diff --git a/tools/firmware-utils/Makefile b/tools/firmware-utils/Makefile
index 28f8f0555a55..cec8398a27d5 100644
--- a/tools/firmware-utils/Makefile
+++ b/tools/firmware-utils/Makefile
@@ -97,6 +97,7 @@ define Host/Compile
 	$(call cc,wrt400n cyg_crc32)
 	$(call cc,xorimage)
 	$(call cc,zyimage,-Wall)
+	$(call cc,zytrx,-Wall)
 	$(call cc,zyxbcm)
 endef
 
diff --git a/tools/firmware-utils/src/zytrx.c b/tools/firmware-utils/src/zytrx.c
new file mode 100644
index 000000000000..302efc601065
--- /dev/null
+++ b/tools/firmware-utils/src/zytrx.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * zytrx - add header to images for ZyXEL NR7101
+ *
+ * Based on add_header.c - partially based on OpenWrt's
+ * motorola-bin.c
+ *
+ * Copyright (C) 2008 Imre Kaloz  <kaloz@openwrt.org>
+ *                    Gabor Juhos <juhosg@openwrt.org>
+ * Copyright (C) 2021 Bjørn Mork <bjorn@mork.no>
+
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License,
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <netinet/in.h>
+#include <inttypes.h>
+
+#define BPB 8 /* bits/byte */
+
+static uint32_t crc32[1<<BPB];
+
+static void init_crc32(void)
+{
+	const uint32_t poly = ntohl(0x2083b8ed);
+	int n;
+
+	for (n = 0; n < 1<<BPB; n++) {
+		uint32_t crc = n;
+		int bit;
+
+		for (bit = 0; bit < BPB; bit++)
+			crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
+		crc32[n] = crc;
+	}
+}
+
+static uint32_t crc32buf(const unsigned char *buf, size_t len)
+{
+	uint32_t crc = 0xFFFFFFFF;
+
+	for (; len; len--, buf++)
+		crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
+	return ~crc;
+}
+
+/* HDR0 reversed, to be stored as BE */
+#define MAGIC		0x30524448  /* HDR0 reversed, to be stored as BE */
+
+/* All numbers are stored as BE */
+struct zytrx_t {
+	uint32_t magic;
+	uint32_t len_h;		/* Length of this header */
+	uint32_t len_t;		/* Total length of file  */
+	uint32_t crc32_p;	/* Bit inverted 32-bit CRC of image payload */
+	uint8_t  verInt[32];	/* String "5.0.0.0\n" zero padded */
+	uint8_t  verExt[32];	/* String "\n" zero padded */
+	uint32_t len_p;		/* Length of image payload */
+	uint8_t  pad1[12];	/* zero padding(?) */
+	uint8_t  code[164];	/* string "3 6035 122 0\n" zero padded */
+	uint8_t  chipid[8];	/* string "MT7621A" zero padded */
+	uint8_t  boardid[16];	/* string "NR7101" zero padded */
+	uint32_t modelid;	/* modelid as 4 BCD digits: 0x07010001 */
+	uint8_t  pad2[8];	/* zero padding(?) */
+	uint8_t  swVersionInt[32];	/* ZyXEL version string: "1.00(ABUV.0)D0" zero padded */
+	uint8_t  swVersionExt[32];	/* identical to swVersionInt  */
+	uint8_t  pad4[4];	/* zero padding(?) */
+	uint32_t kernelChksum;	/* no idea how this is computed - reported but not validated */
+	uint8_t  pad5[4];	/* zero padding(?) */
+	uint32_t crc32_h;	/* Bit inverted 32-bit CRC of this header payload */
+	uint8_t  pad6[4];	/* zero padding(?) */
+};
+
+/* static?() field values of unknown meaning - maybe ove to board
+ * table when we know the significance
+ */
+#define VER_INT		"5.0.0.0\n"
+#define VER_EXT		"\n"
+#define CODE		"3 6035 122 0\n"
+#define KERNELCHKSUM	0x12345678
+
+/* table of supported devices using this header format */
