Forwarding a port on my Max

Something seems odd. I have forwarded ports on many routers over the past 25 years and this one has me scratching my head. When I look to setup forwarding under port forwarding, the cellular side defaults but when I check my external address its a address. My sim is T-Mobile. I am not using a VPN. When I try to telnet from outside to my specified port its not open using either of the two addresses above. I am not sure where that 28 address is coming from, my assumption was that’s the address the cell modem is currently using. But that would normally show up as my external address. Is T-Mobile doing something odd?

I suspect they are doing something quite common in a unique way. That is Carrier Grade NAT.

Most Mobile networks route cellular internet traffic via a central NAT/firewall appliance. This blocks inbound traffic. However when CGNAT is used the IP allocated to the router should be in the subnet so your IP starting 28 is weird. Are you sure you’re not using a VPN anywhere?

GRS-DOD is the registered ISP for your IP - does that mean anything to you?

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Nope, never heard of that. I sometimes run a vpn on a sandbox for testing things. But not on production boxes. I will chalk it up to t-mobile and find another solution. I was going to setup an ftp server in my motorhome to bring over large files from the homestead. But I am starting to look into file syncing software after seeing this issue. Thanks, -Bill

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It seems you are in a DoD address space (Minutes before Trump left office, millions of the Pentagon’s dormant IP addresses sprang to life) which is, of course, quite intriguing.

Aside from that, if the objective is to achieve access to your behind-the-router devices then a FusionHub with a public IP address (hosted by UpCloud or vultr, for instance) with a SpeedFusion connection to your router would be one way to go. @MartinLangmaid has provided extensive material assisting in setting that up (see for instance VPN from Peplink behind Cellular NAT to Home on dynamic IP - #2 by MartinLangmaid).