Depends on the application,
SIP, VPN, SMTP, etc just setup both IPs and let the end-user application figure it out (SIP-UA register to both IPs for example) HTTP/HTTPS setup a proxy server in a colo that is multi-homed to frontend the requests. Then it can load balance traffic over both IPs. DNS TTL ‘tricks’ are just that, they work ‘kinda’ Fatpipe? Crazy expensive IMHO but I hear they work ok. -Matt -- Matthew S. Crocker President Crocker Communications, Inc. PO BOX 710 Greenfield, MA 01302-0710 E: matt...@crocker.com P: (413) 746-2760 F: (413) 746-3704 W: http://www.crocker.com On Mar 3, 2014, at 8:11 PM, Eric A Louie <elo...@yahoo.com> wrote: > 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. >
