address pools

load balancing:

nat on dc0 from any to $extip ->
    { 10.0.0.1, 10.0.0.2 } round-robin

stateful IDS balancing:

pass in on dc0
    dup-to { ($IDSif $IDS_ip1),
    ($IDSif $IDS_ip2) } round-robin
    from any to $dmz keep state