diff --git a/lib/conntrack.c b/lib/conntrack.c
index 13c5ab628..33ea419a7 100644
--- a/lib/conntrack.c
+++ b/lib/conntrack.c
@@ -764,109 +764,59 @@ handle_alg_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx,
 }
 
 static void
-pat_packet(struct dp_packet *pkt, const struct conn *conn)
+pat_packet(struct dp_packet *pkt, const struct conn_key *key)
 {
-    if (conn->nat_action & NAT_ACTION_SRC) {
-        if (conn->key.nw_proto == IPPROTO_TCP) {
-            struct tcp_header *th = dp_packet_l4(pkt);
-            packet_set_tcp_port(pkt, conn->rev_key.dst.port, th->tcp_dst);
-        } else if (conn->key.nw_proto == IPPROTO_UDP) {
-            struct udp_header *uh = dp_packet_l4(pkt);
-            packet_set_udp_port(pkt, conn->rev_key.dst.port, uh->udp_dst);
-        }
-    } else if (conn->nat_action & NAT_ACTION_DST) {
-        if (conn->key.nw_proto == IPPROTO_TCP) {
-            packet_set_tcp_port(pkt, conn->rev_key.dst.port,
-                                conn->rev_key.src.port);
-        } else if (conn->key.nw_proto == IPPROTO_UDP) {
-            packet_set_udp_port(pkt, conn->rev_key.dst.port,
-                                conn->rev_key.src.port);
-        }
+    if (key->nw_proto == IPPROTO_TCP) {
+        packet_set_tcp_port(pkt, key->dst.port, key->src.port);
+    } else if (key->nw_proto == IPPROTO_UDP) {
+        packet_set_udp_port(pkt, key->dst.port, key->src.port);
     }
 }
 
-static void
-nat_packet(struct dp_packet *pkt, const struct conn *conn, bool related)
+static uint16_t
+nat_action_reverse(uint16_t nat_action)
 {
-    if (conn->nat_action & NAT_ACTION_SRC) {
-        pkt->md.ct_state |= CS_SRC_NAT;
-        if (conn->key.dl_type == htons(ETH_TYPE_IP)) {
-            struct ip_header *nh = dp_packet_l3(pkt);
-            packet_set_ipv4_addr(pkt, &nh->ip_src,
-                                 conn->rev_key.dst.addr.ipv4);
-        } else {
-            struct ovs_16aligned_ip6_hdr *nh6 = dp_packet_l3(pkt);
-            packet_set_ipv6_addr(pkt, conn->key.nw_proto,
-                                 nh6->ip6_src.be32,
-                                 &conn->rev_key.dst.addr.ipv6, true);
-        }
-        if (!related) {
-            pat_packet(pkt, conn);
-        }
-    } else if (conn->nat_action & NAT_ACTION_DST) {
-        pkt->md.ct_state |= CS_DST_NAT;
-        if (conn->key.dl_type == htons(ETH_TYPE_IP)) {
-            struct ip_header *nh = dp_packet_l3(pkt);
-            packet_set_ipv4_addr(pkt, &nh->ip_dst,
-                                 conn->rev_key.src.addr.ipv4);
-        } else {
-            struct ovs_16aligned_ip6_hdr *nh6 = dp_packet_l3(pkt);
-            packet_set_ipv6_addr(pkt, conn->key.nw_proto,
-                                 nh6->ip6_dst.be32,
-                                 &conn->rev_key.src.addr.ipv6, true);
-        }
-        if (!related) {
-            pat_packet(pkt, conn);
-        }
+    if (nat_action & NAT_ACTION_SRC) {
+        nat_action ^= NAT_ACTION_SRC;
+        nat_action |= NAT_ACTION_DST;
+    } else if (nat_action & NAT_ACTION_DST) {
+        nat_action ^= NAT_ACTION_DST;
+        nat_action |= NAT_ACTION_SRC;
     }
+    return nat_action;
 }
 
