WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1606', remote='link-mtu 1634'

mistral55

May 13 07:39:28 ovpn-client1[14184]: WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1606', remote='link-mtu 1634'
May 13 07:39:28 ovpn-client1[14184]: WARNING: 'tun-mtu' is used inconsistently, local='tun-mtu 1504', remote='tun-mtu 1532'

somebody said:

Re: Annoying warning
Post by janjust » Tue May 31, 2011 3:06 pm

this warning is there for a reason: remove
CODE: SELECT ALL

tun-mtu-extra 32
from your client config and reconnect.

my question, what does tun-mtu-extra 32, and why should I remove it, it's there for a reason.

TinCanTech

mistral55 wrote my question, what does tun-mtu-extra 32, and why should I remove it, it's there for a reason.

If you don't know what it does then what is your reason to use it ?

mistral55

It was placed while installing NordVPN on my router, and by looking for that warning I came across someone with the same problem and told you to remove it, but I want to know why, and what does it do?

mistral55

And that's not all, I started looking because the internet got very slow and found this error too:

May 13 08:11:05 ovpn-client1 [14184]: AEAD Decrypt error: bad packet ID (may be a replay): [# 3948695] - see the man page entry for --no-replay and --replay- window for more info or silence this warning with --mute-replay-warnings

For this I would have to lower the MTU but then I still have the same notification.

So I bought an Asus RT-AC88U to install the VPN on the router, but it has not worked so far.

TinCanTech

TinCanTech wrote
mistral55 wrote my question, what does tun-mtu-extra 32, and why should I remove it, it's there for a reason.
If you don't know what it does then what is your reason to use it ?

mistral55 wrote I came across someone with the same problem and told you to remove it, but I want to know why, and what does it do?

See --tun-mtu-extra in the manual and then remove it.

mistral55 wrote found this error too:

May 13 08:11:05 ovpn-client1 [14184]: AEAD Decrypt error: bad packet ID (may be a replay): [# 3948695] - see the man page entry for --no-replay and --replay- window for more info or silence this warning with --mute-replay-warnings

For this I would have to lower the MTU

This has nothing to do with MTU.

mistral55

OK, any idea what causes that AEAD Decrypt error ?

TinCanTech

mistral55 wrote May 13 08:11:05 ovpn-client1 [14184]: AEAD Decrypt error: bad packet ID (may be a replay): [# 3948695] - see the man page entry for --no-replay and --replay- window for more info or silence this warning with --mute-replay-warnings

mistral55

Sorry, but I don't know which manual you mean.

TinCanTech

Google have been searching the internet for you since 1998.

mistral55

NordVPN said it is not possible on a Asus RT-AC88U:

The downside to OpenVPN is that in its current architecture, it is not scalable. It runs as a monolithic process and cannot run multi-threaded.

This means that if you have a beefy processor with 8 cores and each of the core has 8 threads, OpenVPN will use only a single thread in one of the available cores.

Regarding routers - they do not have powerful CPUs, thus encrypting and decrypting OpenVPN traffic is a real challenge for them. For that reason, the speed can drop by a large amount.

You could try increasing your speed by connecting to a few different servers (preferably to the ones in yours or neighbouring country), changing between TCP and UDP, enabling QoS and changing Upload and Download to 100Mbps, disabling SPI Firewall and NAT Acceleration (if your router has one). You could also try looking for the most optimal MTU value on your router which could be in the range from 1300 to 1500.

If these changes do not help and you are getting better speeds while connected to the same servers with our software on your computer, then, unfortunately, your router's hardware cannot encrypt the internet traffic fast enough and this is the reason for speed drop. In this case, there is nothing that I can suggest you, unfortunately.

mistral55

TinCanTech wrote Google have been searching the internet for you since 1998.

I googled it and therefore lowered the tun-mtu to 1472 and lowered the mssfix to 1432, and then I saw that tun-mtu-extra 32 and wondered what that was for. But lowering that tun-mtu and mssfix didn't help, so I know how to google, but it didn't help.

TinCanTech

Are you using this for your own VPN server ? Or are you trying to connect to NordVPN ?

mistral55

TinCanTech wrote Are you using this for your own VPN server ? Or are you trying to connect to NordVPN ?

Yes, I have a subscription with NordVPN, and I specially bought the Asus RC-AC88U because you can install a VPN on it.