Все ж в мануале написано... server_host (default: localhost)
The name of the host running the LDAP server, e.g.
server_host = ldap.example.com
Depending on the LDAP client library you're using,
it should be possible to specify multiple servers
here, with the library trying them in order should
the first one fail. It should also be possible to
give each server in the list a different port
(overriding server_port below), by naming them like
server_host = ldap.example.com:1444
With OpenLDAP, a (list of) LDAP URLs can be used to
specify both the hostname(s) and the port(s):
server_host = ldap://ldap.example.com:1444
ldap://ldap2.example.com:1444
All LDAP URLs accepted by the OpenLDAP library are
supported, including connections over UNIX domain
sockets, and LDAP SSL (the last one provided that
OpenLDAP was compiled with support for SSL):
server_host = ldapi://%2Fsome%2Fpath
ldaps://ldap.example.com:636