[BUGS] mail servers and ip aliasing

[jonathan michaels]

On Tue, May 13, 2008 at 04:17:35PM +1000, Jerahmy Pocott wrote:
> 
> On 13/05/2008, at 12:38 PM, jonathan michaels wrote:
> 
> > reading about stuff like ip-aliasing gets a bit confusing at
> > time, so many articles so many different way of doing it ..
> > grr. the only problem is that i need this box to keep its
> > current 'identity' as its doing some small but important stuff.
> 
> > are there any things that i should be mindfull of it i alias
> > this box with the current mx hosts ip address to this server
> > then setup a new sendmail/postfix/exim network mail server on
> > teh new box.
> 
> So you want this machine to have multiple IP addresses on the one  
> interface?

and within the same subnet .. i'm not so bold as to go across
that boundary .. well not today at any rate <gentle grin>.
 
> It will take over an IP that is currently being used as the MX?

yes, that is correct.

> This should work fine, but you want to be careful of what services  
> listen on which address, since most by default listen on all  
> interfaces..

smtp thats all thats involved in this project.

> Your router/switch needs to associate that interfaces MAC with both  
> addresses,

is this as simple as getting the relevent host(s) rebuilding
the arp table ? or ???

this is only thing that sort of concerns me, also, is if pf
will get its knickers in a knot (so to speak). dosent seem to
be raised in teh literature (not in yahoo at anyrate if i
remember correctly).

> but that should happen automatically unless you have a  
> complicated topology going there.. I'v had trouble with putting one  
> interface on different subnets before...

i'm thinking off adding a rdr (redirect) clause to point all
incoming smtp traffic at the mailserver ip address, don't know
if this is affected by mac-address issues --- dosent seem to be
raised in teh literature (not in yahoo at anyrate if i remember
correctly).

to reiterate all of this is inside of one subnet, (i've
subneted my /24 into /28's, i think, 16 address chunks but i
only use the one subnet. so its not what can be called
'complicated' ...grin.

much kind regards

jonathan

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