diff --git a/ip-allocator/storage.go b/ip-allocator/storage.go
new file mode 100644
index 0000000..26be353
--- /dev/null
+++ b/ip-allocator/storage.go
@@ -0,0 +1,87 @@
+package main
+
+type Storage interface {
+	Init(start string, count uint) error
+	Get(mac string) (string, error)
+	GetAll() map[string]string
+	Put(mac, ip string) error
+	Remove(mac string) (string, error)
+	Dequeue() (string, error)
+	Enqueue(ip string) error
+}
+
+type MemoryStorage struct {
+	allocated               map[string]IPv4
+	available               []IPv4
+	readIdx, writeIdx, size uint
+}
+
+func (s *MemoryStorage) Init(start string, count uint) error {
+	ip, err := ParseIP(start)
+	if err != nil {
+		return err
+	}
+	s.readIdx = 0
+	s.writeIdx = 0
+	s.size = count
+	s.allocated = make(map[string]IPv4)
+	s.available = make([]IPv4, count)
+	for i := uint(0); i < count; i += 1 {
+		s.available[i] = ip
+		ip, err = ip.Next()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *MemoryStorage) Get(mac string) (string, error) {
+	ip, ok := s.allocated[mac]
+	if !ok {
+		return "", nil
+	}
+	return ip.String(), nil
+}
+
+func (s *MemoryStorage) GetAll() map[string]string {
+	all := make(map[string]string)
+	for k, v := range s.allocated {
+		all[k] = v.String()
+	}
+	return all
+}
+
+func (s *MemoryStorage) Put(mac, ip string) error {
+	data, err := ParseIP(ip)
+	if err != nil {
+		return err
+	}
+	s.allocated[mac] = data
+	return nil
+}
+
+func (s *MemoryStorage) Remove(mac string) (string, error) {
+	ip, ok := s.allocated[mac]
+	if !ok {
+		return "", nil
+	}
+	delete(s.allocated, mac)
+	return ip.String(), nil
+}
+
+func (s *MemoryStorage) Dequeue() (string, error) {
+	ip := s.available[s.readIdx]
+	s.readIdx = (s.readIdx + 1) % s.size
+	return ip.String(), nil
+}
+
+func (s *MemoryStorage) Enqueue(ip string) error {
+	data, err := ParseIP(ip)
+	if err != nil {
+		return err
+	}
+	s.available[s.writeIdx] = data
+	s.writeIdx = (s.writeIdx + 1) % s.size
+	return nil
+}