I have set up my mongod instance with the following config:

  port: 27017
    mode: requireSSL
    PEMKeyFile: /config/mongo.pem
    CAFile: /config/ca.pem
    allowConnectionsWithoutCertificates: true

  authorization: enabled

I can connect to it fine with mongosh:

mongosh --host="<mydomain.com>:27017" --username="root" --db="mydbname" --ssl --authenticationDatabase="admin"

But when I try to connect with mongodump using the exact same options...:

mongodump --host="<mydomain.com>:27017" --username="root" --db="mydbname" --ssl --authenticationDatabase="admin"

...It fails with the message Failed: error connecting to db server: no reachable servers. Checking the mongod logs I see the following:

{"t":{"$date":"2023-12-08T13:55:30.966+00:00"},"s":"I",  "c":"NETWORK",  "id":22943,   "ctx":"listener","msg":"Connection accepted","attr":{"remote":"<my ip address>","uuid":"41542a35-0815-4fb7-a618-d3ecf6b21a33","connectionId":244,"connectionCount":4}}
{"t":{"$date":"2023-12-08T13:55:30.980+00:00"},"s":"W",  "c":"NETWORK",  "id":23234,   "ctx":"conn244","msg":"No SSL certificate provided by peer"}
{"t":{"$date":"2023-12-08T13:55:30.985+00:00"},"s":"I",  "c":"NETWORK",  "id":22944,   "ctx":"conn244","msg":"Connection ended","attr":{"remote":"<my ip address>","uuid":"41542a35-0815-4fb7-a618-d3ecf6b21a33","connectionId":244,"connectionCount":3}}

These three lines are repeated several times until the connection times out.

I'm wondering why it says No SSL certificate provided by peer when I have allowConnectionsWithoutCertificates set to true. It obviously doesn't seem to be a problem when using mongosh as it connects without a problem.

2 Answers 2


Parameter CAFile is pointless in your config, because you don't provide any client certificate (and that's the reason why you need allowConnectionsWithoutCertificates: true). Instead it might be required in mongosh and/or mongodump

mongosh --host="<mydomain.com>:27017" --username="root" --db="mydbname" --tlsCAFile=/config/ca.pem --tls --authenticationDatabase="admin"

No SSL certificate provided by peer is just a warning.

mongosh provides option --tlsUseSystemCA which does not exist in mongodump. Maybe try connection string:

mongodump --uri="mongodb://root:password<mydomain.com>:27017?authSource=admin&tls=true&tlsCAFile=/config/ca.pem"

mongosh "mongodb://root:password<mydomain.com>:27017?authSource=admin&tls=true" --tlsUseSystemCA

Maybe have a look at How Security in MongoDB works - which is a bit more advanced.

  • I found the solution, posted answer. Due to my mistake of not noticing a line in the log saying the client driver is outdated. Although I wish the server would log the different lines with clear tags in the beginning [ERROR/WARNING/INFO etc.]. Would make it easier. I didn't realize CAFile was only for client certificate verification. Good to know, then I can remove it. Thanks!
    – taxfree
    Dec 9, 2023 at 11:32

Figured out the problem. It was due to an outdated version of mongodump.

As I checked the server logs I saw that there was actually one line near the beginning (which I had previously missed) that was different among the repeated ones:

"Received wire protocol op code or command that is no longer supported. The client driver may require an upgrade. For more details see https://dochub.mongodb.org/core/legacy-opcode-removal"

That's when I went to check the mongodump version using mongodump --version and I got the output

mongodump version: built-without-version-string

It was from an outdated mongo-tools package so I uninstalled it with dpkg -P mongo-tools (I'm using OS Ubuntu 20.04) and then followed the instructions on Installing the Database Tools on Linux to install the newer mongodb-database-tools.

Obviously the instructions are gonna different depending on OS/System and which version you want to install, but these were the commands for me:

wget https://fastdl.mongodb.org/tools/db/mongodb-database-tools-ubuntu2004-x86_64-100.9.4.deb
sudo apt install ./mongodb-database-tools-ubuntu2004-x86_64-100.9.4.deb

After getting the latest version of mongodump, it all works.

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