diff --git a/parse.c b/parse.c
index 86ddef3fe..1316ccb58 100644
--- a/parse.c
+++ b/parse.c
@@ -305,15 +305,28 @@ int addr_matches(n)
     char *n;
 {
     int i;
-    struct in_addr addr;
+    char *m;
+    struct in_addr addr, mask;
 
-    addr.s_addr = inet_addr(n);
+    /* If there's an explicate netmask, use it. */
+    if ((m = strchr(n, '/'))) {
+	*m++ = '\0';
+	mask.s_addr = inet_addr(m);
+	addr.s_addr = inet_addr(n);
+	*(m - 1) = '/';
 
-    for (i = 0; i < num_interfaces; i++)
-	if (interfaces[i].addr.s_addr == addr.s_addr ||
-	    (interfaces[i].addr.s_addr & interfaces[i].netmask.s_addr)
-	    == addr.s_addr)
-	    return(TRUE);
+	for (i = 0; i < num_interfaces; i++)
+	    if ((interfaces[i].addr.s_addr & mask.s_addr) == addr.s_addr)
+		return(TRUE);
+    } else {
+	addr.s_addr = inet_addr(n);
+
+	for (i = 0; i < num_interfaces; i++)
+	    if (interfaces[i].addr.s_addr == addr.s_addr ||
+		(interfaces[i].addr.s_addr & interfaces[i].netmask.s_addr)
+		== addr.s_addr)
+		return(TRUE);
+    }
 
     return(FALSE);
 }
diff --git a/parse.lex b/parse.lex
index fd113f754..320be5702 100644
--- a/parse.lex
+++ b/parse.lex
@@ -77,6 +77,7 @@ extern void yyerror		__P((char *));
 %}
 
 OCTET			[[:digit:]]{1,3}
+DOTTEDQUAD		{OCTET}(\.{OCTET}){3}
 WORD			[[:alnum:]_-]+
 
 %e	4000
@@ -176,7 +177,7 @@ NOPASSWD:		{
 			    return(USERGROUP);
 			}
 
-{OCTET}(\.{OCTET}){3}	{
+{DOTTEDQUAD}(\/{DOTTEDQUAD})? {
 			    fill(yytext, yyleng);
 			    LEXTRACE("NTWKADDR ");
 			    return(NTWKADDR);