# dns-update > Sends one dynamic DNS update (RFC 2136), signed with a TSIG hmac-md5 key, to the authoritative DNS server of a zone, and points a name in the zone at an IPv4 address. The update replaces the A records of the name.... ----------- ## tool/dns-update **Type:** Command Sends one dynamic DNS update (RFC 2136), signed with a TSIG hmac-md5 key, to the authoritative DNS server of a zone, and points a name in the zone at an IPv4 address. The update replaces the A records of the name. The command prints nothing when the server accepts the update. See [DNS update](../../diagnostics-monitoring-and-troubleshooting/dynamic-dns). IPv4 address of the DNS server that is authoritative for `zone`. The update goes to its TCP port 53. DNS zone that holds the name, for example `example.com`. Name to update, relative to `zone`: `name=office` with `zone=example.com` updates `office.example.com`. A full name is added to the zone again, and a name with a trailing dot fails with `failure: bad name`. IPv4 address for the A record of the name. Required. Only one address is accepted (`failure: only one address allowed`), and IPv6 addresses are refused. Name of the TSIG key, as configured on the DNS server. Without `key-name` and `key`, the update is sent unsigned. Secret of the TSIG key in base64, as configured on the DNS server. The algorithm is hmac-md5. Put the value in quotes, because a base64 value can end in `=`. Time to live of the record, in seconds. For an address that changes, use a short value such as `300`. Default: 86400.