diff -ur cdp-tools.orig/cdp-send.c cdp-tools/cdp-send.c
--- cdp-tools.orig/cdp-send.c	2006-10-26 14:04:33.000000000 -0400
+++ cdp-tools/cdp-send.c	2007-02-28 17:13:35.000000000 -0500
@@ -2,6 +2,8 @@
  *     cdp-send is part of cdp-tools.
  *     cdp-tools is (c) 2003-2006 Internet Connection, Inc.
  *
+ *     Voice VLAN support by Kristian Kielhofner <kris@krisk.org>
+ * 
  *     cdp-send is free software; you can redistribute it and/or modify
  *     it under the terms of the GNU General Public License as published by
  *     the Free Software Foundation; either version 2, or (at your option)
@@ -37,6 +39,8 @@
 
 static unsigned int use_vlanid = 0;
 
+static unsigned int use_voiceid = 0;
+
 static unsigned char *use_ip_prefix = 0;
 static unsigned int use_ip_prefix_len = 0;
 
@@ -178,7 +182,7 @@
 
 	buffer+=sizeof(struct cdp_header);
 
-	buffer[0]=0x1; /* cdp version */
+	buffer[0]=0x2; /* cdp version */
 	buffer[1]=0xb4; /* cdp holdtime, 180 sec by default */
 	buffer[2]=buffer[3]=0; /* checksum - will calculate later */
 
@@ -299,7 +303,7 @@
 	if (duplex == 0) return 0;
 	if (len < 5) return 0;
 	sx_write_short(buffer,htons(0x000b)); /* type=port duplex */
-	sx_write_short(buffer+2,htons(1));
+	sx_write_short(buffer+2,htons(5)); /* totallength*/
 	buffer[4] = (duplex == 1 ? 1 : 0);
 	return 5;
 }
@@ -309,11 +313,23 @@
 {
 	if (len < 6) return 0;
 	sx_write_short(buffer,htons(0x000a)); /* type=vlan id */
-	sx_write_short(buffer+2,htons(2));
+	sx_write_short(buffer+2,htons(6)); /* totallength*/
 	sx_write_short(buffer+4,htons(use_vlanid));
 	return 6;
 }
 
+int
+cdp_add_voiceid(unsigned char* buffer, int len)
+{
+	if (len < 7) return 0;
+	sx_write_short(buffer,htons(0x000e)); /* type=voice vlan id */
+	sx_write_short(buffer+2,htons(7)); /* totallength*/
+	sx_write_short(buffer+4,htons(0x1)); /*PAD*/
+	sx_write_short(buffer+5,htons(use_voiceid));
+	return 7;
+}
+
+
 
 unsigned short
 cdp_checksum(unsigned char *ptr, int length) {
@@ -346,6 +362,7 @@
 "  -d         enable debugging output\n"
 "  -D dom     specify VTP management domain (octal escapes ok)\n"
 "  -L vlan    specify native VLAN (vlanid)\n"
+"  -V vlan    specify voice VLAN (voiceid)\n"
 "  -m mach    specify machine/platform to advertise (e.g. \"%s\")\n"
 "  -n name    specify a hostname\n"
 "  -p name    override port name (default: interface)\n"
@@ -435,11 +452,12 @@
 	struct cdp_interface *ifaces=NULL;
 	int specify_duplex = 0;
 	int specified_vlan = 0;
+	int specified_vvlan = 0;
 	int didcap = 0;
 	char *q;
 
 	uname(&myuname);
-	while((c=getopt(argc,argv,"a:c:dD:L:m:n:op:P:s:S:t:"))!=EOF) { 
+	while((c=getopt(argc,argv,"a:c:dD:L:V:m:n:op:P:s:S:t:"))!=EOF) { 
 		switch(c) { 
 		case 'a':
 			if (inet_aton(optarg, &iaddr)) {
@@ -518,6 +536,15 @@
 			specified_vlan=1;
 			use_vlanid = i;
 			break;
+		case 'V':
+			i = strtod(optarg, &q);
+			if ((q && *q) || i < 0 || i > 65535) {
+				fprintf(stderr, "Voice VLAN ID is an unsigned 16-bit integer\n");
+				exit(1);
+			}
+			specified_vvlan=1;
+			use_voiceid = i;
+			break;
 		case 'm':
 			use_machine = strdup(optarg);
 			if (!use_machine) {
@@ -673,7 +700,11 @@
 			if (specified_vlan) {
 				offset+=cdp_add_vlanid(buffer+offset, sizeof(buffer)-offset);
 			}
-	
+
+			if (specified_vvlan) {
+				offset+=cdp_add_voiceid(buffer+offset, sizeof(buffer)-offset);
+			}
+			
 			((struct cdp_header*)buffer)->length=htons(offset-14);
 		
 			*(u_short*)(buffer+sizeof(struct cdp_header)+2)=cdp_checksum(