Just wanted chime in and say that the dd-wrt way works flawlessly,(using linksys wrt54g v2) currently at school but does anyone know if you can access the pokemon event for ruby/sapphire even with these ports blocked? I'll try once I get back if nobody knows and report back with findings.
Same here the DD-WRT tutorial works great for me. I have a 2DS and have to use the browser gateway thing. So this is really helpful. If I ever had to download a game update on emunand I just wait till I get into emunand remove the blocked addresses in my router and click apply settings. Then add them again after the update is finished. FYI I don't seem to have to reset the router to block and unblock these addresses just apply and it works.
As for Pokemon I can't say for sure but after I updated my pokemon Y game I was able to connect online in my game while the 3DS update/shop addresses were blocked. I didn't battle or trade or anything I just wanted to see if it would let me in and it did.