code: def extend_hosting_port_info(self, context, port_db, hosting_device,
                                   hosting_info):
          
          if hosting_info.get('segmentation_id') is None:
              LOG.debug('No segmentation ID in hosting_info -- assigning')
              hosting_info['segmentation_id'] = (
                  port_db.hosting_info.get('segmentation_id'))
          is_external = (port_db.device_owner == DEVICE_OWNER_ROUTER_GW)
          hosting_info['physical_interface'] = self._get_interface_info(
              hosting_device['id'], port_db.network_id, is_external)
          ext_dict, net = self._get_external_network_dict(context, port_db)
          if is_external and ext_dict:
              hosting_info['network_name'] = ext_dict['network_name']
              hosting_info['cidr_exposed'] = ext_dict['cidr_exposed']
              hosting_info['gateway_ip'] = ext_dict['gateway_ip']
              details = self.get_vrf_context(context,
                                             port_db['device_id'], port_db)
              router_id = port_db.device_id
              router = self.l3_plugin.get_router(context, router_id)
              # skip routers not created by the user -- they will have
              # empty-string tenant IDs
              if router.get(ROUTER_ROLE_ATTR):
                  return
              hosting_info['vrf_id'] = details['vrf_id']
              if ext_dict.get('global_config'):
                  hosting_info['global_config'] = (
                      ext_dict['global_config'])
              self._add_snat_info(context, router, net, hosting_info)
          else:
              if ext_dict.get('interface_config'):
                  hosting_info['interface_config'] = ext_dict['interface_config']
docs: Get the segmenetation ID and interface
  
          This extends the hosting info attribute with the segmentation ID
          and physical interface used on the external router to connect to
          the ACI fabric. The segmentation ID should have been set already
          by the call to allocate_hosting_port, but if it's not present, use
          the value from the port resource.