Duplicate ports

Lawh
Lawh Posts: 1

Hey!

I have an issue where I need to forward the same ports for multiple devices. I get an error for a duplicate port but the address these ports are forwarded to are different. I think this might be an error on the device, that it does not understand that multiple devices need to sometimes have the same ports forwarded.

Any help is appreciated, thanks!

All Replies

  • PeterUK
    PeterUK Posts: 3,326  Guru Member
    100 Answers 2500 Comments Friend Collector Seventh Anniversary
    edited June 20

    But you have to understand the limitation of NAT and only having one WAN IP for example a TCP port 88 is say forwarded to 192.168.0.88 and 192.168.0.99 both see the SYN and reply with SYN, ACK due to the protocol limitation both devices built up the connection causing the the other to fail not knowing which device you wanted to connect to.

    On high end firewalls you can do source IP NAT so the from x.x.x.x to 192.168.0.88 and the rest to 192.168.0.99 for the same port

    UDP has about the same problems unless the protocol for UDP is written to support it but no one has (that I know of) so port forwarding for UDP has the same limitation as TCP.

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