If there is more than one site hosted on a single IP, the client sends a request for the SSL certificate. In the "old" way, the client didn't say to which domain it wants to connect (it only told that after the SSL connection was established), so the server didn't know which certificate to send.
The problem has been solved with SNI, but it isn't universally supported (yet), though we are close (namely IE on XP). With SNI the client basically sends the server to which domain it wants to open a secure connection, so the server can serve the correct certificate.
If there is more than one site hosted on a single IP, the client sends a request for the SSL certificate. In the "old" way, the client didn't say to which domain it wants to connect (it only told that after the SSL connection was established), so the server didn't know which certificate to send.
The problem has been solved with SNI, but it isn't universally supported (yet), though we are close (namely IE on XP). With SNI the client basically sends the server to which domain it wants to open a secure connection, so the server can serve the correct certificate.