diff --git a/man/dhcpd-pools.1 b/man/dhcpd-pools.1
index 3d7188c..80bb632 100644
--- a/man/dhcpd-pools.1
+++ b/man/dhcpd-pools.1
@@ -129,6 +129,25 @@ Print total summary header
 .PD
 .RE
 .TP
+\fB\-\-warning\fR=\fIpercent\fR
+Turn on alarm output format, and specify percentage number which will
+cause an alarm.  If either a range or shared network will exceed
+warning level return value of the command is
+.BR 1 .
+If critical level is not speficied it defaults to
+.BR 90 .
+The
+.I percent
+argument allows fractions to be used.  Alarm output is intented to be
+used with monitoring, such as Nagios.
+.TP
+\fB\-\-critical\fR=\fIpercent\fR
+The option is similar to warning, with exception of return value which
+is
+.BR 2 .
+If warning level is not specified it defaults to
+.BR 80 .
+.TP
 \fB\-v\fR, \fB\-\-version\fR
 Print version information to standard output and exit successfully.
 .TP
diff --git a/src/defaults.h b/src/defaults.h
index 76e1ec5..6d0a9c5 100644
--- a/src/defaults.h
+++ b/src/defaults.h
@@ -45,4 +45,8 @@ static const unsigned int SHARED_NETWORKS = 8192;
 /* Maximum number of ranges */
 unsigned int RANGES;
 
+/* Alarming defaults */
+#define ALARM_WARN 80
+#define ALARM_CRIT 90
+
 #endif				/* DEFAULTS_H */
diff --git a/src/dhcpd-pools.c b/src/dhcpd-pools.c
index 6488657..7a2313a 100644
--- a/src/dhcpd-pools.c
+++ b/src/dhcpd-pools.c
@@ -52,6 +52,7 @@ extern char *malloc();
 #include <getopt.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <limits.h>
 
 #include "defaults.h"
 #include "dhcpd-pools.h"
@@ -62,6 +63,11 @@ int main(int argc, char **argv)
 	int option_index = 0;
 	char *tmp;
 	struct range_t *tmp_ranges;
+	enum {
+		OPT_WARN = CHAR_MAX + 1,
+		OPT_CRIT
+	};
+	int ret_val;
 
 	/* Options for getopt_long */
 	static struct option const long_options[] = {
@@ -74,6 +80,8 @@ int main(int argc, char **argv)
 		{"limit", required_argument, NULL, 'L'},
 		{"version", no_argument, NULL, 'v'},
 		{"help", no_argument, NULL, 'h'},
+		{"warning", required_argument, NULL, OPT_WARN},
+		{"critical", required_argument, NULL, OPT_CRIT},
 		{NULL, 0, NULL, 0}
 	};
 
@@ -87,6 +95,9 @@ int main(int argc, char **argv)
 	/* Make sure string has zero lenght if there is no
 	 * command line option */
 	config.output_file[0] = '\0';
+	/* Alarming defaults. */
+	config.warning = ALARM_WARN;
+	config.critical = ALARM_CRIT;
 
 	/* File location defaults */
 	strncpy(config.dhcpdconf_file, DHCPDCONF_FILE, MAXLEN - 1);
@@ -160,6 +171,14 @@ int main(int argc, char **argv)
 				}
 			}
 			break;
+		case OPT_WARN:
+			strcpy(config.output_format, "a");
+			config.warning = strtod_or_err(optarg, "illegal argument");
+			break;
+		case OPT_CRIT:
+			strcpy(config.output_format, "a");
+			config.critical = strtod_or_err(optarg, "illegal argument");
+			break;
 		case 'v':
 			/* Print version */
 			print_version();
@@ -178,6 +197,9 @@ int main(int argc, char **argv)
 	case 't':
 		output_analysis = output_txt;
 		break;
+	case 'a':
+		output_analysis = output_alarming;
+		break;
 	case 'h':
 		output_analysis = output_html;
 		break;
@@ -214,10 +236,10 @@ int main(int argc, char **argv)
 		flip_ranges(ranges, tmp_ranges);
 	}
 	free(tmp_ranges);
-	output_analysis();
+	ret_val = output_analysis();
 
 	clean_up();
-	return (EXIT_SUCCESS);
+	return (ret_val);
 }
 
 /* Global allocations, counter resets etc */
diff --git a/src/dhcpd-pools.h b/src/dhcpd-pools.h
index bd4d34f..c9559d1 100644
--- a/src/dhcpd-pools.h
+++ b/src/dhcpd-pools.h
@@ -102,6 +102,8 @@ struct configuration_t {
 	int reverse_order;
 	char *output_file;
 	int output_limit[2];
+	double warning;
+	double critical;
 };
 struct shared_network_t {
 	char *name;
@@ -177,6 +179,7 @@ void *safe_malloc(const size_t size)
 void *safe_realloc(void *__restrict ptr, const size_t size);
 char *safe_strdup(const char *__restrict str) __attribute__ ((nonnull(1)));
 int xstrstr(char *__restrict a, char *__restrict b, int len);
+double strtod_or_err(const char *__restrict str, const char *__restrict errmesg);
 int close_stream(FILE * stream);
 void close_stdout(void);
 void print_version(void) __attribute__ ((noreturn));
@@ -207,6 +210,7 @@ int output_txt(void);
 int output_html(void);
 int output_xml(void);
 int output_csv(void);
+int output_alarming(void);
 /* Memory release, file closing etc */
 void clean_up(void);
 /* Hash functions */
diff --git a/src/other.c b/src/other.c
index f71c55f..5551ce3 100644
--- a/src/other.c
+++ b/src/other.c
@@ -136,6 +136,28 @@ char *safe_strdup(const char *restrict str)
 	return ret;
 }
 
