On Fri, 15 Feb 2008, Peter Bowyer wrote:
> On 15/02/2008, Brent Clark <brentgclarklist@???> wrote:
> >
> > I have a fair amount of users hamering my internal smtp server / and
> > also would be great for redundancy. I would like to know. Would it be
> > ok to just add another machine and then to just update the DNS to
> > handle the round robin effect.
>
> Does 'internal' mean these are MSA clients? I wouldn't like to rely on
> any given MUA's behaviour when faced with 2 IPs, especially when one
> of them doesn't work. Test and test again before you roll it out.
We use round robin DNS and it works fine, so long as nothing breaks :-)
Most MUAs will not try more than one IP address, so if the IP address they
have fixed on stops working they will break too. The way we deal with this
is to just shift the IP addresses of the broken machine onto a hot spare.
(We haven't automated it because our machines are too reliable to make it
worth adding complexity.) The other problem is that client computers often
don't respect the TTL on DNS records, so they may not respect changes
promptly. (This seems to be less of a problem now than a few years ago.)
The upshot is that you need to change the DNS several days before taking a
machine out of service.
Tony.
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