SSL peer certificate validation failed:self signed certificate

[arsene...@gmail.com]

I test to setup mongodb with the following scenario:

1 router

3 configdb

3 shard

Installation for those processes (router, configdb, shard) works fine without error. For instance

mongos --configdb cfg1:1234,cfg2:1234,cfg3:1234 --logpath /path/to/log.file

mongod --fork --configsvr --dbpath /path/to/db --logpath /path/to/log.file --port 1234

mongod --fork --dbpath /path/to/db --logpath /path/to/log.file --port 4321

But mongo routers can't be started up when ssl parameters are enabled 

mongos ... --sslMode requireSSL --sslPEMKeyFile mongodb.pem --sslCAFile ca.pem 

mongod --configsvr ... --sslMode requireSSL --sslPEMKeyFile mongodb.pem --sslCAFile ca.pem 

mongod ... --sslMode  requireSSL --sslPEMKeyFile mongodb.pem --sslCAFile ca.pem

The router (mongos) throws error as following:

... SSL peer certificate validation failed:self signed certificate

... couldn't check dbhash on config server cfg:1234 :: caused by :: 9001 socket exception

The log in configdb shows 'SSL peer certificate validation failed:self signed certificate' error. 

It seems to me the ca/ pem files, but don't know how to troubleshooting this. Any hints or places from which I can start?

Thanks