How
to Do Port Forwarding To Multiple Devices on the Same Port
Title
You
may want to connect to multiple devices behind your Cradlepoint on the same
ports at times. This article describes how to configure port forwarding for
multiple devices or computers that need to use the same ports. Setting up port
forwarding to RDP (Port 3389) to multiple computers behind the same Cradlepoint
is a common use for this.
We
achieve this goal by configuring multiple port forward rules that look for
different internet ports but send traffic out on the same local ports.
Environment
Static
IP Address Cradlepoint Router
Multiple
devices that must be connected to the same port
Procedure
For
the sake of illustration, this procedure will describe how to configure RDP
(port 3389) to two different computers behind the same Cradlepoint.
- Creating
the 1st Rule
- Go
to Security>Zone Firewall>Port Forwarding and Proxy.
- Under
Port Forward Rules, click "Add."
- Identify
the rule.
- For
the Internet Ports, enter 3389 -> 3389.
- Enter
the IP address of the computer to which you want the first rule to forward
RDP traffic. Enter 3389 -> 3389 in the Local Ports field.
- As
the Protocol, select "TCP & UDP."
- Click
Save
Creating
the 2nd Rule
Under
Port Forward Rules, click "Add." Identify the rule. For the Internet
Ports, enter 3388 -> 3388. Enter the IP address of the computer to which you
want the second rule to forward RDP traffic. Put in Enter 3389 -> 3389 in
the Local Ports field. Click Save after selecting "TCP & UDP" as
the Protocol.
- Connecting
to the Computers
- Connect
to your Cradlepoint on port 3389 to connect to the first computer.
- Connect
to the Cradlepoint on port 3388 to connect to the second computer.
- For
both of these connections, once you reach the Cradlepoint, the local traffic
will be routed to port 3389. The internet port to which you connect (3389
or 3388) tells the Cradlepoint which computer to forward traffic to.
Further
Information
When
using port forwarding, the router examines the port on which incoming traffic arrives
and, if it matches a port forward rule, sends it to a specified IP address on
the specified local port. It will not work if you create two rules with the
same internet port. Because both rules will match, the Cradlepoint will have no
way of knowing which of the two computers to send traffic to.
We
work around this by configuring two rules with different internet ports but the
same local ports. To follow the example instructions, connect to the
Cradlepoint on port 3389, match with Rule 1 and go to that computer. Connecting
to the Cradlepoint on port 3388 would match Rule 2 and send you to the other
computer.
These
instructions do not apply only to RDP connections on port 3389. They can work
for any scenario where you need to forward to multiple devices on the same
port. The Cradlepoint will know which device to forward your traffic to as long
as you define different internet ports (but use the same local ports).
