Hi!

I use Cisco Anyconnect VPN to connect to where I work. It connects normally, but after a few seconds, I can't connect to almost any of our internal systems. I thought it was an internal problem, but we've been trying to figure this out for weeks and just couldn't find the problem. All we know is, the VPN only works properly when I replace my router with something else. I used my phone's 4G and everything worked perfectly. I also connected the optical fiber converter directly to my laptop and authenticated via PPPoE on my machine and it worked. I tried replacing my router with a TL-WR702N and it worked too.

I replaced my C1200 with another C1200 and the issue continued, so we made the PPPoE authentication in the optical fiber converter and used my router only as a repeater and the issue continued. When I connected the ethernet cable from my laptop directly at the converter, it worked.

We already checked everything, including MTU, DNS, route, firewall and everything we could think of.

I also tried debugging with my ISP's tech support and nothing.

PS: I went to update my router's firmware, but it's already the latest version: https://www.tp-link.com/br/support/download/archer-c5-w/

Does anyone know if this is a bug? How can we debug it to be sure?

Thank you in advance.