OpenVPN 2.5 & 2.6 rekeying

Honk

Honk

Member
I recently encountered a strange issue with OpenVPN 2.5 UDP on several servers. Instead of getting the following output every time the server does a rekeying like this
Code: 
2025-01-18 15:26:09 Initialization Sequence Completed
2025-01-18 16:21:40 VERIFY OK: depth=1, C=CH, ST=Zug, L=Zug, O=Perfect Privacy, CN=Perfect Privacy, emailAddress=admin@perfect-privacy.com
2025-01-18 16:21:40 VERIFY KU OK
2025-01-18 16:21:40 Validating certificate extended key usage
2025-01-18 16:21:40 ++ Certificate has EKU (str) TLS Web Server Authentication, expects TLS Web Server Authentication
2025-01-18 16:21:40 VERIFY EKU OK
2025-01-18 16:21:40 VERIFY OK: depth=0, C=CH, ST=Zug, O=Perfect Privacy, CN=Server_basel.perfect-privacy.com, emailAddress=admin@perfect-privacy.com
2025-01-18 16:21:40 WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1617', remote='link-mtu 1633'
2025-01-18 16:21:40 WARNING: 'keysize' is used inconsistently, local='keysize 128', remote='keysize 256'
2025-01-18 16:21:40 Outgoing Data Channel: Cipher 'AES-256-GCM' initialized with 256 bit key
2025-01-18 16:21:40 Incoming Data Channel: Cipher 'AES-256-GCM' initialized with 256 bit key
2025-01-18 16:21:40 Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, peer certificate: 4096 bit RSA, signature: RSA-SHA512

What I get instead is this, which seems a bit odd to me
Code: 
2025-01-20 16:21:28 Initialization Sequence Completed
2025-01-20 17:16:59 WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1617', remote='link-mtu 1633'
2025-01-20 17:16:59 WARNING: 'keysize' is used inconsistently, local='keysize 128', remote='keysize 256'

Please note that all of my OpenVPN 2.5 UDP configurations are the same, so it's not caused by a configuration error on the client side.

The following servers show this odd rekeying process so far:
Amsterdam1
Amsterdam3
Zurich2
Dusseldorf
London1
London2
Nuremberg2
Basel2
Frankfurt

I don't know if there are any ramifications to this, but I would like to get an answer as to why this is happening and what the possible ramifications are. I posted this in the Linux section, but I don't think it's a Linux specific issue, so it may apply to all operating systems.
 
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With OpenVPN 2.6 UDP, there is no rekeying process shown at all. However, there is a reneg-sec specified in the configuration files.

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I don't know if there are any ramifications to this, but I would like to get an answer as to why this is happening and what the possible ramifications are. I posted this in the Linux section, but I don't think it's a Linux specific issue, so it may apply to all operating systems.
 
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