 static void
-un_pat_packet(struct dp_packet *pkt, const struct conn *conn)
+nat_packet_ipv4(struct dp_packet *pkt, const struct conn_key *key,
+                uint16_t nat_action)
 {
-    if (conn->nat_action & NAT_ACTION_SRC) {
-        if (conn->key.nw_proto == IPPROTO_TCP) {
-            struct tcp_header *th = dp_packet_l4(pkt);
-            packet_set_tcp_port(pkt, th->tcp_src, conn->key.src.port);
-        } else if (conn->key.nw_proto == IPPROTO_UDP) {
-            struct udp_header *uh = dp_packet_l4(pkt);
-            packet_set_udp_port(pkt, uh->udp_src, conn->key.src.port);
-        }
-    } else if (conn->nat_action & NAT_ACTION_DST) {
-        if (conn->key.nw_proto == IPPROTO_TCP) {
-            packet_set_tcp_port(pkt, conn->key.dst.port, conn->key.src.port);
-        } else if (conn->key.nw_proto == IPPROTO_UDP) {
-            packet_set_udp_port(pkt, conn->key.dst.port, conn->key.src.port);
-        }
+    struct ip_header *nh = dp_packet_l3(pkt);
+
+    if (nat_action & NAT_ACTION_SRC) {
+        packet_set_ipv4_addr(pkt, &nh->ip_src, key->dst.addr.ipv4);
+    } else if (nat_action & NAT_ACTION_DST) {
+        packet_set_ipv4_addr(pkt, &nh->ip_dst, key->src.addr.ipv4);
     }
 }
 
 static void
-reverse_pat_packet(struct dp_packet *pkt, const struct conn *conn)
+nat_packet_ipv6(struct dp_packet *pkt, const struct conn_key *key,
+                uint16_t nat_action)
 {
-    if (conn->nat_action & NAT_ACTION_SRC) {
-        if (conn->key.nw_proto == IPPROTO_TCP) {
-            struct tcp_header *th_in = dp_packet_l4(pkt);
-            packet_set_tcp_port(pkt, conn->key.src.port,
-                                th_in->tcp_dst);
-        } else if (conn->key.nw_proto == IPPROTO_UDP) {
-            struct udp_header *uh_in = dp_packet_l4(pkt);
-            packet_set_udp_port(pkt, conn->key.src.port,
-                                uh_in->udp_dst);
-        }
-    } else if (conn->nat_action & NAT_ACTION_DST) {
-        if (conn->key.nw_proto == IPPROTO_TCP) {
-            packet_set_tcp_port(pkt, conn->key.src.port,
-                                conn->key.dst.port);
-        } else if (conn->key.nw_proto == IPPROTO_UDP) {
-            packet_set_udp_port(pkt, conn->key.src.port,
-                                conn->key.dst.port);
-        }
+    struct ovs_16aligned_ip6_hdr *nh6 = dp_packet_l3(pkt);
+
+    if (nat_action & NAT_ACTION_SRC) {
+        packet_set_ipv6_addr(pkt, key->nw_proto, nh6->ip6_src.be32,
+                             &key->dst.addr.ipv6, true);
+    } else if (nat_action & NAT_ACTION_DST) {
+        packet_set_ipv6_addr(pkt, key->nw_proto, nh6->ip6_dst.be32,
+                             &key->src.addr.ipv6, true);
     }
 }
 
 static void
-reverse_nat_packet(struct dp_packet *pkt, const struct conn *conn)
+nat_inner_packet(struct dp_packet *pkt, struct conn_key *key,
+                 uint16_t nat_action)
 {
     char *tail = dp_packet_tail(pkt);
     uint16_t pad = dp_packet_l2_pad_size(pkt);
@@ -875,98 +825,77 @@ reverse_nat_packet(struct dp_packet *pkt, const struct conn *conn)
     uint16_t orig_l3_ofs = pkt->l3_ofs;
     uint16_t orig_l4_ofs = pkt->l4_ofs;
 
