varnish with plone

[eras mus]

Dear all,
i have plone zeoclients in ports 8081 and 8082. I ve configured with directors.
varnih is serving the pages only when 8081 is up . when it  is down
getting 503 error. in browser. it does the same for random as well as
round-robin.

http://pastebin.com/xrTbEuQR

it is fetching from only the first defined backend. when the first
backend is unhealthy nit getting output.