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

Kristian Lyngstol kristian at
Wed May 18 12:08:11 CEST 2011


On Tue, May 17, 2011 at 10:09:45AM -0700, d1+varnish at wrote:
> my question is -- what to do with Varnish config, and, ultimately, *its*
> apache backend(s)?
> is it sufficient to keep one varnish instance listening only on IPv4 to
> both of nginx's ingress AddressFamilies, passed via a single/common
> proxypass?
> or, do i need separate Varnish instances/listeners, one for each
> AddressFamilty -- effectively setting up a parallel path for IPv4 or
> IPv6 traffic?

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.

- Kristian

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