diff --git a/pkg/compute/models/networks.go b/pkg/compute/models/networks.go
index 6b3a7e9b75..907cddabc8 100644
--- a/pkg/compute/models/networks.go
+++ b/pkg/compute/models/networks.go
@@ -1635,6 +1635,10 @@ func (self *SNetwork) validateUpdateData(ctx context.Context, userCred mcclient.
 		if endIp.NetAddr(masklen) != netAddr {
 			return input, httperrors.NewInputParameterError("start, end ip must be in the same subnet")
 		}
+	} else {
+		startIp, _ = netutils.NewIPV4Addr(self.GuestIpStart)
+		endIp, _ = netutils.NewIPV4Addr(self.GuestIpEnd)
+		netAddr = startIp.NetAddr(masklen)
 	}
 
 	for key, ipStr := range map[string]string{