+static struct board_t {
+	uint8_t  chipid[8];
+	uint8_t  boardid[16];
+	uint32_t modelid;
+} boards[] = {
+	{ "MT7621A", "NR7101", 0x07010001 },
+	{}
+};
+
+static int find_board(struct zytrx_t *h, char *board)
+{
+	struct board_t *p;
+
+	for (p = boards; p->modelid; p++) {
+		if (strncmp((const char *)p->boardid, board, sizeof(p->boardid)))
+			continue;
+		memcpy(h->chipid, p->chipid, sizeof(h->chipid));
+		memcpy(h->boardid, p->boardid, sizeof(h->boardid));
+		h->modelid = htonl(p->modelid);
+		return 0;
+	}
+	return -1;
+}
+
+static void usage(const char *name)
+{
+	struct board_t *p;
+
+	fprintf(stderr, "Usage:\n");
+	fprintf(stderr, " %s -B <board> -v <versionstr> -i <file> [-o <outputfile>]\n\n", name);
+	fprintf(stderr, "Supported <board> values:\n");
+	for (p = boards; p->modelid; p++)
+		fprintf(stderr, "\t%-12s\n", p->boardid);
+	fprintf(stderr, "\nExample:\n");
+	fprintf(stderr, " %s -B %s -v foobar-1.0 -i my.img -o out.img\n\n", name,
+		boards[0].boardid);
+	exit(EXIT_FAILURE);
+}
+
+static void errexit(const char *msg)
+{
+	fprintf(stderr, "ERR: %s: %s\n", msg, errno ? strerror(errno) : "unknown");
+	exit(EXIT_FAILURE);
+}
+
+static void *map_input(const char *name, size_t *len)
+{
+	struct stat stat;
+	void *mapped;
+	int fd;
+
+	fd = open(name, O_RDONLY);
+	if (fd < 0)
+		return NULL;
+	if (fstat(fd, &stat) < 0) {
+		close(fd);
+		return NULL;
+	}
+	*len = stat.st_size;
+	mapped = mmap(NULL, stat.st_size, PROT_READ, MAP_SHARED, fd, 0);
+	if (close(fd) < 0)
+		return NULL;
+	return mapped;
+}
+
+int main(int argc, char **argv)
+{
+	int c, fdout = STDOUT_FILENO;
+	void *input_file = NULL;
+	size_t file_len, len;
+	uint32_t crc;
+	struct zytrx_t h = {
+		.magic		= htonl(MAGIC),
+		.len_h		= htonl(sizeof(h)),
+		.verInt		= VER_INT,
+		.verExt		= VER_EXT,
+		.code		= CODE,
+		.kernelChksum	= htonl(KERNELCHKSUM),
+	};
+
+	while ((c = getopt(argc, argv, "B:v:i:o:")) != -1) {
+		switch (c) {
+		case 'B':
+			if (find_board(&h, optarg) < 0)
+				errexit("unsupported board");
+			break;
+		case 'v':
+			len = strlen(optarg);
+			if (len > sizeof(h.swVersionInt))
+				errexit("version string too long");
+			memcpy(h.swVersionInt, optarg, len);
+			memcpy(h.swVersionExt, optarg, len);
+			break;
+		case 'i':
+			input_file = map_input(optarg, &file_len);
+			if (!input_file)
+				errexit(optarg);
+			break;
+		case 'o':
+			fdout = open(optarg, O_WRONLY | O_CREAT, 0644);
+			if (fdout < 0)
+				errexit(optarg);
+			break;
+		default:
+			usage(argv[0]);
+		}
+	}
+
+	/* required paremeters */
+	if (!input_file || !h.modelid || !h.swVersionInt[0])
+		usage(argv[0]);
+
+	/* length fields */
+	h.len_t = htonl(sizeof(h) + file_len);
+	h.len_p = htonl(file_len);
+
+	/* crc fields */
+	init_crc32();
+	crc = crc32buf(input_file, file_len);
+	h.crc32_p = htonl(~crc);
+	crc = crc32buf((unsigned char *)&h, sizeof(h));
+	h.crc32_h = htonl(~crc);
+
+	/* dump new image */
+	write(fdout, &h, sizeof(h));
+	write(fdout, input_file, file_len);
+
+	/* close files */
+	munmap(input_file, file_len);
+	if (fdout != STDOUT_FILENO)
+		close(fdout);
+
+	return EXIT_SUCCESS;
+}
