diff --git a/src/sdlan_network.erl b/src/sdlan_network.erl
index 45824cc..50429bf 100644
--- a/src/sdlan_network.erl
+++ b/src/sdlan_network.erl
@@ -228,31 +228,21 @@ handle_call({attach, ChannelPid, ClientId, Mac, Ip, Hostname}, _From,
     %% 添加域名->ip的映射关系
     sdlan_hostname_regedit:insert(Hostname, Domain, Ip),
 
-    OldEndpoint = lookup_endpoint(EndpointTable, Mac),
     %% mac对应的Endpoint存在，并且对应的ip变了，需要通知端上清理arp
-    maybe
-        #endpoint{ip = OldIp} ?= OldEndpoint,
-        true ?= OldIp =/= Ip,
-
-        Event = sdlan_pb:encode_msg(#'SDLEvent'{
-            event = {nat_changed, #'SDLEvent.NatChanged' {
-                mac = Mac,
-                ip = Ip
-            }}
-        }),
-        logger:debug("Event: nat_changed, for attach"),
-
-        broadcast(fun(#endpoint{channel_pid = ChannelPid0}) ->
-            sdlan_quic_channel:send_event(ChannelPid0, Event)
-                  end, [Mac], EndpointTable)
-    end,
-    %% 重复attach需要清理之前的绑定信息；即使IP未变化，也不能保留旧channel。
-    cleanup_endpoint(OldEndpoint, ChannelPid, rebind),
+    maybe_nat_changed(ChannelPid, Mac, Ip, EndpointTable),
 
     ChannelRef = monitor(process, ChannelPid),
     SessionToken = gen_session_token(),
-    Endpoint = #endpoint{channel_pid = ChannelPid, channel_ref = ChannelRef,
-        client_id = ClientId, mac = Mac, ip = Ip, hostname = Hostname, session_token = SessionToken, last_seen = erlang:monotonic_time(second)},
+    Endpoint = #endpoint{
+        channel_pid = ChannelPid,
+        channel_ref = ChannelRef,
+        client_id = ClientId,
+        mac = Mac,
+        ip = Ip,
+        hostname = Hostname,
+        session_token = SessionToken,
+        last_seen = erlang:monotonic_time(second)
+    },
     insert_endpoint(EndpointTable, Mac, Endpoint),
 
     %% 生成对应的分区id
@@ -575,6 +565,28 @@ forward_broadcast_by_ets(NetworkId, Sock, SrcMac, DstMac, Packet) ->
         [NetworkId, sdlan_util:format_mac(SrcMac), sdlan_util:format_mac(DstMac)]),
     {ok, byte_size(Packet)}.
 
+maybe_nat_changed(ChannelPid, Mac, Ip, EndpointTable) ->
+    OldEndpoint = lookup_endpoint(EndpointTable, Mac),
+    %% mac对应的Endpoint存在，并且对应的ip变了，需要通知端上清理arp
+    maybe
+        #endpoint{ip = OldIp} ?= OldEndpoint,
+        true ?= OldIp =/= Ip,
+
+        Event = sdlan_pb:encode_msg(#'SDLEvent'{
+            event = {nat_changed, #'SDLEvent.NatChanged' {
+                mac = Mac,
+                ip = Ip
+            }}
+        }),
+        logger:debug("Event: nat_changed, for attach"),
+
+        broadcast(fun(#endpoint{channel_pid = ChannelPid0}) ->
+            sdlan_quic_channel:send_event(ChannelPid0, Event)
+                  end, [Mac], EndpointTable)
+    end,
+    %% 重复attach需要清理之前的绑定信息；即使IP未变化，也不能保留旧channel。
+    cleanup_endpoint(OldEndpoint, ChannelPid, rebind).
+
 cleanup_endpoint(undefined, _KeepChannelPid, _Reason) ->
     ok;
 cleanup_endpoint(#endpoint{channel_ref = ChannelRef, channel_pid = ChannelPid}, KeepChannelPid, Reason) ->