From iris.conf:
# IDENT STRING: A fixed string to use as an ident on IRC.
# See ident setting documentation.
ident_string: webchat

# WEBIRC MODE: This option controls how the IP/hostname of the
# connecting browser will be sent to IRC. If set, the IRC server may
# be able to transparently display users of Iris as from their
# original hosts, rather than as coming from the webclient's IP.
# Possible values include:
# - "webirc": Use WEBIRC type blocks, with an IRCD configuration of
#   the following style:
#
   cgiirc: {
     type webirc;
     hostname <127.0.0.1>;
     password <spectrum>;
   };
#
#   You must set webirc_password to be the same as <password>.
#
# - "realname": Disables WEBIRC.
#   Sends the IP and hostname in the realname field in the format
#   <hostname>/<ip> - <normal realname>, convenient for human reading.
#
# - <left empty>: Disables WEBIRC.
#   Sends the IP in the realname field, overriding the REALNAME option.
webirc_mode:      webirc

# WEBIRC PASSWORD: Used for webirc mode "webirc", see webirc_mode option
# documentation.
webirc_password: spectrum

From ircd.conf

auth {
    /* user: webirc@IP.OF.YOUR.WEBIRC . the webirc@ part is required */
    user = "webirc@127.0.0.1";

    /* password: password the webirc client sends in the WEBIRC command.
     * You can use a encrypted password here (see above auth block).
     */
    password = "spectrum";

    /* spoof: This is required to keep it what it is currently if you
     * want the webirc client to show the users' real host as their
     * host on IRC.
     */
    spoof = "webirc.";
    class = "users";
};