+/* Return percentage value */
+double strtod_or_err(const char *str, const char *errmesg)
+{
+	double num;
+	char *end = NULL;
+
+	if (str == NULL || *str == '\0')
+		goto err;
+	errno = 0;
+	num = strtod(str, &end);
+
+	if (errno || str == end || (end && *end))
+		goto err;
+
+	return num;
+ err:
+	if (errno)
+		err(EXIT_FAILURE, "%s: '%s'", errmesg, str);
+
+	errx(EXIT_FAILURE, "%s: '%s'", errmesg, str);
+}
+
 void flip_ranges(struct range_t *restrict ranges, struct range_t *restrict tmp_ranges)
 {
 	unsigned int i = num_ranges - 1, j;
@@ -237,6 +259,9 @@ This is ISC dhcpd pools usage analyzer.\n\
   -o, --output=FILE      output into a file\n\
   -L, --limit=NR         output limit mask 77 - 00\n");
 	fprintf(out, "\
+      --warning=PERC     set warning alarming limit\n\
+      --critical=PERC    set critical alarming limit\n");
+	fprintf(out, "\
   -v, --version          version information\n\
   -h, --help             this screen\n\
 \n\
diff --git a/src/output.c b/src/output.c
index 7e03bf5..9a4f312 100644
--- a/src/output.c
+++ b/src/output.c
@@ -37,6 +37,7 @@
 
 #include <arpa/inet.h>
 #include <err.h>
+#include <errno.h>
 #include <langinfo.h>
 #include <netinet/in.h>
 #include <stdio.h>
@@ -788,3 +789,87 @@ int output_csv(void)
 	}
 	return 0;
 }
+
+int output_alarming(void)
+{
+	FILE *outfile;
+	struct range_t *range_p;
+	struct shared_network_t *shared_p;
+	int i;
+	float perc;
+	int rw = 0, rc = 0, ro = 0, sw = 0, sc = 0, so = 0;
+	int ret_val, ret;
+
+	range_p = ranges;
+	shared_p = shared_networks;
+
+	if (config.output_file[0]) {
+		outfile = fopen(config.output_file, "w+");
+		if (outfile == NULL) {
+			err(EXIT_FAILURE, "output_alarming: %s",
+			    config.output_file);
+		}
+	} else {
+		outfile = stdout;
+	}
+
+	if (config.output_limit[1] & output_limit_bit_1) {
+		for (i = 0; i < num_ranges; i++) {
+			perc = (float)(100 * range_p->count) /
+			    (range_p->last_ip - range_p->first_ip - 1);
+			if (config.critical < perc)
+				rc++;
+			else if (config.warning < perc)
+				rw++;
+			else
+				ro++;
+			range_p++;
+		}
+	}
+	if (config.output_limit[1] & output_limit_bit_2) {
+		for (i = 0; i < num_shared_networks; i++) {
+			perc = (float)(100 * shared_p->used) /
+			    shared_p->available;
+			if (config.critical < perc)
+				sc++;
+			else if (config.warning < perc)
+				sw++;
+			else
+				so++;
+			shared_p++;
+		}
+	}
+	if (0 < rc || 0 < sc) {
+		ret_val = 2;
+		fprintf(outfile, "CRITICAL: %s: ",
+			program_invocation_short_name);
+	} else if (0 < rw || 0 < sw) {
+		ret_val = 1;
+		fprintf(outfile, "WARNING: %s: ",
+			program_invocation_short_name);
+	} else {
+		ret_val = 0;
+		fprintf(outfile, "OK: ");
+	}
+	if (config.output_limit[0] & output_limit_bit_1) {
+		fprintf(outfile, "Ranges; crit: %d warn: %d ok: %d ", rc, rw,
+			ro);
+	}
+	if (config.output_limit[0] & output_limit_bit_2) {
+		fprintf(outfile, "Shared nets; crit: %d warn: %d ok: %d", sc,
+			sw, so);
+	}
+	fprintf(outfile, "\n");
+	if (outfile == stdout) {
+		ret = fflush(stdout);
+		if (ret) {
+			warn("output_alarming: fflush");
+		}
+	} else {
+		ret = close_stream(outfile);
+		if (ret) {
+			warn("output_alarming: fclose");
+		}
+	}
+	return ret_val;
+}