diff --git a/src/Cedar/Virtual.c b/src/Cedar/Virtual.c
index 4fe0c84f..fa2367dc 100644
--- a/src/Cedar/Virtual.c
+++ b/src/Cedar/Virtual.c
@@ -9340,20 +9340,75 @@ UINT ServeDhcpDiscoverEx(VH *v, UCHAR *mac, UINT request_ip, bool is_static_ip)
 		return 0;
 	}
 
+	UINT ret = 0;
 	DHCP_LEASE *d = SearchDhcpLeaseByIp(v, request_ip);
+
 	if (d != NULL)
 	{
-		// The requested IP address is used already
-		return 0;
+		// If an entry for the same IP address already exists,
+		// check whether it is a request from the same MAC address
+		if (Cmp(mac, d->MacAddress, 6) == 0)
+		{
+			// Examine whether the specified IP address is within the range of assignment
+			if (Endian32(v->DhcpIpStart) > Endian32(request_ip) ||
+				Endian32(request_ip) > Endian32(v->DhcpIpEnd))
+			{
+				// Accept if within the range
+				ret = request_ip;
+			}
+		}
+		else {
+			// Duplicated IPV4 address found. The DHCP server replies to DHCPREQUEST with DHCP NAK.
+			char ipstr[MAX_HOST_NAME_LEN + 1] = { 0 };
+			char macstr[128] = { 0 };
+			IPToStr32(ipstr, sizeof(ipstr), request_ip);
+			BinToStr(macstr, sizeof(macstr), d->MacAddress, 6);
+			Debug("Virtual DHC Server: Duplicated IP address detected. Static IP: %s, Used by MAC:%s\n", ipstr, macstr);
+			return ret;
+		}
 	}
-
-	// For static IP, the requested IP address must NOT be within the range of the DHCP pool
-	if (Endian32(request_ip) < Endian32(v->DhcpIpStart) || Endian32(request_ip) > Endian32(v->DhcpIpEnd))
+	else
 	{
-		return request_ip;
+		// Examine whether the specified IP address is within the range of assignment
+		if (Endian32(v->DhcpIpStart) > Endian32(request_ip) ||
+			Endian32(request_ip) > Endian32(v->DhcpIpEnd))
+		{
+			// Accept if within the range
+			ret = request_ip;
+		}
+		else
+		{
+			// Propose an IP in the range since it's a Discover although It is out of range
+		}
+	}
+	if (ret == 0)
+	{
+		// If there is any entry with the same MAC address
+		// that are already registered, use it with priority
+		DHCP_LEASE *d = SearchDhcpLeaseByMac(v, mac);
+
+		if (d != NULL)
+		{
+			// Examine whether the found IP address is in the allocation region
+			if (Endian32(v->DhcpIpStart) > Endian32(d->IpAddress) ||
+				Endian32(d->IpAddress) > Endian32(v->DhcpIpEnd))
+			{
+				// Use the IP address if it's found within the range
+				ret = d->IpAddress;
+			}
+		}
+	}
+	if (ret == 0)
+	{
+		// For static IP, the requested IP address must NOT be within the range of the DHCP pool
+		if (Endian32(v->DhcpIpStart) > Endian32(request_ip) ||
+			Endian32(request_ip) > Endian32(v->DhcpIpEnd))
+		{
+			ret = request_ip;
+		}
 	}
 
-	return 0;
+	return ret;
 }
 
 // Take an appropriate IP addresses that can be assigned newly