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Home » GFI User Forums » Kerio Control » Kerio VPN error - udp traffic is probably blocked
Kerio VPN error - udp traffic is probably blocked [message #147122] Mon, 25 November 2019 12:43 Go to next message
febsystems is currently offline  febsystems
Messages: 3
Registered: May 2019
Hi everyone, I've a Kerio Control (update at last release 9.3.2. build 3557) and VPN service correctly configured no problema in connecting from remote but from 2-3 days I can't connect witch VPN, i get error "udp traffic is probably blocked". I've try from different location and with differente PC but nothing. I don't changed nothing in Kerio Control on in our office but VPN stop working some days ago.
From the log I view user logging in VPN but 10 seconds later peer closed connection.

Any ideas??

Thank you in advance.
Re: Kerio VPN error - udp traffic is probably blocked [message #147126 is a reply to message #147122] Tue, 26 November 2019 05:22 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
I have been having the same issue for a few weeks now, was working and then suddenly not. My ISP claims they are not blocking any ports (despite me being the only one with connection issues) and we've made no configuration changes.
Both Kerio box and vpn software updated tonight to the latest version. Win10Pro
I have searched online and the scant results have yielded no solutions. GFI seems to be amazingly not interested.
Log file attached

thanks,
Justin
  • Attachment: debug.log
    (Size: 77.77KB, Downloaded 378 times)
Re: Kerio VPN error - udp traffic is probably blocked [message #147129 is a reply to message #147126] Tue, 26 November 2019 14:46 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
I also wanted to add that I tested with a different laptop and got the same error which leads me to think it's some configuration change my ISP recently made.
If so, what would I ask them after they've already said they're not blocking any ports?
Re: Kerio VPN error - udp traffic is probably blocked [message #147306 is a reply to message #147122] Fri, 20 December 2019 13:38 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
I doubt this is the only solution
Re: Kerio VPN error - udp traffic is probably blocked [message #147307 is a reply to message #147129] Fri, 20 December 2019 13:46 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
I also took the same laptop offsite and was able to connect through another network so it would appear the issue is indeed with my ISP.

What's interesting is that I seem to connect for a moment before Kerio kicks me off.
Any ideas as to what settings within Kerio or my ISP's setup could be causing this?

How about some holiday spirit here folks? hehe

thanks!
Re: Kerio VPN error - udp traffic is probably blocked [message #147319 is a reply to message #147307] Tue, 24 December 2019 18:34 Go to previous messageGo to next message
billybob is currently offline  billybob
Messages: 35
Registered: October 2018
Your ISP is blocking UDP traffic and that is why the client is failing. Looking at your debug logs, your connection is successful during tcp session but fails when the secret is transmitted during the udp session. They are probably using udp for performance reasons but the client should be able to switch to tcp only. Wish they had a simple toggle switch that would allow tcp traffic only to work around situations like yours.
Happy Holidays

[Updated on: Tue, 24 December 2019 18:36]

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Re: Kerio VPN error - udp traffic is probably blocked [message #147333 is a reply to message #147319] Thu, 02 January 2020 20:54 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
Thank you for the reply!!!!!
I am back in contact with my ISP and hopefully working through the issue with them.

Re: Kerio VPN error - udp traffic is probably blocked [message #147334 is a reply to message #147319] Thu, 02 January 2020 21:05 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
billybob wrote on Tue, 24 December 2019 12:34
Your ISP is blocking UDP traffic and that is why the client is failing. Looking at your debug logs, your connection is successful during tcp session but fails when the secret is transmitted during the udp session. They are probably using udp for performance reasons but the client should be able to switch to tcp only. Wish they had a simple toggle switch that would allow tcp traffic only to work around situations like yours.
Happy Holidays
by THEY do you mean Kerio or my ISP?

