Index: arpwatch/arpwatch.8
diff -u arpwatch/arpwatch.8:1.1.1.1.2.2 arpwatch/arpwatch.8:1.1.1.1.24.2
--- arpwatch/arpwatch.8:1.1.1.1.2.2	Thu Aug 12 22:31:09 2004
+++ arpwatch/arpwatch.8	Thu Aug 12 23:44:44 2004
@@ -63,6 +63,14 @@
 ]
 .\" **
 .\" **
+.br
+.ti +8
+[
+.B -z
+.I ignorenet/ignoremask
+]
+.\" **
+.\" **
 .ad
 .SH DESCRIPTION
 .B Arpwatch
@@ -127,6 +135,13 @@
 .\" **
 .\" **
 .LP
+(Debian) The
+.B -z
+flag is used to set a range of ip addresses to ignore (such as a DHCP
+range). Netmask is specified as 255.255.128.0.
+.\" **
+.\" **
+.LP
 Note that an empty
 .I arp.dat
 file must be created before the first time you run
Index: arpwatch/arpwatch.c
diff -u arpwatch/arpwatch.c:1.1.1.1.2.5 arpwatch/arpwatch.c:1.1.1.1.2.1.14.6
--- arpwatch/arpwatch.c:1.1.1.1.2.5	Sat Aug 14 02:33:07 2004
+++ arpwatch/arpwatch.c	Fri Aug 13 02:40:20 2004
@@ -123,6 +123,9 @@
 static int nets_ind;
 static int nets_size;
 
+static struct in_addr ignore_net;
+static struct in_addr ignore_netmask;
+
 extern int optind;
 extern int opterr;
 extern char *optarg;
@@ -172,7 +175,11 @@
 		"r:"
 		/**/
 		/**/
+		"z:"
+		/**/
+		/**/
 	;
+	char *tmpptr;
 
 	if (argv[0] == NULL)
 		prog = "arpwatch";
@@ -190,6 +197,9 @@
 	interface = NULL;
 	rfilename = NULL;
 	pd = NULL;
+
+	inet_aton("0.0.0.0", &ignore_netmask);
+	inet_aton("255.255.255.255", &ignore_netmask);
 	while ((op = getopt(argc, argv, options)) != EOF)
 		switch (op) {
 
@@ -223,6 +233,14 @@
 			break;
 		/**/
 		/**/
+		case 'z':
+			tmpptr = strtok(optarg, "/");
+			inet_aton(tmpptr, &ignore_net);
+			tmpptr = strtok(NULL, "/");
+			inet_aton(tmpptr, &ignore_netmask);
+			break;
+		/**/
+		/**/
 		default:
 			usage();
 		}
@@ -418,7 +436,15 @@
 		return;
 	}
 
+	/* Ignores the specified netmask/metwork */
+	if ((sia & ignore_netmask.s_addr) == ignore_net.s_addr) {
+		if (debug) {
+			dosyslog(LOG_INFO, "ignored", sia, sea, sha, interface);
+		}
+		return;
+	}
 	/* Got a live one */
+
 	t = h->ts.tv_sec;
 	can_checkpoint = 0;
 	if (!ent_add(sia, sea, t, NULL))
@@ -785,6 +811,9 @@
 		"[-r file] "
 		/**/
 		/**/
+		"[-z ignorenet/ignoremask] "
+		/**/
+		/**/
 		"\n"
 	;