added ippool.h and ippool.c
diff --git a/examples/ggsn.conf b/examples/ggsn.conf
index c2d3678..5550525 100644
--- a/examples/ggsn.conf
+++ b/examples/ggsn.conf
@@ -36,13 +36,8 @@
 
 # TAG: net
 # IP network address of external packet data network
-# Used to allocate dynamic IP addresses and set up routing.
-#net 192.168.0.0
-
-# TAG: mask
-# IP network mask of external packet data network
-# Used to allocate dynamic IP addresses and set up routing.
-#mask 255.255.255.0
+# Used to set up network interface.
+#net 192.168.0.0/24
 
 # TAG: ipup
 # Script executed after network interface has been brought up.
@@ -54,12 +49,36 @@
 # Executed with the following parameters: <devicename> <ip address>
 #ipdown /etc/ggsn/ip-down
 
+# TAG: dynip
+# Dynamic IP address pool.
+# Used for allocation of dynamic IP address when address is not given
+# by HLR or radius server.
+#dynip 192.168.0.0/24
+
+# TAG: statip
+# Use of this tag is currently UNSUPPORTED
+# Static IP address pool.
+# Used for allocation of static IP address by means of either HLR or
+# radius server.
+#statip 192.168.1.0/24
+
+# TAG: pcodns1
+# Protocol configuration option domain name system server 1.
+#pcodns1 0.0.0.0
+
+# TAG: pcodns2
+# Protocol configuration option domain name system server 2.
+#pcodns2 0.0.0.0
 
 # TAG: timelimit
 # Exit after timelimit seconds.
 # Setting timelimit to zero will cause the program not to exit.
 #timelimit 0
 
+# TAG: apn
+# Use of this tag is EXPERIMENTAL
+# Access point name to connect to when run in client mode.
+#apn internet
 
 # TAG: qos
 # Use of this tag is EXPERIMENTAL
@@ -67,12 +86,6 @@
 # 3 bytes corresponding to ????
 #qos 0x0b921f
 
-# TAG: apn
-# Use of this tag is EXPERIMENTAL
-# Access point name to connect to when run in client mode.
-#apn internet
-
-