A domain name server implementing this specification is called a _DNS Seed_, and answers incoming DNS queries of type `A`, `AAAA`, or `SRV` as specified in RFCs 1035<sup>[1](#ref-1)</sup>, 3596<sup>[2](#ref-2)</sup> and 2782<sup>[3](#ref-3)</sup> respectively.
-`a`: address types, used to specify what address types should be returned for `SRV` queries. This is a bitfield that uses the types from [BOLT 7](07-routing-gossip.md) as bit index. This condition MAY only be used for `SRV` queries. (default value: 6, i.e., `2 || 4`, IPv4 and IPv6) [ FIXME: BOLT 7 says that IPv4 and IPv6 are address descriptor types 1 & 2. Are we missing something in this description? ]
-`l`: `node_id`, the bech32-encoded `node_id` of a specific node, used to ask for a single node instead of a random selection. (default: null)
-`n`: the number of desired reply records (default: 25)
If the DNS seed does not implement filtering by a given condition it MAY ignore the condition altogether (i.e., the seed filtering is best effort only).
Queries distinguish between _wildcard_ queries and _node_ queries, depending on whether the `l`-key is set or not.
Upon receiving a wildcard query, the DNS seed MUST select a random subset of up to `n` IPv4 or IPv6 addresses of nodes that are listening for incoming connections.
For `A` and `AAAA` queries, only nodes listening on the default port 9735, as defined in [BOLT 01](01-messaging.md), MUST be returned.
The results are serialized in a reply with a query type matching the client's query type, i.e., `A` queries result in `A` replies, `AAAA` queries result in `AAAA` replies, and `SRV` queries result in `SRV` replies, but they may be augmented with additional records (e.g., to add `A` or `AAAA` records matching the returned `SRV` records).
The DNS seed MAY additionally return the corresponding `A` and `AAAA` records that indicate the IP address for the `SRV` entries in the Extra section of the reply.
Due to the large size of the resulting reply, the reply may be dropped by intermediate resolvers, hence the DNS seed MAY omit these additional records upon detecting a repeated query.
In accordance with the Bitcoin DNS Seed policy<sup>[4](#ref-4)</sup>, replies to random queries (i.e. queries to the seed root domain and to the `_nodes._tcp.` alias for `SRV` queries) MUST be random samples from the set of all known good nodes and MUST NOT be biased.
