diff --git a/nhrpd/nhrp_protocol.h b/nhrpd/nhrp_protocol.h
new file mode 100644
index 0000000..a4bc9fa
--- /dev/null
+++ b/nhrpd/nhrp_protocol.h
@@ -0,0 +1,128 @@
+/* nhrp_protocol.h - NHRP protocol definitions
+ *
+ * Copyright (c) 2007-2012 Timo Teräs <timo.teras@iki.fi>
+ *
+ * This software is licensed under the MIT License.
+ * See MIT-LICENSE.txt for additional details.
+ */
+
+#ifndef NHRP_PROTOCOL_H
+#define NHRP_PROTOCOL_H
+
+#include <stdint.h>
+
+/* NHRP Ethernet protocol number */
+#define ETH_P_NHRP				0x2001
+
+/* NHRP Version */
+#define NHRP_VERSION_RFC2332			1
+
+/* NHRP Packet Types */
+#define NHRP_PACKET_RESOLUTION_REQUEST		1
+#define NHRP_PACKET_RESOLUTION_REPLY		2
+#define NHRP_PACKET_REGISTRATION_REQUEST	3
+#define NHRP_PACKET_REGISTRATION_REPLY		4
+#define NHRP_PACKET_PURGE_REQUEST		5
+#define NHRP_PACKET_PURGE_REPLY			6
+#define NHRP_PACKET_ERROR_INDICATION		7
+#define NHRP_PACKET_TRAFFIC_INDICATION		8
+
+/* NHRP Extension Types */
+#define NHRP_EXTENSION_FLAG_COMPULSORY		0x8000
+#define NHRP_EXTENSION_END			0
+#define NHRP_EXTENSION_PAYLOAD			0
+#define NHRP_EXTENSION_RESPONDER_ADDRESS	3
+#define NHRP_EXTENSION_FORWARD_TRANSIT_NHS	4
+#define NHRP_EXTENSION_REVERSE_TRANSIT_NHS	5
+#define NHRP_EXTENSION_AUTHENTICATION		7
+#define NHRP_EXTENSION_VENDOR			8
+#define NHRP_EXTENSION_NAT_ADDRESS		9
+
+/* NHRP Error Indication Codes */
+#define NHRP_ERROR_UNRECOGNIZED_EXTENSION	1
+#define NHRP_ERROR_LOOP_DETECTED		2
+#define NHRP_ERROR_PROTOCOL_ADDRESS_UNREACHABLE	6
+#define NHRP_ERROR_PROTOCOL_ERROR		7
+#define NHRP_ERROR_SDU_SIZE_EXCEEDED		8
+#define NHRP_ERROR_INVALID_EXTENSION		9
+#define NHRP_ERROR_INVALID_RESOLUTION_REPLY	10
+#define NHRP_ERROR_AUTHENTICATION_FAILURE	11
+#define NHRP_ERROR_HOP_COUNT_EXCEEDED		15
+
+/* NHRP CIE Codes */
+#define NHRP_CODE_SUCCESS			0
+#define NHRP_CODE_ADMINISTRATIVELY_PROHIBITED	4
+#define NHRP_CODE_INSUFFICIENT_RESOURCES	5
+#define NHRP_CODE_NO_BINDING_EXISTS		11
+#define NHRP_CODE_BINDING_NON_UNIQUE		13
+#define NHRP_CODE_UNIQUE_ADDRESS_REGISTERED     14
+
+/* NHRP Flags for Resolution request/reply */
+#define NHRP_FLAG_RESOLUTION_SOURCE_IS_ROUTER	0x8000
+#define NHRP_FLAG_RESOLUTION_AUTHORATIVE	0x4000
+#define NHRP_FLAG_RESOLUTION_DESTINATION_STABLE	0x2000
+#define NHRP_FLAG_RESOLUTION_UNIQUE		0x1000
+#define NHRP_FLAG_RESOLUTION_SOURCE_STABLE	0x0800
+#define NHRP_FLAG_RESOLUTION_NAT		0x0002
+
+/* NHRP Flags for Registration request/reply */
+#define NHRP_FLAG_REGISTRATION_UNIQUE		0x8000
+#define NHRP_FLAG_REGISTRATION_NAT		0x0002
+
+/* NHRP Flags for Purge request/reply */
+#define NHRP_FLAG_PURGE_NO_REPLY		0x8000
+
+/* NHRP Authentication extension types (ala Cisco) */
+#define NHRP_AUTHENTICATION_PLAINTEXT		0x00000001
+
+/* NHRP Packet Structures */
+struct nhrp_packet_header {
+	/* Fixed header */
+	uint16_t	afnum;
+	uint16_t	protocol_type;
+	uint8_t		snap[5];
+	uint8_t		hop_count;
+	uint16_t	packet_size;
+	uint16_t	checksum;
+	uint16_t	extension_offset;
+	uint8_t		version;
+	uint8_t		type;
+	uint8_t		src_nbma_address_len;
+	uint8_t		src_nbma_subaddress_len;
+
+	/* Mandatory header */
+	uint8_t		src_protocol_address_len;
+	uint8_t		dst_protocol_address_len;
+	uint16_t	flags;
+	union {
+		uint32_t		request_id;
+		struct {
+			uint16_t	code;
+			uint16_t	offset;
+		} error;
+	} u;
+} __attribute__((packed));
+
+struct nhrp_cie_header {
+	uint8_t		code;
+	uint8_t		prefix_length;
+	uint16_t	unused;
+	uint16_t	mtu;
+	uint16_t	holding_time;
+	uint8_t		nbma_address_len;
+	uint8_t		nbma_subaddress_len;
+	uint8_t		protocol_address_len;
+	uint8_t		preference;
+} __attribute__((packed));
+
+struct nhrp_extension_header {
+	uint16_t	type;
+	uint16_t	length;
+} __attribute__((packed));
+
+struct nhrp_cisco_authentication_extension {
+	uint32_t	type;
+	uint8_t		secret[8];
+} __attribute__((packed));
+
+#endif