dhcp-dns-update (nrcmd)			             dhcp-dns-update (nrcmd)


NAME
    dhcp-dns-update - Configures a DNS Update object for DHCP

SYNOPSIS
    dhcp-dns-update <name> create [<attribute>=<value>] 
    dhcp-dns-update <name> delete
    dhcp-dns-update list  
    dhcp-dns-update listnames
    dhcp-dns-update <name> show
    dhcp-dns-update <name> set <attribute>=<value> [<attribute>=<value> ...]
    dhcp-dns-update <name> get <attribute>
    dhcp-dns-update <name> unset <attribute>

    dhcp-dns-update <name> enable <attribute>
    dhcp-dns-update <name> disable <attribute>

DESCRIPTION
    The dhcp-dns-update command configures dynamic DNS update configurations
    for DHCP.  DHCP policies refer to this information to control the DNS 
    update behavior for each client.

EXAMPLES

STATUS

SEE ALSO
    policy

PROPERTIES
  Attributes:

    backup-server-addr[4] (AT_IPADDR, Optional, default: <none>)
        Specifies the backup DNS server address that receives DNS updates
        if the server specified in server-addr is down.

    backup-server-key[6] (AT_NAMEREF(Key), Optional, default: <none>)
        Specifies the TSIG key used to process all dynamic DNS updates for
        backup-server-addr.

    dns-host-bytes[14] (AT_RANGEINT(1-4), Optional, default: <none>)
        Sets the number of bytes in a lease IP address to use when forming
        in-addr.arpa names. The server forms names in the in-addr.arpa zone
        by prepending these bytes of the address (in reverse order) to the
        reverse zone name. If unset, the server synthesizes an appropriate
        value based on the scopes subnet size.

    dynamic-dns[9] (AT_ENUMBYTE(), Optional, default: update-all)
        Controls whether the DHCP server should attempt to update a
        DNS server with the name and address information from leases
        that are granted to requesting clients.

    force-dns-updates[16] (AT_BOOL, Optional, default: false)
        Determines whether the DHCP server retries a dynamic DNS update
        whenever a client renews its lease, even if DHCP thinks that the
        update has already been completed successfully.

    forward-zone-name[2] (AT_DNSNAME, Optional, default: <none>)
        Designates the DNS forward zone used to add a DHCP client host name
        (A record).

    host-name-generator[22] (AT_EXPR, Optional, default: <none>)
        Defines an expression that evaluates to the synthesized host name
        to be used. If undefined or the expression returns "<none>", the
        configured host name synthesis is used. If the expression returns
        a null value, no host name will be used.

    max-dns-ttl[17] (AT_TIME, Optional, default: <none>)
        Indicates the maximum number of seconds the DHCP server keeps DNS
        records it acquired through dynamic updates. Default is 86400s (1d).
        This value sets a ceiling (or time to live) on how long to keep
        DNS updates.
        When the DHCP server adds a DNS record, it uses a TTL of one
        third the lease time if it is between min-dns-ttl and
        max-dns-ttl values. If one third of the lease time is greater
        than max-dns-ttl, the TTL value is set to max-dns-ttl.

    min-dns-ttl[18] (AT_TIME, Optional, default: <none>)
        Indicates the minimum number of seconds the DHCP server keeps the
        DNS records acquired through dynamic updates. This value sets the
        shortest allowable time (or time to live) to keep DNS updates.
        When the DHCP server adds a DNS record, it uses a TTL of one
        third the lease time if it is  between min-dns-ttl and
        max-dns-ttl values. If one third of the lease time is smaller
        than min-dns-ttl, the TTL value will be set to min-dns-ttl.

    name[1] (AT_STRING, Required, default: <none>)
        Gives a unique name to the configuration object.

    reverse-zone-name[12] (AT_DNSNAME, Optional, default: <none>)
        Designates the DNS reverse (in-addr.arpa) zone that is updated
        with PTR records.
        If a reverse-zone-name is configured, DHCP always uses it.
        Alternately, if DHCP server synthesize-reverse-zone feature is
        enabled and if a reverse-zone-name is not configured, DHCP
        uses the lease IP address and the scope dns-host-bytes to
        automatically generate a reverse zone name.