Again, my ISP claims they are not blocking any ports.

thanks
Re: Kerio VPN error - udp traffic is probably blocked [message #147389 is a reply to message #147334] Sun, 12 January 2020 17:28 Go to previous messageGo to next message
monkeymissile is currently offline  monkeymissile
Messages: 54
Registered: January 2005
can anyone clarify which ports Kerio uses for VPN? Certainly 8080 and 4090, but are there any others?

thanks!
Re: Kerio VPN error - udp traffic is probably blocked [message #147444 is a reply to message #147122] Wed, 22 January 2020 14:34 Go to previous messageGo to next message
michael012 is currently offline  michael012
Messages: 1
Registered: January 2020
febsystems wrote on Mon, 25 November 2019 12:43
Hi everyone, I've a Kerio Control (update at last release 9.3.2. build 3557) and VPN service correctly configured no problema in connecting from remote but from 2-3 days I can't connect witch VPN, i get error "udp traffic is probably blocked". I've try from different location and with differente PC but nothing. I don't changed nothing in Kerio Control on in our office but VPN stop working some days ago.
From the log I view user logging in VPN but 10 seconds later peer closed connection.

Any ideas??

Thank you in advance.
Did you try changing the protocol? Secondly which VPN are you using? My suggestion would be that try a different protocol and if that doesn't work, then go for dedicated IP VPN because dynamic IP address might be causing problems.
Re: Kerio VPN error - udp traffic is probably blocked [message #147455 is a reply to message #147389] Fri, 24 January 2020 19:42 Go to previous messageGo to next message
billybob is currently offline  billybob
Messages: 35
Registered: October 2018
monkeymissile wrote on Thu, 02 January 2020 21:05
billybob wrote on Tue, 24 December 2019 12:34
Your ISP is blocking UDP traffic and that is why the client is failing. Looking at your debug logs, your connection is successful during tcp session but fails when the secret is transmitted during the udp session. They are probably using udp for performance reasons but the client should be able to switch to tcp only. Wish they had a simple toggle switch that would allow tcp traffic only to work around situations like yours.
Happy Holidays
by THEY do you mean Kerio or my ISP?

Again, my ISP claims they are not blocking any ports.

thanks
They is kerio in my post (sorry for the confusion). You will probably have to download some kind of software and test udp ping to make sure your ISP is telling the truth.


monkeymissile wrote on Sun, 12 January 2020 17:28
can anyone clarify which ports Kerio uses for VPN? Certainly 8080 and 4090, but are there any others?

thanks!
They use port 4090 tcp/udp for vpn.

[Updated on: Fri, 24 January 2020 19:43]

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Re: Kerio VPN error - udp traffic is probably blocked [message #151134 is a reply to message #147306] Mon, 21 February 2022 08:55 Go to previous messageGo to next message
molave is currently offline  molave
Messages: 2
Registered: February 2022
Hello,

I'm having the same issue as yours, were you able to find the solution for this?

it will be a great help. Laughing

Thanks
Re: Kerio VPN error - udp traffic is probably blocked [message #151140 is a reply to message #151134] Mon, 21 February 2022 16:02 Go to previous messageGo to next message
JimmyKeen is currently offline  JimmyKeen
Messages: 3
Registered: July 2021
molave wrote on Mon, 21 February 2022 08:55
Hello,

I'm having the same issue as yours, were you able to find the solution for this?

it will be a great help. Laughing

Thanks
Did you try changing the protocol? Secondly which VPN are you using? My suggestion would be that try a different protocol and if that doesn't work, then go for dedicated IP VPN because dynamic IP address might be causing problems.


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Re: Kerio VPN error - udp traffic is probably blocked [message #152140 is a reply to message #151140] Mon, 04 July 2022 21:30 Go to previous message
vigor is currently offline  vigor
Messages: 7
Registered: June 2005
Hi all,

having examined this with 2 different ISP's I can confirm that problem is not on the ISP side (they are not blocking UDP 4090 traffic).
The problem is that particular client is behind NAT/proxy due to inadequate public IP's available. This happens more often on mobile networks. When particular client (same dynamic IP, everything is the same - no reconfiguration) just moved to public (IP) on ISP side and Kerio VPN client instantly works completely and stable.
"Dirty solution" is to use IPsec client (built in in Windows OS) for connecting to the Control VPN site. For some reason IPsec works behind NAT flawlessly.
Unfortunately, Kerio VPN driver have no MTU setting. Probably if MTU value can be lowered we could test values that are working. This problem is more often and related exclusively and only Kerio VPN.

Kind regards,

V'ger


V'ger A.K.A. CrNi
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