Access same value with one of multiple keys in c++?

I need a way to access a value by passing in any key that the value could have. For example, a player object that can be accessed by either their ip address or name?

To illustrate.

Player1 has ["a", "1.2.3.4"] Player2 has ["b", "3.4.5.6"] Player3 has ["c", "2.2.9.3"]

So, to access Player2 I could use players["b"], or players["3.4.5.6"]

Should I just iterate over a vector for that? But I plan to have anywhere around 100 elements, so would a tree-like container be better than an array list?

Could you use std::multimap for that? Or even in std::map?