SEO Q: 2domain.com parked over 2domain.1domain.com pr effect

Hi all,

I guess this is an SEO question ... I have several casino related domains I want to host. I'm setup at a shared hosting server with an 'unlimited domains' package. When I went to add my 2nd domain to the server it turns out that it does the following:

username.primarydomain.com
and seconddomain.com was just parked over the 3rd level domain

when I type in seconddomain.com it seem to work normally, but how will this affect my ranking? Will it treat them all as the same domain? What does it mean for reciprocal links?

Wasn't sure where to post this...apologies if I'm in the wrong place, but I couldn't access the other forums.

Thanks,
CasinoLady