diff --git a/sys/netinet6/icmp6.c b/sys/netinet6/icmp6.c
index 7c177c49583e..cb7d3131c6d3 100644
--- a/sys/netinet6/icmp6.c
+++ b/sys/netinet6/icmp6.c
@@ -373,7 +373,7 @@ icmp6_error(m, type, code, param)
 
 	/*
 	 * icmp6_reflect() is designed to be in the input path.
-	 * icmp6_error() can be called from both input and outut path,
+	 * icmp6_error() can be called from both input and output path,
 	 * and if we are in output path rcvif could contain bogus value.
 	 * clear m->m_pkthdr.rcvif for safety, we should have enough scope
 	 * information in ip header (nip6).
@@ -387,7 +387,7 @@ icmp6_error(m, type, code, param)
 
   freeit:
 	/*
-	 * If we can't tell wheter or not we can generate ICMP6, free it.
+	 * If we can't tell whether or not we can generate ICMP6, free it.
 	 */
 	m_freem(m);
 }
@@ -448,7 +448,7 @@ icmp6_input(mp, offp, proto)
 	if (faithprefix_p != NULL && (*faithprefix_p)(&ip6->ip6_dst)) {
 		/*
 		 * Deliver very specific ICMP6 type only.
-		 * This is important to deilver TOOBIG.  Otherwise PMTUD
+		 * This is important to deliver TOOBIG.  Otherwise PMTUD
 		 * will not work.
 		 */
 		switch (icmp6->icmp6_type) {
diff --git a/sys/netinet6/in6_src.c b/sys/netinet6/in6_src.c
index 9d429d3ad6ad..0f522b3113ab 100644
--- a/sys/netinet6/in6_src.c
+++ b/sys/netinet6/in6_src.c
@@ -461,7 +461,7 @@ selectroute(dstsock, opts, mopts, ro, retifp, retrt, clone, norouteok)
 		    (norouteok || retrt == NULL ||
 		    IN6_IS_ADDR_MULTICAST(dst))) {
 			/*
-			 * we do not have to check nor get the route for
+			 * we do not have to check or get the route for
 			 * multicast.
 			 */
 			goto done;
diff --git a/sys/netinet6/in6_var.h b/sys/netinet6/in6_var.h
index f9431f8e77f2..34f52fde88ea 100644
--- a/sys/netinet6/in6_var.h
+++ b/sys/netinet6/in6_var.h
@@ -534,7 +534,7 @@ struct	in6_multistep {
 /*
  * Macros for looking up the in6_multi record for a given IP6 multicast
  * address on a given interface. If no matching record is found, "in6m"
- * returns NLL.
+ * returns NULL.
  */
 
 #define IN6_LOOKUP_MULTI(addr, ifp, in6m)			\
diff --git a/sys/netinet6/nd6.c b/sys/netinet6/nd6.c
index 4265b3152352..fbc53ccef5ab 100644
--- a/sys/netinet6/nd6.c
+++ b/sys/netinet6/nd6.c
@@ -1036,7 +1036,7 @@ nd6_free(rt)
 /*
  * Upper-layer reachability hint for Neighbor Unreachability Detection.
  *
- * XXX cost-effective metods?
+ * XXX cost-effective methods?
  */
 void
 nd6_nud_hint(rt, dst6, force)
@@ -1822,7 +1822,7 @@ nd6_output(ifp, origifp, m0, dst, rt0)
 		goto sendpkt;
 
 	/*
-	 * next hop determination.  This routine is derived from ether_outpout.
+	 * next hop determination.  This routine is derived from ether_output.
 	 */
 again:
 	if (rt) {
diff --git a/sys/netinet6/nd6_nbr.c b/sys/netinet6/nd6_nbr.c
index 4af0f1a8be5d..db6cde42dcaf 100644
--- a/sys/netinet6/nd6_nbr.c
+++ b/sys/netinet6/nd6_nbr.c
@@ -87,7 +87,7 @@ static int dad_maxtry = 15;	/* max # of *tries* to transmit DAD packet */
  * Input a Neighbor Solicitation Message.
  *
  * Based on RFC 2461
- * Based on RFC 2462 (duplicated address detection)
+ * Based on RFC 2462 (duplicate address detection)
  */
 void
 nd6_ns_input(m, off, icmp6len)
@@ -133,7 +133,7 @@ nd6_ns_input(m, off, icmp6len)
 	}
 
