DNS Cache

[sdip]

Hi,

We have configured SQUID proxy in two HP boxes, also we have configured a URL in our 3DNS box.

When we are pointing to that 3DNS URL then everything is working fine. If one server SQUID process is down then it is pointing to other server.

Now we have configured CNAME in our DNS server where we have pointed to 3DNS URL. When we do nslookup it is showing alternate server IP in every 5 seconds, but if any client access that CNAME & connect to one server & in case that server SQUID process gets down then it could not forwarded that request to other server. Though nslookup perfectly show other server IP but users can't access from their browser.

We have checked users PC & there also nslookup is working fine.

Is it DNS caching issues ?

[Geoff Wild]

Found this on Google - might help you:

Client-side caching does not break round-robin DNS. It only gives that *appearance*

Sure, an individual client will continue to hit the same server untill the cached A-record record TTL expires.

Then it will do a fresh query to DNS and it will get whatever server is next in line.

Also, different clients will hit and cache different servers.

The round-robin function still works.

There's not normally a reason to force a fresh lookup for every name resolution attempt from one client, is there?

Here's a quote from an article:

Windows contains a client-side Domain Name System (DNS) cache.
The client-side DNS caching may generate a *false impression* that DNS "round robin" is not taking place from the DNS server to the Windows client. Pinging the same A-record domain name may result in the client using the same IP address. This behavior is different from previous Microsoft operating systems

However, if you really want to do this:

How to Disable Client-Side DNS Caching in Windows
http://support.microsoft.com/default.aspx?scid=kb;en-us;245437

seems to work for XP too.


Rgds...Geoff

[Thomas Bianco]

you might consider Network Load Balancing clustering. i'm not familiar enough with squid to say if it's stateless, but i would assume since HTTP is, squid must be.

i think Network Load Balancing clustering is the right term in HPUX, someone check me?