In the protocol, the client sends the maximum version that it supports, then the server chooses. Currently defined versions are 3.0, 3.1, 3.2 and 3.3 (SSL 3.1 is TLS 1.0, SSL 3.2 is TLS 1.1, and SSL 3.3 is TLS 1.2). This method of negotiating the protocol version assumes that the client supports a whole, continuous range of protocol versions, i.e. all versions from the beginning of times up to the one it indicates in its
ClientHello. There is no way, in standard SSL/TLS for the client to, for instance, say that it accepts TLS 1.0 and TLS 1.2 but not TLS 1.1.
Since the server merely states which version it will use, then the server is free in its support choices. When a server is "configured to support TLS 1.2", then it means that the server will support that protocol version, but it does not say whether it will support previous versions as well.
Usually, servers that "support TLS 1.2" are also able to use TLS 1.1 and TLS 1.0. Most of them also used to support SSL 3.0 but this support is disappearing because SSL 3.0 has an unfixable protocol flaw. A further trend is to look at TLS 1.0 with some suspicion (mainly due to the BEAST attack, though it does not work anymore) and some servers are beginning to cease to support it as well. Some even reject TLS 1.1 because they tolerate only the "GCM" cipher suites, that do not exist in TLS prior to TLS 1.2.