does Varnish (between nginx frontend and apache backend) need separate instances/listeners for IPv4/6 dual-stack use?

d1+varnish at d1+varnish at
Wed May 18 17:13:05 CEST 2011


On Wed, 18 May 2011 12:08 +0200, "Kristian Lyngstol"
<kristian at> wrote:
> Varnish will listen to both IPv4 and IPv6 if available. It will also
> talk to backends using both ipv4 and ipv6. It currently prefers ipv4 for
> backend communication if the supplied hostname resolves to both ipv4 and
> ipv6, which is configurable via the prefer_ipv6 param.
> Varnish more or less Just Works with IPv6.

I understand that Varnish CAN listen at ipv4/ipv6.  I'm still unclear as
to what SHOULD be done in this stack.

Are you suggesting that this is sufficient?

  server {
    listen @ both IPv4 & IPv6
    location / {
      proxypass http://varnish_IPv4_listener
 varnish listening ONLY on IPv4 (launched as ... -a <IPv4>:port1 -T
 <IPv4>:port2 ...)
 drupal/apache backends listening ONLY on IPv4


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