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Joined: Sat Dec 29, 2018 1:36 am

Mikrotik 9100 port forwarding problem

Sat Dec 29, 2018 1:46 am

Hello community,
I did not find any solutions to solve really strange port-forwarding problem in my network. Probably somebody here knows the right way to solve it.

My network:
I have 2 Router-cascade with DMZ-zone.
The first router has a DSL-modem function and a connection for the USB-Printer (IP-pool aa.aa.aa.0/24). USB- Printer can work with TCP/IP and 9100 port RAW. (aa.aa.aa.1 port 9100).

One LAN cable connects the first port with Mikrotik 2011 (WAN connection on Mikrotik).
Mikrotik has two networks with gateway and with gateway). All computers and routers have static IP's.
NAT rules: masquerade from Mikrotik networks to WAN interface and few DST-NAT rules for the Storage drive in the network from the DMZ side. Everything works fine, I have internet connection can ping the first router aa.aa.aa.1 can use a web server and so on.

At the same time I can not print any documents with standard winprint function by windows 7. It seems, that my PC (IP can not get a response from the first router with connected printer (aa.aa.aa.1 port 9100). I tried everything, checked traffic with Wireshark and Torch, made additional DST-Nat rules from the first router to the PC nothing helps.
Strange behavior:
If I connect my PC to the first router directly, print something and after that will connect my PC to Mikrotik again- everything will work properly and I can print everything even without DST-NAT rules. After PC reboot it does not print again.

What I ve recognized:
-The first router see only the Mikrotik IP address.
-Torch did not show me any direct connections from PC to the First Router. Only PC- external IP address from Mikrotik.
-WINPRINT uses each time a different port from 20000-65000 pool (wireshark info).

I tried everything, with firewall rules for established connection and without. Nothing helps.
Probably, somebody here knows this strange behavior and can help me.

Kindly regards and Happy New Year,

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