RTRR from 2 QNAP's on same router

[Bob Zelin]

Hi -
I think I answered my own question, but I thought I would ask for confirmation.
I have two QNAP's on the same network. I have a UPnP router (Synology RT2600ac). If I have both QNAP's on, and RTRR in Hybrid Backup Sync is set for Port 8899 (the default) -
It seems that when I go into "Apply to Router" in MyQnapCloud to tell the router to port forward 8899 to the QNAP's - it will either do one or the other, but not both.
Even if I manually do this on the router (type in the IP address to assign to) - when I do a test, it will fail on one of the 2 QNAPs. If I simply turn off UPnP on the router, so all the port
forwarding from the QNAP #1 disappears, and now I switch to QNAP # 2 and "Apply to Router" - the second QNAP now works correctly, and I can see the QNAP # 2 IP address and forwarding of 8899
in the Port Forwarding menu.

SO - same question - can you only assign ONE QNAP to the router at port 8899 for RTRR ? And if I wanted to have two QNAPs on the second network, should I just make QNAP # 2 at a different port (like 8898) ?

Thanks -
I know this seems self explanatory, but I just wanted to check with someone with more experience than I have. Both QNAP's are running latest QTS 4.3.4 OS (the July firmware).

Bob Zelin

[Mousetick]

can you only assign ONE QNAP to the router at port 8899 for RTRR ?

Yes. Only one destination host on the network per TCP port.

And if I wanted to have two QNAPs on the second network, should I just make QNAP # 2 at a different port (like 8898) ?

Yes.

Note: This is not specific to QNAP nor RTRR. It's just how port-forwarding works on NAT routers. Since all the devices behind the NAT router share the same public IP address, the router relies on the port number to direct incoming traffic to specific devices on the local network. So it's the same principle if you were to host 2 web servers on 2 separate machines for example, behind the same NAT router. You'd have to use different ports for each web server (e.g. 80 and 81).

[Don]

You can only forward a port on a router to a single IP/port. As you guessed you need to use different ports. I would also not use uPnP as it presents a security risk. Any program could forward any port it wanted to.

[Bob Zelin]

thank you for the confirmation !
You guys are great.

Bob Zelin