-    if (conn->key.dl_type == htons(ETH_TYPE_IP)) {
-        struct ip_header *nh = dp_packet_l3(pkt);
-        struct icmp_header *icmp = dp_packet_l4(pkt);
-        struct ip_header *inner_l3 = (struct ip_header *) (icmp + 1);
-        /* This call is already verified to succeed during the code path from
-         * 'conn_key_extract()' which calls 'extract_l4_icmp()'. */
-        extract_l3_ipv4(&inner_key, inner_l3, tail - ((char *)inner_l3) - pad,
+    void *l3 = dp_packet_l3(pkt);
+    void *l4 = dp_packet_l4(pkt);
+    void *inner_l3;
+    /* These calls are already verified to succeed during the code path from
+     * 'conn_key_extract()' which calls
+     * 'extract_l4_icmp()'/'extract_l4_icmp6()'. */
+    if (key->dl_type == htons(ETH_TYPE_IP)) {
+        inner_l3 = (char *) l4 + sizeof(struct icmp_header);
+        extract_l3_ipv4(&inner_key, inner_l3, tail - ((char *) inner_l3) - pad,
                         &inner_l4, false);
-        pkt->l3_ofs += (char *) inner_l3 - (char *) nh;
-        pkt->l4_ofs += inner_l4 - (char *) icmp;
+    } else {
+        inner_l3 = (char *) l4 + sizeof(struct icmp6_data_header);
+        extract_l3_ipv6(&inner_key, inner_l3, tail - ((char *) inner_l3) - pad,
+                        &inner_l4);
+    }
+    pkt->l3_ofs += (char *) inner_l3 - (char *) l3;
+    pkt->l4_ofs += inner_l4 - (char *) l4;
 
-        if (conn->nat_action & NAT_ACTION_SRC) {
-            packet_set_ipv4_addr(pkt, &inner_l3->ip_src,
-                                 conn->key.src.addr.ipv4);
-        } else if (conn->nat_action & NAT_ACTION_DST) {
-            packet_set_ipv4_addr(pkt, &inner_l3->ip_dst,
-                                 conn->key.dst.addr.ipv4);
-        }
+    /* Reverse the key for inner packet. */
+    struct conn_key rev_key = *key;
+    conn_key_reverse(&rev_key);
+
+    pat_packet(pkt, &rev_key);
+
+    if (key->dl_type == htons(ETH_TYPE_IP)) {
+        nat_packet_ipv4(pkt, &rev_key, nat_action);
 
-        reverse_pat_packet(pkt, conn);
+        struct icmp_header *icmp = (struct icmp_header *) l4;
         icmp->icmp_csum = 0;
         icmp->icmp_csum = csum(icmp, tail - (char *) icmp - pad);
     } else {
-        struct ovs_16aligned_ip6_hdr *nh6 = dp_packet_l3(pkt);
-        struct icmp6_data_header *icmp6 = dp_packet_l4(pkt);
-        struct ovs_16aligned_ip6_hdr *inner_l3_6 =
-            (struct ovs_16aligned_ip6_hdr *) (icmp6 + 1);
-        /* This call is already verified to succeed during the code path from
-         * 'conn_key_extract()' which calls 'extract_l4_icmp6()'. */
-        extract_l3_ipv6(&inner_key, inner_l3_6,
-                        tail - ((char *)inner_l3_6) - pad,
-                        &inner_l4);
-        pkt->l3_ofs += (char *) inner_l3_6 - (char *) nh6;
-        pkt->l4_ofs += inner_l4 - (char *) icmp6;
-
-        if (conn->nat_action & NAT_ACTION_SRC) {
-            packet_set_ipv6_addr(pkt, conn->key.nw_proto,
-                                 inner_l3_6->ip6_src.be32,
-                                 &conn->key.src.addr.ipv6, true);
-        } else if (conn->nat_action & NAT_ACTION_DST) {
-            packet_set_ipv6_addr(pkt, conn->key.nw_proto,
-                                 inner_l3_6->ip6_dst.be32,
-                                 &conn->key.dst.addr.ipv6, true);
-        }
-        reverse_pat_packet(pkt, conn);
+        nat_packet_ipv6(pkt, &rev_key, nat_action);
+
+        struct icmp6_data_header *icmp6 = (struct icmp6_data_header *) l4;
         icmp6->icmp6_base.icmp6_cksum = 0;
-        icmp6->icmp6_base.icmp6_cksum = packet_csum_upperlayer6(nh6, icmp6,
-            IPPROTO_ICMPV6, tail - (char *) icmp6 - pad);
+        icmp6->icmp6_base.icmp6_cksum =
+            packet_csum_upperlayer6(l3, icmp6, IPPROTO_ICMPV6,
+                                    tail - (char *) icmp6 - pad);
     }
+
     pkt->l3_ofs = orig_l3_ofs;
     pkt->l4_ofs = orig_l4_ofs;
 }
 
