Dual Vanity Sink Clog

[williwyo]

I have two single vanity sinks in my bathroom that share a main drain and vent, both in the wall. When I run the water in one sink, the other sink fills. When I try to snake the drain, the auger runs from one sink drain line through to the other and never diverts down the main drain. Any advice on how to clear this?

Thanks for your help!