Load balancing clients based on client domain name

You might be able to use [NAME::lookup] against the reverse zone, but keep in mind that not all reverse zones accurately reflect the domain from which the user is connecting. (ISPs frequently retain control over the reverse zones, and refuse to customize, returning always records reflecting some-ISP-specific-infrastructure-based-string+the ISPs own domain name.)

You'd have to have a reliable, low-latency resolver configured on LTM to perform the lookup, and DNS timeouts are relatively long if no response from the authoritative nameserver, so you might have to experiment with VS timeout values to accomodate that possibility.

If those are not insurmountable barriers, something like this might do the trick:

when HTTP_REQUEST {
  set PTRname [getfield [IP::client_addr] "." 4].[getfield [IP::client_addr] "." 3].[getfield [IP::client_addr] "." 2].[getfield [IP::client_addr] "." 1].in-addr.arpa.
  set clDomain [domain [NAME::lookup $PTRname] 2]
  switch $clDomain {
    "x.com" { pool x.com }
    "y.com" { pool y.com }
    "z.com" { pool z.com }
  }
}

HTH

/deb