 static void
-un_nat_packet(struct dp_packet *pkt, const struct conn *conn,
-              bool related)
+nat_packet(struct dp_packet *pkt, struct conn *conn, bool reply, bool related)
 {
-    if (conn->nat_action & NAT_ACTION_SRC) {
-        pkt->md.ct_state |= CS_DST_NAT;
-        if (conn->key.dl_type == htons(ETH_TYPE_IP)) {
-            struct ip_header *nh = dp_packet_l3(pkt);
-            packet_set_ipv4_addr(pkt, &nh->ip_dst,
-                                 conn->key.src.addr.ipv4);
-        } else {
-            struct ovs_16aligned_ip6_hdr *nh6 = dp_packet_l3(pkt);
-            packet_set_ipv6_addr(pkt, conn->key.nw_proto,
-                                 nh6->ip6_dst.be32,
-                                 &conn->key.src.addr.ipv6, true);
-        }
+    struct conn_key *key = reply ? &conn->key : &conn->rev_key;
+    uint16_t nat_action = reply ? nat_action_reverse(conn->nat_action)
+                                : conn->nat_action;
 
-        if (OVS_UNLIKELY(related)) {
-            reverse_nat_packet(pkt, conn);
-        } else {
-            un_pat_packet(pkt, conn);
-        }
-    } else if (conn->nat_action & NAT_ACTION_DST) {
+    /* Update ct_state. */
+    if (nat_action & NAT_ACTION_SRC) {
         pkt->md.ct_state |= CS_SRC_NAT;
-        if (conn->key.dl_type == htons(ETH_TYPE_IP)) {
-            struct ip_header *nh = dp_packet_l3(pkt);
-            packet_set_ipv4_addr(pkt, &nh->ip_src,
-                                 conn->key.dst.addr.ipv4);
-        } else {
-            struct ovs_16aligned_ip6_hdr *nh6 = dp_packet_l3(pkt);
-            packet_set_ipv6_addr(pkt, conn->key.nw_proto,
-                                 nh6->ip6_src.be32,
-                                 &conn->key.dst.addr.ipv6, true);
-        }
+    } else if (nat_action & NAT_ACTION_DST) {
+        pkt->md.ct_state |= CS_DST_NAT;
+    }
+
+    /* Reverse the key for outer header. */
+    if (key->dl_type == htons(ETH_TYPE_IP)) {
+        nat_packet_ipv4(pkt, key, nat_action);
+    } else {
+        nat_packet_ipv6(pkt, key, nat_action);
+    }
 
+    if (nat_action & NAT_ACTION_SRC || nat_action & NAT_ACTION_DST) {
         if (OVS_UNLIKELY(related)) {
-            reverse_nat_packet(pkt, conn);
+            nat_action = nat_action_reverse(nat_action);
+            nat_inner_packet(pkt, key, nat_action);
         } else {
-            un_pat_packet(pkt, conn);
+            pat_packet(pkt, key);
         }
     }
 }
@@ -1082,7 +1011,7 @@ conn_not_found(struct conntrack *ct, struct dp_packet *pkt,
                 memcpy(nc, nat_conn, sizeof *nc);
             }
 
-            nat_packet(pkt, nc, ctx->icmp_related);
+            nat_packet(pkt, nc, false, ctx->icmp_related);
             memcpy(&nat_conn->key, &nc->rev_key, sizeof nat_conn->key);
             memcpy(&nat_conn->rev_key, &nc->key, sizeof nat_conn->rev_key);
             nat_conn->conn_type = CT_CONN_TYPE_UN_NAT;
@@ -1185,11 +1114,8 @@ handle_nat(struct dp_packet *pkt, struct conn *conn,
         if (pkt->md.ct_state & (CS_SRC_NAT | CS_DST_NAT)) {
             pkt->md.ct_state &= ~(CS_SRC_NAT | CS_DST_NAT);
         }
-        if (reply) {
-            un_nat_packet(pkt, conn, related);
-        } else {
-            nat_packet(pkt, conn, related);
-        }
+
+        nat_packet(pkt, conn, reply, related);
     }
 }
 
diff --git a/tests/system-traffic.at b/tests/system-traffic.at
index bad875b08..c4e9849b7 100644
--- a/tests/system-traffic.at
+++ b/tests/system-traffic.at
@@ -7089,6 +7089,113 @@ recirc_id(0),in_port(br-underlay),ct_state(+trk),eth(src=f0:00:00:01:01:02,dst=f
 OVS_TRAFFIC_VSWITCHD_STOP
 AT_CLEANUP
 
