Yeah it probably is, at least it's safe to say that the issue is with starhub and nothing to do with nintendo, routers settings etc. Probably will switch ISP as well, 2 years and the problem has not been fixed or looked into. Well done Starhub.
I'm using Starhub Fibre 200 plan, and using the 868L router. I have no issues with Internet connectivity on my 3DS XL (Black). I have Pokemon X&Y, ORAS and MH4U. All games and eshop are fine when connecting to the net.
I'm not sure if it's your console setting or something else. Just my 2-cents.
Could we get an official response and support from starhub reguarding this issue? Connection works through a US proxy so im pretty sure the problem is on starhub's side. Seems like only certain places are affected though.
Just to share, somehow I was able to fix 003-2101 issue after removing the SafeSurf VAS entirely from My Account. It took about 1 or 2 days to take effect.
I am using DLink router, previous used WPA2 causes the same problem (somehow Dlink WPA2 doesn't work properly), so I change to WEP and everything working fine now.