Legacy iRule generating constant error logs

Hi

Matchclass or class match are used to compare against Data Groups but I don't see one defined in your code and the error being returned indicates the same. Therefore, try this

when CLIENT_ACCEPTED {
  # Check if the client IP address is a node in the VIP's default pool and active
  if {[IP::client_addr] equals [active_nodes -list [LB::server pool]]}{
   # log local0. "SNAT'ing for [IP::client_addr], member of pool [LB::server pool]"
   snat automap
  }
}