diff --git a/lib/ChangeLog b/lib/ChangeLog
index 567f603..8aaf382 100644
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,5 +1,31 @@
 2005-04-02 Andrew J. Schorr <ajschorr@alumni.princeton.edu>
 
+	* if.h: Remove define for IFINDEX_INTERNBASE and add define
+	  IFINDEX_INTERNAL 0, since all internal (i.e. non-kernel) pseudo-
+	  interfaces should have ifindex set to 0.
+	  (if_new) Remove function.
+	  (if_delete_retain) New function to delete an interface without
+	  removing from iflist and freeing the structure.
+	  (ifname2ifindex) New function.
+	* if.c: (if_new) Remove function (absorb into if_create).
+	  (if_create) Replace function if_new with call to calloc.
+	  Set ifp->ifindex to IFINDEX_INTERNAL.  Fix off-by-one error
+	  in assert to check length of interface name.  Add error message
+	  if interface with this name already exists.
+	  (if_delete_retain) New function to delete an interface without
+	  removing from iflist and freeing the structure.
+	  (if_delete) Implement with help of if_delete_retain.
+	  (ifindex2ifname) Reimplement using if_lookup_by_index.
+	  (ifname2ifindex) New function to complement ifindex2ifname.
+	  (interface) The interface command should check the name length
+	  and fail with a warning message if it is too long.
+	  (no_interface) Fix spelling in warning message.
+	  (if_nametoindex) Reimplement using if_lookup_by_name.
+	  (if_indextoname, ifaddr_ipv4_lookup) Reimplement using
+	  if_lookup_by_index.
+
+2005-04-02 Andrew J. Schorr <ajschorr@alumni.princeton.edu>
+
 	* zebra.h: Should include str.h to pick up missing functions.
 	* str.h: Declare strnlen if needed.
 	* str.c: Do not include str.h since zebra.h now includes it.
diff --git a/lib/if.c b/lib/if.c
index 7385ff6..e35e3ed 100644
--- a/lib/if.c
+++ b/lib/if.c
@@ -113,28 +113,22 @@
 
 /* Create new interface structure. */
 struct interface *
-if_new ()
-{
-  struct interface *ifp;
-
-  ifp = XMALLOC (MTYPE_IF, sizeof (struct interface));
-  memset (ifp, 0, sizeof (struct interface));
-  return ifp;
-}
-
-struct interface *
 if_create (const char *name, int namelen)
 {
   struct interface *ifp;
 
-  ifp = if_new ();
+  ifp = XCALLOC (MTYPE_IF, sizeof (struct interface));
+  ifp->ifindex = IFINDEX_INTERNAL;
   
   assert (name);
-  assert (namelen <= (INTERFACE_NAMSIZ + 1));
+  assert (namelen <= INTERFACE_NAMSIZ);	/* Need space for '\0' at end. */
   strncpy (ifp->name, name, namelen);
-  ifp->name[INTERFACE_NAMSIZ] = '\0';
+  ifp->name[namelen] = '\0';
   if (if_lookup_by_name(ifp->name) == NULL)
     listnode_add_sort (iflist, ifp);
+  else
+    zlog_err("if_create(%s): corruption detected -- interface with this "
+	     "name exists already!", ifp->name);
   ifp->connected = list_new ();
   ifp->connected->del = (void (*) (void *)) connected_free;
 
@@ -144,17 +138,24 @@
   return ifp;
 }
 
+/* Delete interface structure. */
+void
+if_delete_retain (struct interface *ifp)
+{
+  if (if_master.if_delete_hook)
+    (*if_master.if_delete_hook) (ifp);
+
+  /* Free connected address list */
+  list_delete (ifp->connected);
+}
+
 /* Delete and free interface structure. */
 void
 if_delete (struct interface *ifp)
 {
   listnode_delete (iflist, ifp);
 
-  if (if_master.if_delete_hook)
-    (*if_master.if_delete_hook) (ifp);
-
-  /* Free connected address list */
-  list_delete (ifp->connected);
+  if_delete_retain(ifp);
 
   XFREE (MTYPE_IF, ifp);
 }
@@ -194,16 +195,18 @@
 char *
 ifindex2ifname (unsigned int index)
 {
-  struct listnode *node;
   struct interface *ifp;
 
-  for (node = listhead (iflist); node; nextnode (node))
-    {
-      ifp = getdata (node);
-      if (ifp->ifindex == index)
-	return ifp->name;
-    }
-  return (char *) "unknown";
+  return ((ifp = if_lookup_by_index(index)) != NULL) ?
+  	 ifp->name : (char *)"unknown";
+}
+
+unsigned int
+ifname2ifindex (const char *name)
+{
+  struct interface *ifp;
+
+  return ((ifp = if_lookup_by_name(name)) != NULL) ? ifp->ifindex : 0;
 }
 
 /* Interface existance check by interface name. */
@@ -491,11 +494,20 @@
        "Interface's name\n")
 {
   struct interface *ifp;
+  size_t sl;
+
+  if ((sl = strlen(argv[0])) > INTERFACE_NAMSIZ)
+    {
+      vty_out (vty, "%% Interface name %s is invalid: length exceeds "
+		    "%d characters%s",
+	       argv[0], INTERFACE_NAMSIZ, VTY_NEWLINE);
+      return CMD_WARNING;
+    }
 
   ifp = if_lookup_by_name (argv[0]);
 
   if (ifp == NULL)
-    ifp = if_create (argv[0], INTERFACE_NAMSIZ);
+    ifp = if_create (argv[0], sl);
   vty->index = ifp;
   vty->node = INTERFACE_NODE;
 
