diff -up tcpdump-3.9.8/addrtoname.c.portnumbers tcpdump-3.9.8/addrtoname.c

--- tcpdump-3.9.8/addrtoname.c.portnumbers	2007-09-26 03:59:52.000000000 +0200

+++ tcpdump-3.9.8/addrtoname.c	2008-08-29 13:53:12.000000000 +0200

@@ -704,7 +704,7 @@ init_servarray(void)

 		while (table->name)

 			table = table->nxt;

-		if (nflag) {

+		if (nflag > 1) {

 			(void)snprintf(buf, sizeof(buf), "%d", port);

 			table->name = strdup(buf);

 		} else

@@ -1104,7 +1104,7 @@ init_addrtoname(u_int32_t localnet, u_in

 		f_localnet = localnet;

 		f_netmask = mask;

 	}

-	if (nflag)

+	if (nflag > 1)

 		/*

 		 * Simplest way to suppress names.

 		 */

diff -up tcpdump-3.9.8/tcpdump.1.portnumbers tcpdump-3.9.8/tcpdump.1

--- tcpdump-3.9.8/tcpdump.1.portnumbers	2008-08-29 13:53:12.000000000 +0200

+++ tcpdump-3.9.8/tcpdump.1	2008-08-29 13:53:12.000000000 +0200

@@ -403,7 +403,11 @@ Use \fIsecret\fP as a shared secret for 

 TCP segments with the TCP-MD5 option (RFC 2385), if present.

 .TP

 .B \-n

-Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.

+Don't convert host addresses to names.  This can be used to avoid 

+DNS lookups.

+.TP

+.B \-nn

+Don't convert protocol and port numbers etc. to names either.  

 .TP

 .B \-N

 Don't print domain name qualification of host names.