Using the OFTP V1 over X.25 or over X.25 over ISDN requires a router to bridge the TCP and X.25 networks. Both transports have been tested with Funkwerk router models R4300 and X8500.
The following table lists required firewall exceptions for X.25.
| Description | Source | Destination | 
| Control connection | All  | All routers, TCP port 146. | 
| Monitoring connection | All  | All routers, UDP port 161 (unless changed). | 
| Inbound data connection | All routers. | All trading engine hosts, one port per embedded server using X.25. | 
All instances of Activator must be able to connect to every ISDN router on its remote CAPI port (2662 by default). No reverse or call-back connection is made, as with X.25.
For the CAPI service connection for X.25 over ISDN: