diff --git a/src/yggdrasil/icmpv6.go b/src/yggdrasil/icmpv6.go
index f96a9c9a..85a6bbb7 100644
--- a/src/yggdrasil/icmpv6.go
+++ b/src/yggdrasil/icmpv6.go
@@ -129,7 +129,8 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 			response, err := i.handle_ndp(datain[ipv6.HeaderLen:])
 			if err == nil {
 				// Create our ICMPv6 response
-				responsePacket, err := i.create_icmpv6_tun(ipv6Header.Src, ipv6.ICMPTypeNeighborAdvertisement, 0, response)
+				responsePacket, err := i.create_icmpv6_tun(ipv6Header.Src, ipv6.ICMPTypeNeighborAdvertisement, 0,
+					&icmp.DefaultMessageBody{ Data: response })
 				if err != nil {
 					return nil, err
 				}
@@ -148,7 +149,7 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 	return nil, nil
 }
 
-func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICMPType, mcode int, mbody []byte) ([]byte, error) {
+func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
 	// Pass through to create_icmpv6_tun
 	ipv6packet, err := i.create_icmpv6_tun(dst, mtype, mcode, mbody)
 	if err != nil {
@@ -156,7 +157,7 @@ func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICM
 	}
 
 	// Create the response buffer
-	dataout := make([]byte, ETHER+ipv6.HeaderLen+len(mbody))
+	dataout := make([]byte, ETHER+ipv6.HeaderLen+mbody.Len(0))
 
 	// Populate the response ethernet headers
 	copy(dataout[:6], dstmac[:6])
@@ -168,12 +169,12 @@ func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICM
 	return dataout, nil
 }
 
-func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, mbody []byte) ([]byte, error) {
+func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
 	// Create the IPv6 header
 	ipv6Header := ipv6.Header{
 		Version:    ipv6.Version,
 		NextHeader: 58,
-		PayloadLen: len(mbody),
+		PayloadLen: mbody.Len(0),
 		HopLimit:   255,
 		Src:        i.mylladdr,
 		Dst:        dst,
@@ -183,7 +184,7 @@ func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, m
 	icmpMessage := icmp.Message{
 		Type: mtype,
 		Code: mcode,
-		Body: &icmp.DefaultMessageBody{Data: mbody},
+		Body: mbody,
 	}
 
 	// Convert the IPv6 header into []byte
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index e0884ef4..abd51c41 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -23,6 +23,8 @@ package yggdrasil
 //  The router then runs some sanity checks before passing it to the tun
 
 import "time"
+import "golang.org/x/net/icmp"
+import "golang.org/x/net/ipv6"
 
 //import "fmt"
 //import "net"
@@ -145,9 +147,31 @@ func (r *router) sendPacket(bs []byte) {
 		fallthrough
 	//default: go func() { sinfo.send<-bs }()
 	default:
+		// Generate an ICMPv6 Packet Too Big for packets larger than session MTU
 		if len(bs) > int(sinfo.getMTU()) {
-			// TODO: Send ICMPv6 Packet Too Big back to the TUN/TAP adapter
 			sinfo.core.log.Printf("Packet length %d exceeds session MTU %d", len(bs), sinfo.getMTU())
+
+			// Get the size of the oversized payload, up to a max of 900 bytes
+			window := 900
+			if int(sinfo.getMTU()) < window {
+				window = int(sinfo.getMTU())
+			}
+
+			// Create the Packet Too Big response
+			ptb := &icmp.PacketTooBig{
+				MTU: int(sinfo.getMTU()),
+				Data: bs[:window],
+			}
+
+			// Create the ICMPv6 response from it
+			icmpv6Buf, err := r.core.tun.icmpv6.create_icmpv6_tun(bs[8:24], ipv6.ICMPTypePacketTooBig, 0, ptb)
+			if err == nil {
+				sinfo.core.log.Printf("Sending ICMPv6 Message Too Big")
+				r.recv <- icmpv6Buf
+			}
+
+			// Don't continue - drop the packet
+			return
 		}
 		select {
 		case sinfo.send <- bs: