I have a mongo replica set of 3 nodes. We use the primary for both write and read. Its a legacy system so it doesn’t see much use. Mongo version used is 2.6.11 . When I run isMaster on one of the secondary nodes, this is the response I get.

{
    "setName" : "PROD DB",
    "setVersion" : 5,
    "ismaster" : false,
    "secondary" : false,
    "hosts" : [ 
        "xxxxxxxxxx:27017", 
        "xxxxxxxxxy:27017", 
        "xxxxxxxxz:27017"
    ],
    "primary" : "xxxxxxxxxx:27017",
    "me" : "xxxxxxxxxy:27017",
    "maxBsonObjectSize" : 16777216,
    "maxMessageSizeBytes" : 48000000,
    "maxWriteBatchSize" : 1000,
    "localTime" : ISODate("2024-08-01T04:10:16.843Z"),
    "maxWireVersion" : 2,
    "minWireVersion" : 0,
    "ok" : 1.0
}

Is the secondary working fine ? isMaster and secondary is both false.