Challenge / Response to Prevent Replay Attack - Using nonce as challenge
In general symmetric ciphers are not vulnerable to attacks with known plaintext. So in general it is perfectly possible to encrypt the previous nonce. 

With multiple nodes it would be a good idea to include the identity of the sender / receiver in the challenge or at least in the poly 1305 based authentication. Otherwise an attacker may trick a node into authenticating a different node than intended.