схема базы данных OVN_Northbound  (OVN_Northbound database schema)
  
DHCP_Options TABLE
OVN implements native DHCPv4 support which caters to the common
       use case of providing an IPv4 address to a booting instance by
       providing stateless replies to DHCPv4 requests based on
       statically configured address mappings. To do this it allows a
       short list of DHCPv4 options to be configured and applied at each
       compute host running ovn-controller.
       OVN also implements native DHCPv6 support which provides
       stateless replies to DHCPv6 requests.
   Summary:
       cidr                          string
       DHCPv4 options:
         Mandatory DHCPv4 options:
            options : server_id      optional string
            options : server_mac     optional string
            options : lease_time     optional string, containing an
                                     integer, in range 0 to
                                     4,294,967,295
         IPv4 DHCP Options:
            options : router         optional string
            options : netmask        optional string
            options : dns_server     optional string
            options : log_server     optional string
            options : lpr_server     optional string
            options : swap_server    optional string
            options : policy_filter  optional string
            options : router_solicitation
                                     optional string
            options : nis_server     optional string
            options : ntp_server     optional string
            options : tftp_server    optional string
            options : classless_static_route
                                     optional string
            options : ms_classless_static_route
                                     optional string
         Boolean DHCP Options:
            options : ip_forward_enable
                                     optional string, either 0 or 1
            options : router_discovery
                                     optional string, either 0 or 1
            options : ethernet_encap optional string, either 0 or 1
         Integer DHCP Options:
            options : default_ttl    optional string, containing an
                                     integer, in range 0 to 255
            options : tcp_ttl        optional string, containing an
                                     integer, in range 0 to 255
            options : mtu            optional string, containing an
                                     integer, in range 68 to 65,535
            options : T1             optional string, containing an
                                     integer, in range 68 to
                                     4,294,967,295
            options : T2             optional string, containing an
                                     integer, in range 68 to
                                     4,294,967,295
         String DHCP Options:
            options : wpad           optional string
            options : bootfile_name  optional string
            options : path_prefix    optional string
            options : tftp_server_address
                                     optional string
            options : domain_name    optional string
       DHCPv6 options:
         Mandatory DHCPv6 options:
            options : server_id      optional string
         IPv6 DHCPv6 options:
            options : dns_server     optional string
         String DHCPv6 options:
            options : domain_search  optional string
            options : dhcpv6_stateless
                                     optional string
       Common Columns:
         external_ids                map of string-string pairs
   Details:
       cidr: string
              The DHCPv4/DHCPv6 options will be included if the logical
              port has its IP address in this cidr.
     DHCPv4 options:
       The CMS should define the set of DHCPv4 options as key/value
       pairs in the options column of this table. For ovn-controller to
       include these DHCPv4 options, the dhcpv4_options of
       Logical_Switch_Port should refer to an entry in this table.
     Mandatory DHCPv4 options:
       The following options must be defined.
       options : server_id: optional string
              The IP address for the DHCP server to use. This should be
              in the subnet of the offered IP. This is also included in
              the DHCP offer as option 54, ``server identifier.''
       options : server_mac: optional string
              The Ethernet address for the DHCP server to use.
       options : lease_time: optional string, containing an integer, in
       range 0 to 4,294,967,295
              The offered lease time in seconds,
              The DHCPv4 option code for this option is 51.
     IPv4 DHCP Options:
       Below are the supported DHCPv4 options whose values are an IPv4
       address, e.g. 192.168.1.1. Some options accept multiple IPv4
       addresses enclosed within curly braces, e.g. {192.168.1.2,
       192.168.1.3}. Please refer to RFC 2132 for more details on DHCPv4
       options and their codes.
       options : router: optional string
              The IP address of a gateway for the client to use. This
              should be in the subnet of the offered IP. The DHCPv4
              option code for this option is 3.
       options : netmask: optional string
              The DHCPv4 option code for this option is 1.
       options : dns_server: optional string
              The DHCPv4 option code for this option is 6.
       options : log_server: optional string
              The DHCPv4 option code for this option is 7.
       options : lpr_server: optional string
              The DHCPv4 option code for this option is 9.
       options : swap_server: optional string
              The DHCPv4 option code for this option is 16.
       options : policy_filter: optional string
              The DHCPv4 option code for this option is 21.
       options : router_solicitation: optional string
              The DHCPv4 option code for this option is 32.
       options : nis_server: optional string
              The DHCPv4 option code for this option is 41.
       options : ntp_server: optional string
              The DHCPv4 option code for this option is 42.
       options : tftp_server: optional string
              The DHCPv4 option code for this option is 66.
       options : classless_static_route: optional string
              The DHCPv4 option code for this option is 121.