+AT_SETUP([conntrack - ICMP from different source related with NAT])
+AT_SKIP_IF([test $HAVE_NC = no])
+AT_SKIP_IF([test $HAVE_TCPDUMP = no])
+CHECK_CONNTRACK()
+CHECK_CONNTRACK_NAT()
+OVS_TRAFFIC_VSWITCHD_START()
+
+ADD_NAMESPACES(client, server)
+
+ADD_VETH(client, client, br0, "192.168.20.10/24", "00:00:00:00:20:10")
+ADD_VETH(server, server, br0, "192.168.10.20/24", "00:00:00:00:10:20")
+
+dnl Send traffic from client to CT, do DNAT if the traffic is new otherwise send it to server
+AT_DATA([flows.txt], [dnl
+table=0,ip,actions=ct(table=1,zone=42,nat)
+table=1,in_port=ovs-client,ip,ct_state=+trk+new,actions=ct(commit,table=2,zone=42,nat(dst=192.168.10.20)
+table=1,icmp,ct_state=+trk+rel-rpl,actions=ct(commit,table=2,zone=42,nat)
+table=1,ip,actions=resubmit(,2)
+table=2,in_port=ovs-client,ip,ct_state=+trk+new,actions=output:ovs-server
+table=2,in_port=ovs-client,icmp,ct_state=+trk+rel,actions=output:ovs-server
+table=2,in_port=ovs-server,icmp,ct_state=+trk+rel,actions=output:ovs-client
+table=2,in_port=ovs-server,ip,ct_state=+trk+rpl,actions=output:ovs-client
+])
+
+AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
+
+rm server.pcap
+OVS_DAEMONIZE([tcpdump -l -U -i ovs-server -w server.pcap 2>tcpdump0_err], [tcpdump0.pid])
+OVS_WAIT_UNTIL([grep "listening" tcpdump0_err])
+
+dnl Send UDP client->server
+AT_CHECK([ovs-ofctl packet-out br0 "in_port=ovs-client,\
+packet=00000000102000000000201008004500001C000040000A11C762C0A8140AC0A814140001000200080000,actions=resubmit(,0)"])
+dnl Send UDP response server->client
+AT_CHECK([ovs-ofctl packet-out br0 "in_port=ovs-server,\
+packet=00000000201000000000102008004500001C000040000A11D162C0A80A14C0A8140A0002000100080000,actions=resubmit(,0)"])
+dnl Fake router sending ICMP need frag router->server
+AT_CHECK([ovs-ofctl packet-out br0 "in_port=ovs-client,\
+packet=000000001020000000002000080045000038011F0000FF011140C0A81401C0A814140304F778000005784500001C000040000A11C762C0A81414C0A8140A0002000100080000,\
+actions=resubmit(,0)"
+])
+
+AT_CHECK([ovs-appctl revalidator/purge], [0])
+AT_CHECK([ovs-ofctl -O OpenFlow15 dump-flows br0 | ofctl_strip | sort ], [0], [dnl
+ n_packets=3, n_bytes=154, reset_counts ip actions=ct(table=1,zone=42,nat)
+ table=1, n_packets=1, n_bytes=42, reset_counts ct_state=+new+trk,ip,in_port=1 actions=ct(commit,table=2,zone=42,nat(dst=192.168.10.20))
+ table=1, n_packets=1, n_bytes=42, reset_counts ip actions=resubmit(,2)
+ table=1, n_packets=1, n_bytes=70, reset_counts ct_state=+rel-rpl+trk,icmp actions=ct(commit,table=2,zone=42,nat)
+ table=2, n_packets=1, n_bytes=42, reset_counts ct_state=+new+trk,ip,in_port=1 actions=output:2
+ table=2, n_packets=1, n_bytes=42, reset_counts ct_state=+rpl+trk,ip,in_port=2 actions=output:1
+ table=2, n_packets=1, n_bytes=70, reset_counts ct_state=+rel+trk,icmp,in_port=1 actions=output:2
+ table=2, reset_counts ct_state=+rel+trk,icmp,in_port=2 actions=output:1
