDR Range: CIDR not contains end ip[%v]", endIP)
 		}
 		sNum := converter.IPv4ToInt(startIP.To4())
 		eNum := converter.IPv4ToInt(endIP.To4())
 		if sNum > eNum {
-			return nil
+			return nil, fmt.Errorf("CIDR Range: Start IP[%v] must smaller then End IP[%v]", startIP, endIP)
 		}
 		for i := sNum; i <= eNum; i++ {
 			res[i] = true
@@ -91,7 +92,7 @@ func (cr *cidrRangeIPv4) Ranges(startIP net.IP, endIP net.IP, include []net.IP,
 		r = append(r, converter.IntToIPv4(k))
 	}
 
-	return r
+	return r, nil
 }
 
 func (cr *cidrRangeIPv4) Broadcast() net.IP {
diff --git a/net/cidr/range_v6.go b/net/cidr/range_v6.go
index f59f9a9..440ad0b 100644
--- a/net/cidr/range_v6.go
+++ b/net/cidr/range_v6.go
@@ -22,8 +22,8 @@ func (cr *cidrRangeIPv6) Range() []net.IP {
 	return nil
 }
 
-func (cr *cidrRangeIPv6) Ranges(startIP net.IP, endIP net.IP, include []net.IP, exclude []net.IP) []net.IP {
-	return nil
+func (cr *cidrRangeIPv6) Ranges(startIP net.IP, endIP net.IP, include []net.IP, exclude []net.IP) ([]net.IP, error) {
+	return nil, nil
 }
 
 func (cr *cidrRangeIPv6) Broadcast() net.IP {