diff --git a/ovn/northd/ovn-northd.8.xml b/ovn/northd/ovn-northd.8.xml
index 759d3dace..a33de3d95 100644
--- a/ovn/northd/ovn-northd.8.xml
+++ b/ovn/northd/ovn-northd.8.xml
@@ -1317,10 +1317,6 @@ nd_na {
         <p>
           These flows should not match IP fragments with nonzero offset.
         </p>
-
-        <p>
-          Details TBD.  Not yet implemented.
-        </p>
       </li>
 
       <li>
diff --git a/ovn/northd/ovn-northd.c b/ovn/northd/ovn-northd.c
index 74eefc6ca..0e137efde 100644
--- a/ovn/northd/ovn-northd.c
+++ b/ovn/northd/ovn-northd.c
@@ -5147,6 +5147,26 @@ build_lrouter_flows(struct hmap *datapaths, struct hmap *ports,
                           ds_cstr(&match), ds_cstr(&actions));
         }
 
+        /* UDP port unreachable */
+        for (int i = 0; i < op->lrp_networks.n_ipv4_addrs; i++) {
+            ds_clear(&match);
+            ds_clear(&actions);
+
+            ds_put_format(&match,
+                          "ip4 && ip4.dst == %s && !ip.later_frag && udp",
+                          op->lrp_networks.ipv4_addrs[i].addr_s);
+            ds_put_format(&actions,
+                          "icmp4 {"
+                          "eth.dst <-> eth.src; "
+                          "ip4.dst <-> ip4.src; "
+                          "ip.ttl = 255; "
+                          "icmp4.type = 3; "
+                          "icmp4.code = 3; "
+                          "next; };");
+            ovn_lflow_add(lflows, op->od, S_ROUTER_IN_IP_INPUT, 80,
+                          ds_cstr(&match), ds_cstr(&actions));
+        }
+
         ds_clear(&match);
         ds_put_cstr(&match, "ip4.dst == {");
         bool has_drop_ips = false;
diff --git a/tests/ovn.at b/tests/ovn.at
index b586afb4e..ee807f9c3 100644
--- a/tests/ovn.at
+++ b/tests/ovn.at
@@ -10344,3 +10344,79 @@ OVN_CHECK_PACKETS([hv1/vif1-tx.pcap], [vif1.expected])
 
 OVN_CLEANUP([hv1], [hv2])
 AT_CLEANUP
+
+AT_SETUP([ovn -- router port unreachable])
+AT_KEYWORDS([router-port-unreachable])
+AT_SKIP_IF([test $HAVE_PYTHON = no])
+ovn_start
+
+# test_ip_packet INPORT HV ETH_SRC ETH_DST IPV4_SRC IPV4_ROUTER L4_PROTCOL IP_CHKSUM EXP_IP_CHKSUM EXP_ICMP_CHKSUM EXP_ICMP_CODE
+#
+# Causes a packet to be received on INPORT of the hypervisor HV. The packet is an IPv4 packet with
+# ETH_SRC, ETH_DST, IPV4_SRC, IPV4_ROUTER, L4_PROTCOL, IP_CHKSUM as specified.
+# EXP_IP_CHKSUM and EXP_ICMP_CHKSUM are the ip and icmp checksums of the icmp frame generated by OVN logical router
+# EXP_ICMP_CODE are code and type of the icmp frame generated by OVN logical router
+#
+# INPORT is a lport number, e.g. 11 for vif11.
+# HV is a hypervisor number
+# ETH_SRC and ETH_DST are each 12 hex digits.
+# IPV4_SRC and IPV4_ROUTER are each 8 hex digits.
+# IP_CHKSUM, EXP_IP_CHSUM and EXP_ICMP_CHKSUM are each 4 hex digits
+test_ip_packet() {
+    local inport=$1 hv=$2 eth_src=$3 eth_dst=$4 ipv4_src=$5 ip_router=$6 l4_proto=$7 ip_chksum=$8
+    local exp_ip_chksum=$9 exp_icmp_chksum=${10} exp_icmp_code=${11}
+    shift 11
+
+    local ip_ttl=ff
+    local packet=${eth_dst}${eth_src}08004500001400004000${ip_ttl}${l4_proto}${ip_chksum}${ipv4_src}${ip_router}
+
+    local reply_icmp_ttl=fe
+    local icmp_data=00000000
+    local reply_icmp_payload=${exp_icmp_code}${exp_icmp_chksum}${icmp_data}
+    local reply=${eth_src}${eth_dst}08004500001c00004000${reply_icmp_ttl}01${exp_ip_chksum}${ip_router}${ipv4_src}${reply_icmp_payload}
+    echo $reply >> vif$inport.expected
+
+    as hv$hv ovs-appctl netdev-dummy/receive vif$inport $packet
+}
+
+ip_to_hex() {
+    printf "%02x%02x%02x%02x" "$@"
+}
+
+for i in 1 2; do
+    net_add n$i
+    ovn-nbctl ls-add sw$i
+
+    sim_add hv$i
+    as hv$i
+    ovs-vsctl add-br br-phys
+    ovn_attach n$i br-phys 192.168.$i.1
+
+    ovn-nbctl lsp-add sw$i sw$i-p${i}0 -- \
+        lsp-set-addresses sw$i-p${i}0 "00:00:00:00:00:0$i 192.168.$i.1"
+
+    ovs-vsctl -- add-port br-int vif$i -- \
+        set interface vif$i \
+        external-ids:iface-id=sw$i-p${i}0 \
+            options:tx_pcap=hv$i/vif$i-tx.pcap \
+            options:rxq_pcap=hv$i/vif$i-rx.pcap \
+            ofport-request=$i
+done
+
+ovn-nbctl lr-add lr0
+for i in 1 2; do
+    ovn-nbctl lrp-add lr0 lrp$i 00:00:00:00:ff:0$i 192.168.$i.254/24
+    ovn-nbctl -- lsp-add sw$i lrp$i-attachment \
+              -- set Logical_Switch_Port lrp$i-attachment type=router \
+                options:router-port=lrp$i addresses='"00:00:00:00:ff:'0$i'"'
+done
+
+OVN_POPULATE_ARP
+# allow some time for ovn-northd and ovn-controller to catch up.
+ovn-nbctl --wait=hv sync
+
+test_ip_packet 1 1 000000000001 00000000ff01 $(ip_to_hex 192 168 1 1) $(ip_to_hex 192 168 1 254) 11 0000 7dae fcfc 0303
+OVN_CHECK_PACKETS([hv1/vif1-tx.pcap], [vif1.expected])
+
+OVN_CLEANUP([hv1], [hv2])
+AT_CLEANUP
