round-robin question

[Chris Thompson]

On Oct 30 2008, Bryan Irvine wrote:

>On Thu, Oct 30, 2008 at 10:50 AM, Matthew Pounsett <matt at conundrum.com> wrote:
>>
>> On 30-Oct-2008, at 13:34 , Bryan Irvine wrote:
>>
>>> Creative I must admit, but doesn't work.  Is there another way to get
>>> this working perhaps with?
>>
>> Even if you can get BIND to hand out more than one identical record (I
>> wouldn't expect that to work), the balance of load is dependant on the
>> clients' algorithms for choosing an A record.. and the clients may not do
>> what you want or expect.  Some clients are semi-random, some rotate through
>> the A records they get, and some cache and keep the first one they pick.
>
>Yeah but is it even possible to give more than one identical record?

You can specify them in the zone file, but duplicates are removed when
BIND reads them, so it's quite useless. You can't get BIND to return 
duplicate RRs in response to a query.

>> I don't believe there's any reliable way to do this kind of traffic
>> engineering with DNS.  If you need to shift load around in very specific
>> ways, then you should look at actual load balancing hardware/software to do
>> the job.
>
>Yeah he really does need a real load balancer.  He's just trying this
>as a temporary solution.

We always refer to this as "poor man's load balancing".

-- 
Chris Thompson
Email: cet1 at cam.ac.uk