ISP inbound failover without BGP

[Eric A Louie <elouie () yahoo com>]

This may sound like dumb question, but... I'm used to asking those.

Here's the scenario

Another ISP, say AT&T, is the primary ISP for a customer.

Customer has publicly accessible servers in their office, using the AT&T address space.

I am the customer's secondary ISP.

Now, if AT&T link fails, I can provide the customer outbound Internet access fairly easily.  So they can surf and get 
to the Internet.

What about the publicly accessible servers that have AT&T addresses, though?

One thought I had was having them use Dynamic DNS service.  

Are there any other solutions, short of using BGP multihoming and having them try to get their own ASN and IPv4 /24 
block?


It looks like a few router manufacturers have devices that might work, but it looks like a short DNS TTL (or Dynamic 
DNS) needs to be set so when the primary ISP fails, the secondary ISP address is advertised.