diff --git a/doc/plan.org b/doc/plan.org
index 87a1fb1..46c2b45 100644
--- a/doc/plan.org
+++ b/doc/plan.org
@@ -4986,6 +4986,8 @@ Using
 
 #+END_CENTER
 
+--> gateway not reachable! -> need to verify neighbor discovery
+
 ** References / Follow up
 *** RFC 791 IPv4 https://tools.ietf.org/html/rfc791
 *** RFC 792 ICMP https://tools.ietf.org/html/rfc792
diff --git a/p4src/actions_delta_checksum.p4 b/p4src/actions_delta_checksum.p4
index 9192f13..5fc1c60 100644
--- a/p4src/actions_delta_checksum.p4
+++ b/p4src/actions_delta_checksum.p4
@@ -37,4 +37,29 @@ action v6sum() {
     meta.v6sum = meta.v6sum + (bit<16>) hdr.ipv6.next_header;  // 8 bit
 }
 
+action delta_udp_from_v4_to_v6()
+{
+    v4sum();
+    v6sum();
+    bit<16> diff = meta.v6sum - meta.v4sum;
+    hdr.udp.checksum = hdr.udp.checksum + ~diff +1;
+}
+
+action delta_tcp_from_v4_to_v6()
+{
+    v4sum();
+    v6sum();
+    bit<16> diff = meta.v6sum - meta.v4sum;
+    hdr.tcp.checksum = hdr.tcp.checksum + ~diff +1;
+}
+
+action delta_ipv4_from_v6_to_v4()
+{
+    v4sum();
+    v6sum();
+    bit<16> diff = meta.v6sum - meta.v4sum;
+    hdr.tcp.checksum = hdr.tcp.checksum + ~diff +1;
+}
+
+
 #endif
\ No newline at end of file
diff --git a/p4src/checksum_diff.p4 b/p4src/checksum_diff.p4
index 6d48f42..12e925a 100644
--- a/p4src/checksum_diff.p4
+++ b/p4src/checksum_diff.p4
@@ -85,23 +85,14 @@ control MyIngress(inout headers hdr,
                 }
                 if(hdr.udp.isValid()) {
                     #ifdef USE_NICO_DELTA_CHECKSUM
-                    v4sum();
-                    v6sum();
-                    bit<16> diff = meta.v6sum - meta.v4sum;
-                    hdr.udp.checksum = hdr.udp.checksum + ~diff +1;
-//                    hdr.udp.checksum = ~diff;
-
+                    delta_udp_from_v4_to_v6();
                     #else
                     meta.chk_udp_v6 = 1;
                     #endif
                 }
                 if(hdr.tcp.isValid()) {
                     #ifdef USE_NICO_DELTA_CHECKSUM
-                    v4sum();
-                    v6sum();
-                    bit<16> diff = meta.v6sum - meta.v4sum;
-                    hdr.tcp.checksum = hdr.tcp.checksum + ~diff +1;
-
+                    delta_tcp_from_v4_to_v6();
                     #else
 
                     meta.chk_tcp_v6 = 1;