This may sound like dumb question, but... I'm used to asking those.=0A=0AHe= re's the scenario=0A=0AAnother ISP, say AT&T, is the primary ISP for a cust= omer.=0A=0ACustomer has publicly accessible servers in their office, using = the AT&T address space.=0A=0AI am the customer's secondary ISP.=0A=0ANow, i= f AT&T link fails, I can provide the customer outbound Internet access fair= ly easily.=A0 So they can surf and get to the Internet.=0A=0AWhat about the= publicly accessible servers that have AT&T addresses, though?=0A=0AOne tho= ught I had was having them use Dynamic DNS service.=A0 =0A=0AAre there any = other solutions, short of using BGP multihoming and having them try to get = their own ASN and IPv4 /24 block?=0A=0A=0AIt looks like a few router manufa= cturers 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.
The usual solution is to get the public servers stuck in a colo that's multihomed. Most of the other solutions tend to be a bit dodgy. If your gear is sufficiently competent, you can hack up a solution with multiple addresses for each of the servers (one on each ISP) and then use a short TTL to fail over, but this has more of "fail" than "fail over" about it, because there are a bunch of issues that typically result. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.