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DNS issue after a short period - SSL VPN

Hi,

I have a user using SSL VPN (Remote Access) to connect to the office.

This worked good over the last months, but we're now having strange issues:

After a short ( but undefined) period of time, he's unable to access any internal web resources using DNS names.

For example, he connects and can access welcome.ihw.local, but after a moment, he's not longer able to access it using DNS, but only using its IP.

When he's having the issue, I can do nslookup and this works fine, but ping is not working.

When he reboots his machine, both nslookup and ping are working.

If he disconnects the VPN, and reconnects, that's not working neither.

He needs to restart his workstation to fix the issue, and then after a few minutes, it's the same scenario again.

Could you please help?

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0 Erick Jan over 2 years ago

Hi Thomas,

Thank you for reaching out to Sophos Community.

Have you tried to use any how-to videos, documentation, Sophos Assistant, or KBA to try to check the issue?

Also, Can we verify that there’s only one Machine/user affected?

Have you tried to use a different device for the affected user ?

Can you try the problematic user account to a working device who have no issues with the VPN.

Erick Jan
Community Support Engineer | Sophos Technical Support
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0 Vivek Jagad over 2 years ago

Hello Thomasb74 ,

Thank you for reaching out to the community, can you please share the following:

1.) Screenshot of the Global SSL VPN Settings
2.) Screenshot of the route print output from the client machine [when working after the restart]
3.) Screenshot of the route print output from the client machine [when not working]
4.) Monitor traffic using Packet Capture Utility [working and non-working] : https://support.sophos.com/support/s/article/KB-000035761?language=en_US

Thanks & Regards,
_______________________________________________________________

Vivek Jagad | Team Lead, Global Support & Services

Sophos Community | Product Documentation | Sophos Techvids | SMS
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0 Thomasb74 over 2 years ago in reply to Erick Jan

Hi Erick,
I reviewed the complete configuration and unfortunately found nothing suspicious that could cause this issue.

I use the same SSL VPN and it works like a charm, with absolutely 0 issue.

I cannot use a different device for that, as it's my manager computer at home, and also I cannot try his account on my computer as he's in UK and I'm not... I compared the .ovpn file with mine, as the file is exactly the same.

From the Sophos logs, I cannot find anything happening at that time, so I'm more and more wondering if that can be a bug in SFOS, causing this weird behavior..
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0 Thomasb74 over 2 years ago in reply to Vivek Jagad

Hi Vivek,

Here's the Global SSL VPN settings:

I'll get the route print (working/non-working) and the Packet Capture and I'll get back to you soon.

Thanks
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0 Erick Jan over 2 years ago in reply to Thomasb74

Hi Thomas,

Is it possible to create a test account(with the same config) and send it to test on your manager's computer?

Erick Jan
Community Support Engineer | Sophos Technical Support
Sophos Support Videos | Product Documentation | @SophosSupport | Sign up for SMS Alerts
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0 Thomasb74 over 2 years ago in reply to Vivek Jagad

Dear Vivek, I made a first capture. but how can I export it from the GUI? I used WinSCP to connect to the XG310, but can only find a pktcap_hex.dump, which cannot be opened in WireShark..

Thanks !
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0 Vivek Jagad over 2 years ago in reply to Thomasb74

You can opt for the following - Create and download a packet capture : https://support.sophos.com/support/s/article/KB-000037007?language=en_US Thomasb74

Thanks & Regards,
_______________________________________________________________

Vivek Jagad | Team Lead, Global Support & Services

Sophos Community | Product Documentation | Sophos Techvids | SMS
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