Forum Discussion
Hamish
Jan 13, 2009Cirrocumulus
Yes it can be done. I've done data centres up to 15km apart...
The things to remember are
1. For this distance, the best way would be via GTM. Except you need to have an end-2-end DNS infrastructure before it becomes practical. Some orgs don't still today.
Otherwise...
2. The front-end VLAN needs to be spanned. Because VS IP's don't change their subnets when failing over from A to B.
3. If the F5's don't have direct access to the back-end server VLAN's you need to do SNAT. Which works fine, except it is always a pain to debug, and some apps just do care about the client IP address.
4. You really want to ensure you have a non-network heartbeat link setup. I usually use either a dark fibre. e.g. a 1Gb LX SFP optical driving a reasonably shorrt fibre. But you're too far apart for that (LX will do about 10km, and the F5's don't support longer distance opticals). So you need something like a pair of switches for the heartbeat with opticals that can do 80km. e.g. 3750E's with DWDM opticals (If you have a DWDM link). Remember the heartbeat carries mirror traffic so a piece of wet string isn't good enough. It needs to have the bandwidth to carry ALL your mirrored traffic. Best bet is to have it the same speed as your front-end VLAN. Then there's no worries about it.
Apart from that, the distance is nothing.
H