              This option can contain one or more static routes, each of
              which consists of a destination descriptor and the IP
              address of the router that should be used to reach that
              destination. Please see RFC 3442 for more details.
              Example: {30.0.0.0/24,10.0.0.10, 0.0.0.0/0,10.0.0.1}
       options : ms_classless_static_route: optional string
              The DHCPv4 option code for this option is 249. This option
              is similar to classless_static_route supported by
              Microsoft Windows DHCPv4 clients.
     Boolean DHCP Options:
       These options accept a Boolean value, expressed as 0 for false or
       1 for true.
       options : ip_forward_enable: optional string, either 0 or 1
              The DHCPv4 option code for this option is 19.
       options : router_discovery: optional string, either 0 or 1
              The DHCPv4 option code for this option is 31.
       options : ethernet_encap: optional string, either 0 or 1
              The DHCPv4 option code for this option is 36.
     Integer DHCP Options:
       These options accept a nonnegative integer value.
       options : default_ttl: optional string, containing an integer, in
       range 0 to 255
              The DHCPv4 option code for this option is 23.
       options : tcp_ttl: optional string, containing an integer, in
       range 0 to 255
              The DHCPv4 option code for this option is 37.
       options : mtu: optional string, containing an integer, in range
       68 to 65,535
              The DHCPv4 option code for this option is 26.
       options : T1: optional string, containing an integer, in range 68
       to 4,294,967,295
              This specifies the time interval from address assignment
              until the client begins trying to renew its address. The
              DHCPv4 option code for this option is 58.
       options : T2: optional string, containing an integer, in range 68
       to 4,294,967,295
              This specifies the time interval from address assignment
              until the client begins trying to rebind its address. The
              DHCPv4 option code for this option is 59.
     String DHCP Options:
       These options accept a string value.
       options : wpad: optional string
              The DHCPv4 option code for this option is 252. This option
              is used as part of web proxy auto discovery to provide a
              URL for a web proxy.
       options : bootfile_name: optional string
              The DHCPv4 option code for this option is 67. This option
              is used to identify a bootfile.
       options : path_prefix: optional string
              The DHCPv4 option code for this option is 210. In
              PXELINUX' case this option is used to set a common path
              prefix, instead of deriving it from the bootfile name.
       options : tftp_server_address: optional string
              The DHCPv4 option code for this option is 150. The option
              contains one or more IPv4 addresses that the client MAY
              use. This option is Cisco proprietary, the IEEE standard
              that matches with this requirement is option 66
              (tftp_server).
       options : domain_name: optional string
              The DHCPv4 option code for this option is 15. This option
              specifies the domain name that client should use when
              resolving hostnames via the Domain Name System.
     DHCPv6 options:
       OVN also implements native DHCPv6 support. The CMS should define
       the set of DHCPv6 options as key/value pairs. The define DHCPv6
       options will be included in the DHCPv6 response to the DHCPv6
       Solicit/Request/Confirm packet from the logical ports having the
       IPv6 addresses in the cidr.
     Mandatory DHCPv6 options:
       The following options must be defined.
       options : server_id: optional string
              The Ethernet address for the DHCP server to use. This is
              also included in the DHCPv6 reply as option 2, ``Server
              Identifier'' to carry a DUID identifying a server between
              a client and a server. ovn-controller defines DUID based
              on Link-layer Address [DUID-LL].
     IPv6 DHCPv6 options:
       Below are the supported DHCPv6 options whose values are an IPv6
       address, e.g. aef0::4. Some options accept multiple IPv6
       addresses enclosed within curly braces, e.g. {aef0::4, aef0::5}.
       Please refer to RFC 3315 for more details on DHCPv6 options and
       their codes.
       options : dns_server: optional string
              The DHCPv6 option code for this option is 23. This option
              specifies the DNS servers that the VM should use.
     String DHCPv6 options:
       These options accept string values.
       options : domain_search: optional string
              The DHCPv6 option code for this option is 24. This option
              specifies the domain search list the client should use to
              resolve hostnames with DNS.
              Example: "ovn.org".
       options : dhcpv6_stateless: optional string
              This option specifies the OVN native DHCPv6 will work in
              stateless mode, which means OVN native DHCPv6 will not
              offer IPv6 addresses for VM/VIF ports, but only reply
              other configurations, such as DNS and domain search list.
              When setting this option with string value "true", VM/VIF
              will configure IPv6 addresses by stateless way. Default
              value for this option is false.
     Common Columns:
       external_ids: map of string-string pairs
              See External IDs at the beginning of this document.