@@ -515,17 +527,17 @@
   ifp = if_lookup_by_name (argv[0]);
 
   if (ifp == NULL)
-  {
-    vty_out (vty, "%% Inteface %s does not exist%s", argv[0], VTY_NEWLINE);
-    return CMD_WARNING;
-  }
+    {
+      vty_out (vty, "%% Interface %s does not exist%s", argv[0], VTY_NEWLINE);
+      return CMD_WARNING;
+    }
 
   if (CHECK_FLAG (ifp->status, ZEBRA_INTERFACE_ACTIVE)) 
-  {
-    vty_out (vty, "%% Only inactive interfaces can be deleted%s",
-            VTY_NEWLINE);
-    return CMD_WARNING;
-  }
+    {
+      vty_out (vty, "%% Only inactive interfaces can be deleted%s",
+	      VTY_NEWLINE);
+      return CMD_WARNING;
+    }
 
   if_delete(ifp);
 
@@ -726,16 +738,9 @@
 unsigned int
 if_nametoindex (const char *name)
 {
-  struct listnode *node;
   struct interface *ifp;
 
-  for (node = listhead (iflist); node; nextnode (node))
-    {
-      ifp = getdata (node);
-      if (strcmp (ifp->name, name) == 0)
-	return ifp->ifindex;
-    }
-  return 0;
+  return ((ifp = if_lookup_by_name(name)) != NULL) ? ifp->ifindex : 0;
 }
 #endif
 
@@ -743,19 +748,12 @@
 char *
 if_indextoname (unsigned int ifindex, char *name)
 {
-  struct listnode *node;
   struct interface *ifp;
 
-  for (node = listhead (iflist); node; nextnode (node))
-    {
-      ifp = getdata (node);
-      if (ifp->ifindex == ifindex)
-	{
-	  memcpy (name, ifp->name, IFNAMSIZ);
-	  return ifp->name;
-	}
-    }
-  return NULL;
+  if (!(ifp = if_lookup_by_index(ifindex)))
+    return NULL;
+  strncpy (name, ifp->name, IFNAMSIZ);
+  return ifp->name;
 }
 #endif
 
@@ -832,16 +830,7 @@
       return ifp;
     }
   else
-    {
-      for (node = listhead (iflist); node; nextnode (node))
-	{
-	  ifp = getdata (node);
-
-	  if (ifp->ifindex == ifindex)
-	    return ifp;
-	}
-    }
-  return NULL;
+    return if_lookup_by_index(ifindex);
 }
 
 /* Initialize interface list. */
diff --git a/lib/if.h b/lib/if.h
index f5efda6..df9ff60 100644
--- a/lib/if.h
+++ b/lib/if.h
@@ -36,10 +36,6 @@
 #define INTERFACE_NAMSIZ      20
 #define INTERFACE_HWADDR_MAX  20
 
-/* Internal If indexes start at 0xFFFFFFFF and go down to 1 greater
-   than this */
-#define IFINDEX_INTERNBASE 0x80000000
-
 #ifdef HAVE_PROC_NET_DEV
 struct if_stats
 {
@@ -75,11 +71,19 @@
 /* Interface structure */
 struct interface 
 {
-  /* Interface name. */
+  /* Interface name.  This should probably never be changed after the
+     interface is created, because the configuration info for this interface
+     is associated with this structure.  For that reason, the interface
+     should also never be deleted (to avoid losing configuration info).
+     To delete, just set ifindex to IFINDEX_INTERNAL to indicate that the
+     interface does not exist in the kernel.
+   */
   char name[INTERFACE_NAMSIZ + 1];
 
-  /* Interface index. */
+  /* Interface index (should be IFINDEX_INTERNAL for non-kernel or
+     deleted interfaces). */
   unsigned int ifindex;
+#define IFINDEX_INTERNAL	0
 
   /* Zebra internal interface status */
   u_char status;
@@ -208,14 +212,22 @@
 
 /* Prototypes. */
 int if_cmp_func (struct interface *, struct interface *);
-struct interface *if_new (void);
 struct interface *if_create (const char *name, int namelen);
 struct interface *if_lookup_by_index (unsigned int);
 struct interface *if_lookup_by_name (const char *);
 struct interface *if_lookup_exact_address (struct in_addr);
 struct interface *if_lookup_address (struct in_addr);
 struct interface *if_get_by_name (const char *);
-void if_delete (struct interface *);
+
+/* Delete the interface, but do not free the structure, and leave it in the
+   interface list.  It is often advisable to leave the pseudo interface 
+   structure because there may be configuration information attached. */
+extern void if_delete_retain (struct interface *);
+
+/* Delete and free the interface structure: calls if_delete_retain and then
+   deletes it from the interface list and frees the structure. */
+extern void if_delete (struct interface *);
+
 int if_is_up (struct interface *);
 int if_is_running (struct interface *);
 int if_is_operative (struct interface *);
@@ -226,9 +238,18 @@
 void if_add_hook (int, int (*)(struct interface *));
 void if_init ();
 void if_dump_all ();
-char *ifindex2ifname (unsigned int);
 extern const char *if_flag_dump(unsigned long);
 
+/* Please use ifindex2ifname instead of if_indextoname where possible;
+   ifindex2ifname uses internal interface info, whereas if_indextoname must
+   make a system call. */
+extern char *ifindex2ifname (unsigned int);
+
+/* Please use ifname2ifindex instead of if_nametoindex where possible;
+   ifname2ifindex uses internal interface info, whereas if_nametoindex must
+   make a system call. */
+extern unsigned int ifname2ifindex(const char *ifname);
+
 /* Connected address functions. */
 struct connected *connected_new ();
 void connected_free (struct connected *);