    reverse-zone-prefix-length[20] (AT_RANGEINT(0-124), Optional, default: <none>)
        Identifies the prefix length of the reverse zone for ip6.arpa
        updates. The server forms the zone name using this value if
        configured; otherwise the prefix length is determined from the
        Prefix. This value must be a multiple of 4 as ip6.arpa zones are
        on 4 bit (nibble) boundaries. If not a multiple of 4, it is
        rounded up to the next higher multiple of 4.

    server-addr[3] (AT_IPADDR, Optional, default: <none>)
        Specifies the DNS server address that receives dynamic DNS updates.

    server-key[5] (AT_NAMEREF(Key), Optional, default: <none>)
        Specifies the TSIG key used to process all dynamic DNS updates for
        server-addr.

    synthesize-name[10] (AT_BOOL, Optional, default: disabled)
        Controls whether the DHCP server automatically creates DNS host
        names for DHCP clients that do not provide names. The server
        can synthesize unique names for clients based on the 'synthetic
        name stem' attribute.

    synthetic-name-stem[8] (AT_STRING, Optional, default: dhcp)
        Identifies the stem of the default host name to use if clients do not
        supply host names.

    update-dns-first[11] (AT_BOOL, Optional, default: disabled)
        Controls whether to update the DNS server before granting a lease.

    update-dns-for-bootp[13] (AT_BOOL, Optional, default: enabled)
        Controls whether the DNS server receives updates for BOOTP clients.
        If the server is replying to a BOOTP request, and is offering a
        lease configured to perform DNS updates, it checks
        this attribute before beginning the DNS update. This attribute allows
        an administrator to prevent DNS updates for BOOTP clients, while
        allowing updates for DHCP clients. If not configured, the server
        setting is used (which defaults to true).

    use-dns-update-prereqs[15] (AT_BOOL, Optional, default: true)
        If configured, the update ignores DHCP server level
        use-dns-update-prereqs. By default (enabled), the DHCP server
        adds prerequisites to DNS update messages to assure that the
        current client uses the domain name, before updating the client
        with the current lease (IP Address).
        If disabled, the DHCP server assumes that the current client is
        entitled to the domain name (and hence not add prerequisites to
        DNS update message) and associates the client's current lease
        with that domain name.
        Note: The DHCP server always adds prerequisites to the DNS
        update message while adding a new domain name record on behalf of
        a client acquiring a new lease and removing the domain name record
        when client release its lease or the lease expires.

    v6-host-name-generator[23] (AT_EXPR, Optional, default: <none>)
        Defines an expression that evaluates to the synthesized host name
        to be used. If undefined or the expression returns "<none>", the
        configured host name synthesis is used. If the expression returns
        a null value, no host name will be used.

    v6-synthetic-name-generator[19] (AT_ENUMINT(), Optional, default: hashed-duid)
        Controls what the DHCP server appends to the synthetic name stem
        when synthesizing the fully-qualified domain name for a client:
           duid
              The raw client DUID. This is formatted as a hexadecimal
              string with a hyphen as separator between each octet.
           hashed-duid
              The hashed client DUID. The rightmost 64-bits of the SHA-256
              hash over the client's DUID appended with the forward zone
              name (in DNS wire format) is used to generate a 13-character
              base 32 encoded string. This is the default method and the
              fallback method if the configured type is not possible
              (that is, the option needed to generate the selected type
              does not exist for the client).
           cablelabs-device-id
              The Cablelabs CL_OPTION_DEVICE_ID option data is used, if
              available. This is formatted as a hexadecimal string with a
              hyphen as separator between each octet. This might be used
              for names generated for DOCSIS 3.0 cable modems.
           cablelabs-cm-mac-addr
              The Cablelabs CL_CM_MAC_ADDR option data is used, if
              available. This is formatted as a hexadecimal string with
              a hyphen as separator between each octet. This might be
              used for names generated for CPEs behind a customer's
              DOCSIS 3.0 cable modem (if the customer has multiple CPEs,
              a name collision and disambiguation will likely result).
        Note: Several of these methods may cause privacy concerns if
        the DNS is accessible from the Internet.

