> Looking a way to bind IPs to specific upstream.
> Like load balancing to work for new IPs only.
> Like known clients sent to upstream used at their first connection.
>
> Any ideas?

You should check ip_hash directive:
http://wiki.nginx.org/NginxHttpUpstreamModule#ip_hash

Best regards,
Piotr Sikora < piotr.sikora@frickle.com >