Index: if_trunk.c
===================================================================
RCS file: /cvs/src/sys/net/if_trunk.c,v
retrieving revision 1.99
diff -u -p -r1.99 if_trunk.c
--- if_trunk.c	15 May 2015 10:15:13 -0000	1.99
+++ if_trunk.c	26 May 2015 03:02:09 -0000
@@ -315,11 +315,18 @@ trunk_port_create(struct trunk_softc *tr
 			printf("%s: first port, setting trunk mtu %u\n",
 			    tr->tr_ifname, ifp->if_mtu);
 		tr->tr_ac.ac_if.if_mtu = ifp->if_mtu;
-		tr->tr_ac.ac_if.if_hardmtu = ifp->if_mtu;
-	} else if (tr->tr_ac.ac_if.if_mtu != ifp->if_mtu) {
-		printf("%s: adding %s failed, MTU %u != %u\n", tr->tr_ifname,
-		    ifp->if_xname, ifp->if_mtu, tr->tr_ac.ac_if.if_mtu);
-		return (EINVAL);
+		tr->tr_ac.ac_if.if_hardmtu = ifp->if_hardmtu;
+	} else {
+		u_int hardmtu = MIN(ifp->if_hardmtu,
+		    tr->tr_ac.ac_if.if_hardmtu);
+
+		if (tr->tr_ac.ac_if.if_mtu > hardmtu) {
+			printf("%s: adding %s failed, MTU %u > hard MTU%u\n",
+			    tr->tr_ifname, ifp->if_xname,
+			    tr->tr_ac.ac_if.if_mtu, ifp->if_hardmtu);
+			return (EINVAL);
+		}
+		tr->tr_ac.ac_if.if_hardmtu = hardmtu;
 	}
 
 	if ((error = ifpromisc(ifp, 1)) != 0)