> my MX record and then in my A record add "backup.mydomain.com" to point
> to the RCN static IP?  I would set that up with a higher priority number
> so it only gets accessed when my primary MX record (which points to my
> Covad IP) is down.  Would that work?

For inbound, yes, since MX failover is built in to the MX algorithm).

The bigger problem is outbound mail. Even if you manage to get working
dead  gateway  detection so that outbound packets go out your RCN link
if  Covad  is  down  (many  cheapish  routers  can make sure this part
works),  you  have to make sure that the mailserver's public IP on the
RCN  link  has a PTR record matching its HELO -- and that PTR can't be
in  a  known  subscriber range or have be a suspicious subscriber-like
hostname (1-2-3-4-cable-consumer.rcn.net).

If  you can get the PTR-EHLO-A "roundtrip" working on your backup link
so  you  can have reliable outbound delivery in a failover state, then
you should be okay.

As  Darin  said,  this  does  not  account  for any attempt to balance
inbound  HTTP  over  the  2 links; if you can automate DNS updates (by
running  your  own DNS, or at least your own stealth primary DNS) this
can, albeit roughly, be accomplished.

And  I  don't disagree with the recommendation of just moving anything
this  sensitive  to  a  datacenter!  :)  But  there are indeed ways of
getting it done at home in a rough sense for a few $ (dual-WAN router,
Draytek  for  example).  Just  a matter of how much energy you want to
spend, and what kind of guarantees you can make to your clients.


Sanford Whiteman, Chief Technologist
Broadleaf Systems, a division of
Cypress Integrated Systems, Inc.
e-mail: sa...@cypressintegrated.com

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