browser-handled site failover

@Hamish - It works fine.

 

 

@Robert - You need to only hand out one response to A/AAAA requests on TM; then you are fully leveraging the synergy between LTM and GTM to service new records with the best available A or AAAA response, and using the HTTP falback feature in LTM to redirect when the pool member is down. The only time you have to wait for a timeout is if you lose the LTM HA pair or the whole data center goes dark - both bigger problems than slow redirects. LTM will tell GTM when service is restored and then GTM will re-insert the LTM virtual server into rotation.

 

 

If you have non-HTTP traffic, then you probably don't have a way to redirect the traffic in the application layer protocol, so the best thing to do is send an RST (which the LTM should do if the pool members are unavailable according to the setting of Action on Service Down in the pool config). The more complex alternative is to set the virtual server address of the remote datacenter as a pool member, use priority group activation, and set the remote data center as the fall back priority group; this will send the traffic from dc1 to dc2 (and back again) if the servers in dc1 go down. It will also send new connections to the restored priority group when the pool members come back on line.

 

 

The whole point of only issuing one A/AAAA response at the GTM is to keep this problem from happening. Older versions of Windows/IE were broken and would timeout cached DNS records in minutes, even if the TCP SYN never elicited an ACK; that is mostly fixed now, so you should be OK in setting responses to 1 and perhaps lowering your persistence timeout on GTM.