+OFPST_FLOW reply (OF1.5):
+])
+
+AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "192.168.20.10"], [0], [dnl
+udp,orig=(src=192.168.20.10,dst=192.168.20.20,sport=1,dport=2),reply=(src=192.168.10.20,dst=192.168.20.10,sport=2,dport=1),zone=42
+])
+
+OVS_WAIT_UNTIL([ovs-pcap server.pcap | grep 000000001020000000002000])
+
+AT_CHECK([ovs-pcap server.pcap | grep 000000001020000000002000], [0], [dnl
+000000001020000000002000080045000038011f0000ff011b40c0a81401c0a80a140304f778000005784500001c000040000a11d162c0a80a14c0a8140a0002000100080000
+])
+
+dnl Check the ICMP error in reply direction
+AT_CHECK([ovs-appctl dpctl/flush-conntrack zone=42])
+
+rm client.pcap
+OVS_DAEMONIZE([tcpdump -l -U -i ovs-client -w client.pcap 2>tcpdump1_err], [tcpdump1.pid])
+OVS_WAIT_UNTIL([grep "listening" tcpdump1_err])
+
+dnl Send UDP client->server
+AT_CHECK([ovs-ofctl packet-out br0 "in_port=ovs-client,\
+packet=00000000102000000000201008004500001C000040000A11C762C0A8140AC0A814140001000200080000,actions=resubmit(,0)"])
+dnl Fake router sending ICMP need frag router->client
+AT_CHECK([ovs-ofctl packet-out br0 "in_port=ovs-server,\
+packet=000000002010000000002000080045000038011F0000FF01114AC0A81401C0A8140A0304F778000005784500001C000040000A11D162C0A8140AC0A80A140001000200080000,\
+actions=resubmit(,0)"
+])
+
+AT_CHECK([ovs-appctl revalidator/purge], [0])
+AT_CHECK([ovs-ofctl -O OpenFlow15 dump-flows br0 | ofctl_strip | sort ], [0], [dnl
+ n_packets=5, n_bytes=266, reset_counts ip actions=ct(table=1,zone=42,nat)
+ table=1, n_packets=1, n_bytes=70, reset_counts ct_state=+rel-rpl+trk,icmp actions=ct(commit,table=2,zone=42,nat)
+ table=1, n_packets=2, n_bytes=112, reset_counts ip actions=resubmit(,2)
+ table=1, n_packets=2, n_bytes=84, reset_counts ct_state=+new+trk,ip,in_port=1 actions=ct(commit,table=2,zone=42,nat(dst=192.168.10.20))
+ table=2, n_packets=1, n_bytes=42, reset_counts ct_state=+rpl+trk,ip,in_port=2 actions=output:1
+ table=2, n_packets=1, n_bytes=70, reset_counts ct_state=+rel+trk,icmp,in_port=1 actions=output:2
+ table=2, n_packets=1, n_bytes=70, reset_counts ct_state=+rel+trk,icmp,in_port=2 actions=output:1
+ table=2, n_packets=2, n_bytes=84, reset_counts ct_state=+new+trk,ip,in_port=1 actions=output:2
+OFPST_FLOW reply (OF1.5):
+])
+
+AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "192.168.20.10"], [0], [dnl
+udp,orig=(src=192.168.20.10,dst=192.168.20.20,sport=1,dport=2),reply=(src=192.168.10.20,dst=192.168.20.10,sport=2,dport=1),zone=42
+])
+
+OVS_WAIT_UNTIL([ovs-pcap client.pcap | grep 000000002010000000002000])
+
+AT_CHECK([ovs-pcap client.pcap | grep 000000002010000000002000], [0], [dnl
+000000002010000000002000080045000038011f0000ff011137c0a81414c0a8140a0304f778000005784500001c000040000a11c762c0a8140ac0a814140001000200080000
+])
+
+OVS_TRAFFIC_VSWITCHD_STOP
+AT_CLEANUP
+
 AT_BANNER([IGMP])
 
 AT_SETUP([IGMP - flood under normal action])
