From: marty [mailto:[EMAIL PROTECTED]]
>> Ok, so now you have redundant routes to your network. The
>network can exist
>> in multiple physical locations connected by a VLAN link to
>make it appear
>> all on the one subnet. Each of your ISP routes would go to
>the different
>> physical location.
>
>that was my stumbling point... my understanding was that you could
>multihome a service (ie. a cluster of MX servers) or a
>physical box, using
>**different IPs**... but having a single IP would need to be the same
>connection to a network -> creating a SPF... so is it possible to
>multihome using the same IP or does the VLAN allow you to "trick" the
>network (and if so, how ?!?) ??
The VLAN is only there to separate physical locations.
You have many boxes in a cluster all responding on the same IP. The point
of clustering is to make many machines appear as one. I honestly don't know
the exact mechanics of how this is done at a TCP level but I do know it is
possible. It actually doesn't matter if the second site is merely acting as
a hot standby (active/passive) or is doing work (active/active).
>> Now you have one network in two physical locations with a
>separate route to
>> each location. You then create a cluster of machines to
>respond on a single
>> IP address. You connect these through a separate cluster
>interface and
>> situate half the cluster at each location. The interconnect will be
>> interesting, but it is possible.
>
>i thought it would have been much easier to have multiple MX
>records with
>identical priority so that mail servers will use them randomly or on a
>round-robin...
Quite probably. Many web sites have gone from round-robin DNS to a single
IP though. Not sure about the logisitics behind it - just know it is
possible.
John Wiltshire
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