positive and negative dns values

Hi,

Our squid configuration is having problems access a site which uses dynamic
ip addresses for their servers ( redundancy) . The DNS ttl the site uses is
0 which means that all queries are forced back to their authorative DNS
server.

THE FAQ refers to how to get true DNS TTL into Squid's ip cache but I don't
really want to implement this fix unless it's really necessary.

Could someone please explain in a bit more detail how squid uses the
positive and negative dns ttl values.

If a server is successfully running and connecting to a host on a
particular IP address (eg 1.1.1.1) and the address changes to 1.1.1.2 does
the negative_dns_ttl tag force the cache to reexamine the IP address after
it's cache expiry or does the IP address remain in Squid's ip cache until
the positive_dns_ttl expires ?

My current setting are
# TAG: negative_ttl time-units
# Time-to-Live (TTL) for failed requests. Certain types of
# failures (such as "connection refused" and "404 Not Found") are
# negatively-cached for a configurable amount of time. The
# default is 5 minutes. Note that this is different from
# negative caching of DNS lookups.
#
negative_ttl 5 minutes

# TAG: positive_dns_ttl time-units
# Time-to-Live (TTL) for positive caching of successful DNS lookups.
# Default is 6 hours (360 minutes). If you want to minimize the
# use of Squid's ipcache, set this to 1, not 0.
#
positive_dns_ttl 1 hours

# TAG: negative_dns_ttl time-units
# Time-to-Live (TTL) for negative caching of failed DNS lookups.
#
negative_dns_ttl 5 minutes

Thanks in advance

Mark Bizzell
Received on Tue Mar 28 2000 - 23:51:51 MST