What are the steps to problem solve when all I can get are 503s?

[Jacques]

I am trying to use Varnish on OpenSolaris.  Due the help of others, I have
versions compiling and not crashing that are based on three different
versions of Varnish.

I'm using 4516, 2.1.2 with the 649 patch, and trunk.   I've also tried
compiling with gcc 4.3.3 in addition to the OpenSolaris standard of 3.4.3.
 That changed nothing.

All compiled copies of varnish seem to start just fine.  I can use
varnishlog and see my requests arriving at Varnish.

However, responses are always 503 with " FetchError: no backend connection".
 Using tcpdump, I see no calls to the backend server from Varnish, ever.

For simplicity, I'm using the basic start of:

varnishd -a :80 -b 87.238.47.204:80

What are right steps to determine what is wrong?  I see nothing in syslogs.
 Varnish doesn't complain.  Using all the same steps on ubuntu, I get
exactly what I expect, a cached version of the backend server.

Any pointers about how I should figure out what is failing would be helpful.

Thanks,
Jacques

I've also noticed that the cache is starting at 500GB.  Changing the cache
size to 512MB didn't have any impact on the 503s.
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