If you are using IP masquerading or NAT, oidentd can optionally return a username for connections from other machines. Support for this is specified by calling oidentd with the -m (or --masq) flag and by creating an /usr/local/etc/oidentd_masq.conf file.
oidentd can also forward requests for an IP masqueraded connection to the machine from which connection originates by way of the -f option. This will only work if the host to which the connection is forwarded is running oidentd with the -P (proxy) flag, or if the hosts ident daemon will return a valid reply regardless of the input supplied by and the address of the host requesting the info (some ident daemons for windows do this, maybe others).
<IP Address|Hostname>[/<Mask>] <Ident Response> <System Type>
The first field contains the IP address or the hostname of a machine that IP masquerades through the machine on which oidentd runs. The mask parameter can be either a network mask or a mask in CIDR notation. A mask of 24 is equivalent to 255.255.255.0, a mask of 16 is equivalent to 255.255.0.0, etc.
The second field specifies the reply that oidentd will return for lookups to the host matching the IP address specified in the first parameter.
The third field specifies the operating system the machine matching the first parameter is running.