diff --git a/src/configInterface.cpp b/src/configInterface.cpp
index ca78d80..5f20741 100644
--- a/src/configInterface.cpp
+++ b/src/configInterface.cpp
@@ -118,6 +118,7 @@ void processRelayNotification(std::deque<swss::KeyOpFieldsValuesTuple> &entries,
 
         relay_config intf;
         intf.is_option_79 = true;
+        intf.is_interface_id = false;
         intf.interface = vlan;
         intf.db = nullptr;
         for (auto &fieldValue: fieldValues) {
@@ -135,6 +136,9 @@ void processRelayNotification(std::deque<swss::KeyOpFieldsValuesTuple> &entries,
             if(f == "dhcpv6_option|rfc6939_support" && v == "false") {
                 intf.is_option_79 = false;
             }
+            if(f == "dhcpv6_option|interface_id" && v == "true") { // interface-id is off by default on non-Dual-ToR, unless specified in config db
+                intf.is_interface_id = true;
+            }
         }
         vlans->push_back(intf);
     }
diff --git a/src/relay.cpp b/src/relay.cpp
index 5233fe5..f59253d 100644
--- a/src/relay.cpp
+++ b/src/relay.cpp
@@ -471,7 +471,10 @@ void relay_client(int sock, const uint8_t *msg, int32_t len, const ip6_hdr *ip_h
         option79.link_layer_type = htons(1);
         option79.option_code = htons(OPTION_CLIENT_LINKLAYER_ADDR);
         option79.option_length = htons(2 + 6); // link_layer_type field + address
-        
+
+        if ((unsigned)(current_buffer_position + sizeof(linklayer_addr_option) - buffer) > sizeof(buffer)) {
+            return;
+        }
         memcpy(current_buffer_position, &option79, sizeof(linklayer_addr_option));
         current_buffer_position += sizeof(linklayer_addr_option);
 
@@ -479,6 +482,19 @@ void relay_client(int sock, const uint8_t *msg, int32_t len, const ip6_hdr *ip_h
         current_buffer_position += sizeof(ether_hdr->ether_shost);
     }
 
+    if(config->is_interface_id) {
+        interface_id_option intf_id;
+        intf_id.option_code = htons(OPTION_INTERFACE_ID);
+        intf_id.option_length = htons(sizeof(in6_addr));
+        intf_id.interface_id = config->link_address.sin6_addr;
+
+        if ((unsigned)(current_buffer_position + sizeof(linklayer_addr_option) - buffer) > sizeof(buffer)) {
+            return;
+        }
+        memcpy(current_buffer_position, &intf_id, sizeof(interface_id_option));
+        current_buffer_position += sizeof(interface_id_option);
+    }
+
     auto dhcp_message_length = len;
     relay_forward(current_buffer_position, parse_dhcpv6_hdr(msg), dhcp_message_length);
     current_buffer_position += dhcp_message_length + sizeof(dhcpv6_option);
diff --git a/src/relay.h b/src/relay.h
index c5b0732..9f32a1d 100644
--- a/src/relay.h
+++ b/src/relay.h
@@ -21,6 +21,7 @@
 #define lengthof(A) (sizeof (A) / sizeof (A)[0])
 
 #define OPTION_RELAY_MSG 9
+#define OPTION_INTERFACE_ID 18
 #define OPTION_CLIENT_LINKLAYER_ADDR 79
 
 /* DHCPv6 message types */
@@ -55,6 +56,7 @@ struct relay_config {
     std::vector<std::string> servers;
     std::vector<sockaddr_in6> servers_sock;
     bool is_option_79;
+    bool is_interface_id;
 };
 
 
@@ -84,6 +86,12 @@ struct linklayer_addr_option  {
     uint16_t link_layer_type;
 };
 
+struct interface_id_option  {
+    uint16_t option_code;
+    uint16_t option_length;
+    in6_addr interface_id;  // to accomodate dual-tor, this opaque value is set to carry relay interface's global ipv6 address
+};
+
 /**
  * @code                sock_open(int ifindex, const struct sock_fprog *fprog);
  *