diff --git a/sys/dev/virtio/network/if_vtnet.c b/sys/dev/virtio/network/if_vtnet.c
--- a/sys/dev/virtio/network/if_vtnet.c
+++ b/sys/dev/virtio/network/if_vtnet.c
@@ -1542,6 +1542,16 @@
 		}
 
 		m->m_len = size;
+#ifndef __NO_STRICT_ALIGNMENT
+		/*
+		 * Ensure that headers following the Ethernet header are
+		 * aligned.  Our IP/TCP/UDP implementations assume this.
+		 */
+		if (((uintptr_t)m->m_data & 0x3) == 0) {
+			m->m_len -= 2;
+			m->m_data += 2;
+		}
+#endif
 		if (m_head != NULL) {
 			m_tail->m_next = m;
 			m_tail = m;
@@ -3266,12 +3276,16 @@
 	device_t dev;
 	if_t ifp;
 	struct vtnet_rxq *rxq;
-	int i, clustersz, error;
+	int i, clustersz, error, mtu;
 
 	dev = sc->vtnet_dev;
 	ifp = sc->vtnet_ifp;
 
-	clustersz = vtnet_rx_cluster_size(sc, if_getmtu(ifp));
+	mtu = if_getmtu(ifp);
+#ifndef __NO_STRICT_ALIGNMENT
+	mtu += 2;
+#endif
+	clustersz = vtnet_rx_cluster_size(sc, mtu);
 	sc->vtnet_rx_clustersz = clustersz;
 
 	if (sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG) {