Using TortoiseCVS together with Eclipse
The Eclipse IDE has a built-in SSH client, activated in its CVS browser by using the "extssh" protocol string. It's functionally equivalent to using the "ext" protocol string, but eliminates the need for an external SSH client. This is fine when only Eclipse is used, but as Tortoise doesn't support the protocol, only its offline features will be available.
The official Eclipse documentation notes that "extssh" is incompatible with all other clients than Eclipse. The suggested solution is to configure "ext" to work in the same manner as "extssh" inside Eclipse, and then use "ext". See the link for details.
quelle: http://www.tortoisecvs.org/faq.html#eclipse