Secury printing application Uniflow, stops working under VPN when my dsl is broken

Question

I have a very strange problem with a Canon printing system called Uniflow under VPN. The whole system works perfectly, but when there is a break in my adsl or I reset the router of the internet provider. The system stops working, the problem is that my server is unable to register the printer in my delegation. To get it working again I have to configure the printer of my delegation with another ip and re-register with my server. I've talked to the manufacturer that is Canon and he says it has to be a problem with my firewall blocking something. I have done a lot of tests among them I have restarted the two firewalls, but I do not understand where the problem may be. Any ideas?

Toshi_Esumi · Answer

Is ADSL's pppoe terminated at FGT? My guess is something to do with sessions. When sessions inside of FGT were taken down due to a break, applications need to re-establish TCP sessions so that FGT can set up new sessions up to keep track of them. If uniFLOW's applications don't detect the break on either the cloud side or local side, they assume the same source/destination ports can communicate each other, especially out-to-in direction, which doesn't come through FGT any more. Many applications, ex. Citrix, which expect FW's existence on the network path, have keep-alive&checking mechanism to detect connection down and avoid timeout.

Since you can re-create the problem constantly, I would suggest you open a ticket with TAC and get it analyzed.

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