diff --git a/isisd/isis_csm.c b/isisd/isis_csm.c
new file mode 100644
index 0000000..2282bbc
--- /dev/null
+++ b/isisd/isis_csm.c
@@ -0,0 +1,186 @@
+/*
+ * IS-IS Rout(e)ing protocol - isis_csm.c
+ *                             IS-IS circuit state machine
+ * Copyright (C) 2001,2002    Sampo Saaristo
+ *                            Tampere University of Technology      
+ *                            Institute of Communications Engineering
+ *
+ * This program is free software; you can redistribute it and/or modify it 
+ * under the terms of the GNU General Public Licenseas published by the Free 
+ * Software Foundation; either version 2 of the License, or (at your option) 
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,but WITHOUT 
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for 
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along 
+ * with this program; if not, write to the Free Software Foundation, Inc., 
+ * 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#include <zebra.h>
+#include <net/ethernet.h>
+
+#include "log.h"
+#include "memory.h"
+#include "if.h"
+#include "linklist.h"
+#include "command.h"
+#include "thread.h"
+#include "hash.h"
+#include "prefix.h"
+#include "stream.h"
+
+#include "isisd/dict.h"
+#include "isisd/include-netbsd/iso.h"
+#include "isisd/isis_constants.h"
+#include "isisd/isis_common.h"
+#include "isisd/isis_circuit.h"
+#include "isisd/isis_tlv.h"
+#include "isisd/isis_lsp.h"
+#include "isisd/isis_pdu.h"
+#include "isisd/isis_network.h"
+#include "isisd/isis_misc.h"
+#include "isisd/isis_constants.h"
+#include "isisd/isis_adjacency.h"
+#include "isisd/isis_dr.h"
+#include "isisd/isis_flags.h"
+#include "isisd/isisd.h"
+#include "isisd/isis_csm.h"
+#include "isisd/isis_events.h"
+
+extern struct isis *isis;
+
+static char *csm_statestr[] = 
+{
+  "C_STATE_NA",
+  "C_STATE_INIT",
+  "C_STATE_CONF",
+  "C_STATE_UP"
+};
+
+#define STATE2STR(S) csm_statestr[S]
+
+static char *csm_eventstr[] =
+{
+  "NO_STATE",
+  "ISIS_ENABLE",
+  "IF_UP_FROM_Z",
+  "ISIS_DISABLE",
+  "IF_DOWN_FROM_Z",
+};
+
+#define EVENT2STR(E) csm_eventstr[E]
+
+
+struct isis_circuit*
+isis_csm_state_change (int event, struct isis_circuit *circuit, 
+                       void *arg)
+{
+  int old_state;
+
+  old_state = circuit ? circuit->state : C_STATE_NA;
+  
+  zlog_info ("CSM_EVENT: %s", EVENT2STR(event));
+  
+  switch (old_state) {
+  case C_STATE_NA:
+    if (circuit)
+      zlog_warn ("Non-null circuit while state C_STATE_NA");
+    switch (event) {
+    case ISIS_ENABLE:
+      circuit = isis_circuit_new ();
+      isis_circuit_configure (circuit, (struct isis_area *)arg);
+      circuit->state = C_STATE_CONF;
+      break;
+    case IF_UP_FROM_Z:
+      circuit = isis_circuit_new ();
+      isis_circuit_if_add (circuit, (struct interface *)arg);
+      listnode_add (isis->init_circ_list, circuit);
+      circuit->state = C_STATE_INIT;
+      break;
+    case ISIS_DISABLE:
+      zlog_warn ("circuit already disabled");
+    case IF_DOWN_FROM_Z:
+      zlog_warn ("circuit already disconnected");
+      break;
+    }
+    break;
+  case C_STATE_INIT:
+    switch (event) {
+    case ISIS_ENABLE:
+      isis_circuit_configure (circuit, (struct isis_area *)arg);
+      isis_circuit_up (circuit);
+      circuit->state = C_STATE_UP;
+      isis_event_circuit_state_change (circuit, 1);
+      listnode_delete (isis->init_circ_list, circuit);
+      break;
+    case IF_UP_FROM_Z:
+      zlog_warn ("circuit already connected");
+      break;
+    case ISIS_DISABLE:
+      zlog_warn ("circuit already disabled");
+      break;
+    case IF_DOWN_FROM_Z:
+      isis_circuit_if_del (circuit);
+      listnode_delete (isis->init_circ_list, circuit);
+      isis_circuit_del (circuit);
+      break;
+    }
+    break;
+  case C_STATE_CONF:
+    switch (event) {
+    case ISIS_ENABLE:
+      zlog_warn ("circuit already enabled");
+      break;
+    case IF_UP_FROM_Z:
+      isis_circuit_if_add (circuit, (struct interface *)arg);
+      isis_circuit_up (circuit);
+      circuit->state = C_STATE_UP;
+      isis_event_circuit_state_change (circuit, 1);
+      break;
+    case ISIS_DISABLE:
+      isis_circuit_deconfigure (circuit, (struct isis_area *)arg);
+      isis_circuit_del (circuit);
+      break;
+    case IF_DOWN_FROM_Z:
+      zlog_warn ("circuit already disconnected");
+      break;
+    }
+    break;
+  case C_STATE_UP:
+    switch (event) {
+    case ISIS_ENABLE:
+      zlog_warn ("circuit already configured");
+      break;
+    case IF_UP_FROM_Z:
+      zlog_warn ("circuit already connected");
+      break;
+    case ISIS_DISABLE:
+      isis_circuit_deconfigure (circuit, (struct isis_area *)arg);
+      listnode_add (isis->init_circ_list, circuit);
+      circuit->state = C_STATE_INIT;
+      isis_event_circuit_state_change (circuit, 0);
+      break;
+    case IF_DOWN_FROM_Z:
+      isis_circuit_if_del (circuit);
+      circuit->state = C_STATE_CONF;
+      isis_event_circuit_state_change (circuit, 0);
+      break;
+    }
+    break;
+    
+  default:
+    zlog_warn ("Invalid circuit state %d", old_state);
+  }
+  
+  zlog_info ("CSM_STATE_CHANGE: %s -> %s ", STATE2STR (old_state), 
+             circuit ? STATE2STR (circuit->state) : STATE2STR (C_STATE_NA));
+
+  return circuit;
+}
+
+
+