Who said anything about it being standard? I said I know this CAN happen, and I said it was quite some time ago. We can only hope this insanity isn’t still in practice anywhere, but I learned long ago that expecting a corporation to NOT do foolish things will give me the same disappointing results as expecting money to come out of my ass. If there’s a manager involved, then something on the tech side is going to get fucked up in the name of saving a buck. Therefore I cannot just assume OP gets a normal NAT address, nor can I assume they have any other firewall type device between them and the internet. With limited data, the best I can do is try and provide some general information, hopefully encourage them to ask more questions or provide more specific information, and just hope they don’t have a ridiculously stupid ISP that makes things needlessly complicated.
My best lens for capturing the sun and moon is a Canon EF 70-300mm f/4.5-5.6, which sounds like pretty much the same lens you have with a different mount? I found a Kenco doubler that doesn’t seem to produce any artifacts (this one goes on the back side of the lens) which has worked really well for grabbing sunspots. Wish I’d had more ambition to get out this Summer, there’s been a LOT of sunspot activity that I’ve missed.
On the other end I have a Sigma DC 17-70mm f2.8-4 which I’ve been using for model trains. I paid $233 for that one so it’s my most expensive, but getting a faster lens really helped with those low-light shots. Sometimes you find great deals, sometimes you find Chinese garbage. Luckily I never paid much for garbage.