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Date:      Mon, 8 Jul 2024 08:17:06 +0200
From:      Andrea Venturoli <ml@netfence.it>
To:        "Patrick M. Hausen" <hausen@punkt.de>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   Re: OpenVPN suddenly working one way only
Message-ID:  <44769ec1-7523-49c7-a64d-181530c90a0d@netfence.it>
In-Reply-To: <AC8533A8-F877-4934-8907-6532C44D9CF7@punkt.de>
References:  <202407061502.466F28cR033040@gndrsh.dnsmgr.net> <dd0115c5-f07b-4f3c-8158-ed2594011890@netfence.it> <AC8533A8-F877-4934-8907-6532C44D9CF7@punkt.de>

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On 7/6/24 18:13, Patrick M. Hausen wrote:

Hello.


>> It's almost surely due to a problem with the UDP packets that implement the VPN: again, according to tcpdump they go out host B, but never reach host A.
> 
> Is it remotely possible that one of the ISPs blocks these UDP packets as part
> of an automatic "DoS protection" mechanism?

Of course I cannot exclude it with 100% confidence.

That said:
_ host A has about 10 VPNs, only one is misbehaving, so I guess it's not 
ISP A;
_ host B has an enterprise-grade contract, so they should not firewall 
anything; another one of the above VPNs connects to a different host 
which has the same type of contract with the same ISP and it works.

Maybe it's the ISP or someone in between... I have no control over this.
I'd like to exclude any local issue, about which I might actually do 
something.

  bye & Thanks
	av.



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