On Mon, Mar 3, 2014 at 8:11 PM, Eric A Louie <elouie@yahoo.com> wrote:
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?
Hi Eric, I went through this a couple years ago with continuity of operations planning. The bottom line is: with the notable exception of low-activity electronic mail, switching the address record in the DNS entry will generally not work as expected. For folks serious about reliable access to their servers, BGP isn't just the best way, it's the only way. Reasons why dynamic DNS fails to perform as expected include: * Web browser DNS pinning can result in a customer's web browser holding the old IP address indefinitely. * Host-level caching of looked up names which discards the TTL. Remember: your desktop or laptop performs lookups against multiple name services, e.g. DNS, /etc/hosts, lmhosts, NIS+. DNS TTL is no longer in scope once the name to address map enters the generic host lookup mechanism. Most OSes have a fixed timeout of one sort or another, some old ones as long as 24 hours. * Custom applications with either IP addresses hardcoded into the configuration or with getaddrinfo() called only once and the resulting IP address held for the lifetime of the application. * Anti-spam systems block IP addresses when receiving large quantities of email from formerly-quiescent IP addresses. This is a problem if your mail server sends a lot of email and suddenly switches to a new sending IP address. Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004