--- sys/netinet/myloop_masklen.h
+++ sys/netinet/myloop_masklen.h
@@ -0,0 +1,7 @@
+#include "opt_myloop_masklen.h"
+
+#ifndef MYLOOP_MASKLEN
+#define	IN_MY_LOOP(i)		(((u_int32_t)(i) & IN_CLASSA_NET) == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
+#else
+#define	IN_MY_LOOP(i)		(((u_int32_t)(i) & (INADDR_BROADCAST << (32 - MYLOOP_MASKLEN))) == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
+#endif
--- sys/netinet/in.c
+++ sys/netinet/in.c
@@ -48,6 +48,7 @@
 #include <net/route.h>
 
 #include <netinet/in.h>
+#include <netinet/myloop_masklen.h>
 #include <netinet/in_var.h>
 #include <netinet/in_pcb.h>
 
@@ -112,11 +113,11 @@
 	register u_long i = ntohl(in.s_addr);
 	register u_long net;
 
-	if (IN_EXPERIMENTAL(i) || IN_MULTICAST(i))
+	if (IN_EXPERIMENTAL(i) || IN_MULTICAST(i) || IN_MY_LOOP(i))
 		return (0);
 	if (IN_CLASSA(i)) {
 		net = i & IN_CLASSA_NET;
-		if (net == 0 || net == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
+		if (net == 0)
 			return (0);
 	}
 	return (1);
--- sys/netinet/ip_icmp.c
+++ sys/netinet/ip_icmp.c
@@ -50,6 +50,7 @@
 
 #define _IP_VHL
 #include <netinet/in.h>
+#include <netinet/myloop_masklen.h>
 #include <netinet/in_systm.h>
 #include <netinet/in_var.h>
 #include <netinet/ip.h>
@@ -612,8 +613,7 @@
 	int optlen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof(struct ip);
 
 	if (!in_canforward(ip->ip_src) &&
-	    ((ntohl(ip->ip_src.s_addr) & IN_CLASSA_NET) !=
-	     (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))) {
+            !IN_MY_LOOP(ntohl(ip->ip_src.s_addr))) {
 		m_freem(m);	/* Bad return address */
 		goto done;	/* Ip_output() will check for broadcast */
 	}
--- sys/netinet/ip_input.c
+++ sys/netinet/ip_input.c
@@ -65,6 +65,7 @@
 #include <net/intrq.h>
 
 #include <netinet/in.h>
+#include <netinet/myloop_masklen.h>
 #include <netinet/in_systm.h>
 #include <netinet/in_var.h>
 #include <netinet/ip.h>
@@ -347,8 +348,9 @@
 	}
 
 	/* 127/8 must not appear on wire - RFC1122 */
-	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
+	/* Local change: 127/MYLOOP_MASKLEN */
+	if (IN_MY_LOOP(ntohl(ip->ip_dst.s_addr)) ||
+	    IN_MY_LOOP(ntohl(ip->ip_src.s_addr))) {
 		if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) == 0) {
 			ipstat.ips_badaddr++;
 			goto bad;
--- sys/i386/conf/LINT
+++ sys/i386/conf/LINT
@@ -425,6 +425,11 @@
 # mchain library. It can be either loaded as KLD or compiled into kernel
 options 	LIBMCHAIN		#mbuf management library
 
+# Usually kernel must to drop any external packet with src in 127/8
+# But it is useful in clusters narrow this mask in kernel to use
+# some nets in 127/8 for kernels interoperate in cluster.
+options 	MYLOOP_MASKLEN=8
+
 # netgraph(4). Enable the base netgraph code with the NETGRAPH option.
 # Individual node types can be enabled with the corresponding option
 # listed below; however, this is not strictly necessary as netgraph
--- sys/netinet/ip_output.c
+++ sys/netinet/ip_output.c
@@ -57,6 +57,7 @@
 #include <net/route.h>
 
 #include <netinet/in.h>
+#include <netinet/myloop_masklen.h>
 #include <netinet/in_systm.h>
 #include <netinet/ip.h>
 #include <netinet/in_pcb.h>
@@ -772,8 +773,9 @@
 	ip_fw_fwd_addr = NULL;
 pass:
 	/* 127/8 must not appear on wire - RFC1122. */
-	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
+	/* Local change: 127/MYLOOP_MASKLEN */
+	if (IN_MY_LOOP(ntohl(ip->ip_dst.s_addr)) ||
+	    IN_MY_LOOP(ntohl(ip->ip_src.s_addr))) {
 		if ((ifp->if_flags & IFF_LOOPBACK) == 0) {
 			ipstat.ips_badaddr++;
 			error = EADDRNOTAVAIL;
--- sys/conf/options
+++ sys/conf/options
@@ -297,6 +297,8 @@
 TCPDEBUG
 TCP_DROP_SYNFIN		opt_tcp_input.h
 XBONEHACK
+# For interconnect beetween kernels in claster
+MYLOOP_MASKLEN
 MBUF_STRESS_TEST	opt_mbuf_stress_test.h
 
 # Netgraph(4). Use option NETGRAPH to enable the base netgraph code.