This  SLB method provide a list of unrecognized headers. In this group method, the list of headers is searched for one whose name matches <header_name>. If the header is found, the header value is mapped to an arbitrary real service in the group. This mapping is persistent, so the same header value will correspond to the same real service every time. Note that header_name must be a non-standard HTTP header. In otherwords, "Host", "User-Agent", etc. cannot be used. Note also that the CLI will not enforce this restriction, so the user can enter "Host" as the <header_name> argument and the CLI will not
complain. The group lookup will fail every time, though.

slb group method <group_name> hh header_name [rr|sr|lc] [threshold]

header_name - header name parameter that is a non-standard HTTP header

[rr|sr|lc] - argument can be called the "first choice method". If a client request does not yet have an assigned real
service, this method will be used to choose a real service for that client, based on the request
properties appropriate to the group method.

[threshold] - argument only applies if the "first choice method" is lc, and is the same as the group method lc threshold parameter.