Round Robin A Records

[Gary McAfee/Raleigh/IBM]

>> If we lose one of the servers, say it is booted down, every second
>> request will be the IP address of the unavailable server.

>Yes. In most case, it is handles with a load balancing proxy, or some nice
>nifty routing that handles the case of a fallout.

Do you happen to have any IBM S/390s in your shop?  If DNS is running on
one of these, it will not hand out the IP addresses belonging to a downed
server or host.  The application of interest must be running on an S/390.

>> Does anyone know a way of configuring DNS so that if one server is down
>> all requests are directed to the available server dynamically? Manually
>> we remove the A record for the unavailable server.

>I don't know if that is possible.

Sounds like you're talking about a non-DNS server (like a web server).
Again, this is done for you if DNS is running on an IBM S/390.  The
function is referred to as DNS/WLM (or Connection Optimization).  Not only
does it direct requests away from downed servers, but it does true load
balancing based on the current system capacity of the available hosts in
the sysplex.  If one if bogged down with work, requests will be directed
away from that host to one that has more capacity.  Again, the applications
must be running on an S/390.

Gary McAfee
IBM z/OS Communications Server Development


Igmar Palsenberg <maillist at chello.nl>@isc.org on 10/19/2000 08:48:05 AM

Sent by:  bind-users-bounce at isc.org


To:   Steve Ford <sford at ncc.dhl.com>
cc:   bind-users at isc.org
Subject:  Re: Round Robin A Records




On Thu, 19 Oct 2000, Steve Ford wrote:

> Can someone please advise:
>
> We have two web servers mirrored. We have setup DNS (BIND 4.9.7) like
> this to round robin the requests:
>
> www    0300    IN A    198.141.222.111
>             0300    IN A    198.141.223.117
>
> When a client attempts to resolve the address of the hostname 'www' is
> it true that the client will receive one of the IP addresses on a round
> robin basis?
>
> If we lose one of the servers, say it is booted down, every second
> request will be the IP address of the unavailable server.

Yes. In most case, it is handles with a load balancing proxy, or some nice
nifty routing that handles the case of a fallout.

> Does anyone know a way of configuring DNS so that if one server is down
> all requests are directed to the available server dynamically? Manually
> we remove the A record for the unavailable server.

I don't know if that is possible.

>
> Regards,
> Steve


     Igmar