IBD Networking: Tapping into undergrad vs MBA alma mater?

I'm seeing a lot of focus here placed on the size of the MBA program's network when selecting B-school. Out of curiosity is it weird to tap into your undergraduate network if where you went places decently on the Street? For example, I want to learn more about a particular bank/group but haven't had the best luck with alumni from the MBA program in which I'm currently enrolled. I do, however, see a decent number of folks from my undergraduate institution who have experience at said bank. How weird would it be to reach out to them? Would not utilizing your current MBA program's network be viewed odd (by prospective employers/students/alumni alike)? Same idea applies to graduates of the same university but who went to a different school - i.e. current Fuqua MBA student reaching out to a Duke undergraduate alumnus that holds an MBA from elsewhere, or who doesn't have one.