 	if (IN6_IS_ADDR_UNSPECIFIED(&saddr6)) {
-		/* dst has to be solicited node multicast address. */
+		/* dst has to be a solicited node multicast address. */
 		if (daddr6.s6_addr16[0] == IPV6_ADDR_INT16_MLL &&
 		    /* don't check ifindex portion */
 		    daddr6.s6_addr32[1] == 0 &&
@@ -280,7 +280,7 @@ nd6_ns_input(m, off, icmp6len)
 	if (tentative) {
 		/*
 		 * If source address is unspecified address, it is for
-		 * duplicated address detection.
+		 * duplicate address detection.
 		 *
 		 * If not, the packet is for addess resolution;
 		 * silently ignore it.
@@ -338,14 +338,14 @@ nd6_ns_input(m, off, icmp6len)
  *	- ND6 header source datalink address
  *
  * Based on RFC 2461
- * Based on RFC 2462 (duplicated address detection)
+ * Based on RFC 2462 (duplicate address detection)
  */
 void
 nd6_ns_output(ifp, daddr6, taddr6, ln, dad)
 	struct ifnet *ifp;
 	const struct in6_addr *daddr6, *taddr6;
 	struct llinfo_nd6 *ln;	/* for source address determination */
-	int dad;	/* duplicated address detection */
+	int dad;	/* duplicate address detection */
 {
 	struct mbuf *m;
 	struct ip6_hdr *ip6;
@@ -436,6 +436,10 @@ nd6_ns_output(ifp, daddr6, taddr6, ln, dad)
 		struct in6_addr *hsrc = NULL;
 
 		if (ln && ln->ln_hold) {
+			/*
+			 * assuming every packet in ln_hold has the same IP
+			 * header
+			 */
 			hip6 = mtod(ln->ln_hold, struct ip6_hdr *);
 			/* XXX pullup? */
 			if (sizeof(*hip6) < ln->ln_hold->m_len)
@@ -537,7 +541,7 @@ nd6_ns_output(ifp, daddr6, taddr6, ln, dad)
  * Neighbor advertisement input handling.
  *
  * Based on RFC 2461
- * Based on RFC 2462 (duplicated address detection)
+ * Based on RFC 2462 (duplicate address detection)
  *
  * the following items are not implemented yet:
  * - proxy advertisement delay rule (RFC2461 7.2.8, last paragraph, SHOULD)
@@ -1078,7 +1082,7 @@ nd6_dad_stoptimer(dp)
 }
 
 /*
- * Start Duplicated Address Detection (DAD) for specified interface address.
+ * Start Duplicate Address Detection (DAD) for specified interface address.
  */
 void
 nd6_dad_start(ifa, tick)
@@ -1265,33 +1269,8 @@ nd6_dad_timer(ifa)
 		}
 
 		if (dp->dad_ns_icount) {
-#if 0 /* heuristics */
-			/*
-			 * if
-			 * - we have sent many(?) DAD NS, and
-			 * - the number of NS we sent equals to the
-			 *   number of NS we've got, and
-			 * - we've got no NA
-			 * we may have a faulty network card/driver which
-			 * loops back multicasts to myself.
-			 */
-			if (3 < dp->dad_count
-			 && dp->dad_ns_icount == dp->dad_count
-			 && dp->dad_na_icount == 0) {
-				log(LOG_INFO, "DAD questionable for %s(%s): "
-				    "network card loops back multicast?\n",
-				    ip6_sprintf(&ia->ia_addr.sin6_addr),
-				    if_name(ifa->ifa_ifp));
-				/* XXX consider it a duplicate or not? */
-				/* duplicate++; */
-			} else {
-				/* We've seen NS, means DAD has failed. */
-				duplicate++;
-			}
-#else
 			/* We've seen NS, means DAD has failed. */
 			duplicate++;
-#endif
 		}
 
 		if (duplicate) {
@@ -1301,7 +1280,7 @@ nd6_dad_timer(ifa)
 		} else {
 			/*
 			 * We are done with DAD.  No NA came, no NS came.
-			 * duplicated address found.
+			 * No duplicate address found.
 			 */
 			ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
 
@@ -1342,7 +1321,7 @@ nd6_dad_duplicated(ifa)
 	ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
 	ia->ia6_flags |= IN6_IFF_DUPLICATED;
 
-	/* We are done with DAD, with duplicated address found. (failure) */
+	/* We are done with DAD, with duplicate address found. (failure) */
 	nd6_dad_stoptimer(dp);
 
 	log(LOG_ERR, "%s: DAD complete for %s - duplicate found\n",
diff --git a/sys/netinet6/nd6_rtr.c b/sys/netinet6/nd6_rtr.c
index 1b0792d7fc6c..3b53536dbeea 100644
--- a/sys/netinet6/nd6_rtr.c
+++ b/sys/netinet6/nd6_rtr.c
@@ -1600,10 +1600,6 @@ in6_ifadd(pr, ifid)
 	 * (4) it is easier to manage when an interface has addresses
 	 * with the same interface identifier, than to have multiple addresses
 	 * with different interface identifiers.
-	 *
-	 * Mobile IPv6 addition: allow for caller to specify a wished interface
-	 * ID. This is to not break connections when moving addresses between
-	 * interfaces.
 	 */
 	ifa = (struct ifaddr *)in6ifa_ifpforlinklocal(ifp, 0); /* 0 is OK? */
 	if (ifa)