OK SOLVED! First of all I configured the AS400 with its proper Public IP 87.x.x.248
On Endian:
- Added 87.x.x.248 as alias in network interfaces
- Added new Destination NAT rule under Port Forward-NAT
- Source: Any Uplink
- Destination: Uplink Main/87.x.x.248
- Allow: Without IPS
- Protocol: Custom - TCP
- Ports: 23 & 449
- NAT: do NAT
- Traslate into IP: 10.x.0.100
Source NAT: no rules
Incoming Routed Traffic: no rules
System Access: default rules
Interzone Firewall: default rules
That's all.
It didn't worked on the fly, after these updates I didn't connect yet, but in minutes everything went up and the AS400 was there.
All attempts to connect to are logged as I requested.
Then I turned back on my HTTP proxy (SQUID) for content filtering and SNORT for intrusion detection.
For future reference, I did a PrintScreen of all setup pages and a backup of working configuration.
I want to thank mrkroket for his kind help, and hope this could be useful for someone else.
Faber