MongoDB 3.6 introduced the concept of a seed list that is specified using DNS records, specifically SRV and TXT records. The use of SRV records eliminates the requirement for every client to pass in a complete set of state information for the cluster. Instead, a single SRV record identifies all the nodes associated with the cluster (and their port numbers) and an associated TXT record defines the options for the URI.

Without the SRV configuration the Client must list several nodes along with the ssl and replicaSet options when connecting. This allows a client to connect to a replica set even if one of the nodes that the client specifies is unavailable.

The Host field does not support SRV records. Parsing of Authentication Connection String field fails for mongodb+srv format in the URI.

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