F5 Questions

1.How active/active F5 loadbalancer work?

both (or more in a DSC) big-ips will handle the traffic. this is done based on traffic groups. it is not true active / active where traffic for one virtual server can be handled on multiple big-ips. it is more that multiple big-ips can handle traffic, but traffic for one virtual server will always be handled on one big-ip at a time.

also see: http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip_tmos_implementations_11_0_0/3.html

2.What is Virtual / Server clustering?

not sure, never heard about this term. with version 11 you do have a device server cluster which is the group of big-ips working together.

also see: http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-device-service-clustering-11-2-1/1.html

3.Why F5 recommend to re-activate the F5 license before upgrade?

they don't just recommend, it must be done. this is because you need an active license to be allowed to upgrade. if you don't do it and after the reboot the big-ip notices it it won't start correctly.

see also: http://support.f5.com/kb/en-us/solutions/public/7000/700/sol7727.html

4.Why cant we upgrade the F5 from Version 9 to 11?

because there are too many chances in the way things work. this is quite normal in IT, small steps are usually possible bigger changes will need to be done in smaller steps.

if you plan this upgrade it might be wise to involve your F5 partner, if this is the first time you probably will run into many issues a partner already knows about and can help with. if you won't then at least try to find a way to test the upgrade before doing it in production.