I have an offsite Microsoft IIS FTPS host (x.74), listening on port 8443. IIS Version 6.2 build 9200, Windows server 2012 R2.
From my workstation, i can telnet x.74:8443. (workstation -> site 1 firewall -> host)
A service provider cannot telnet the same port. (NAT x.12:8443) (provider -> site 2 firewall -> site 1 firewall -> host)
both sites are company controlled and on the same WAN. service provider is stationed at site 2. NAT rule is at site 2. We can see the traffic on both site firewalls with appropriate source and destination, and traffic is accepted. So issue is most likely on server itself.
IIS logs on server do not show any attempts from ServiceProvider, but i can see my attempts. i've turned off server firewall and uninstalled antivirus to eliminate possible sources of block. we've tried adding NAT address to IIS site binding alongside physical server IP.
Would there be something i need to tweak on IIS (or elsewhere) to enable ServiceProvider to access the port?
Extra info: Most configurations were cloned from an identical server that communicates with the same ServiceProvider. need to shift service provider to site 2 due to shared services something something. (provider -> host) this configuration is working perfectly. no NAT. FTPS will be passive mode.