active/active LTM deployment on different subnet

There are a number of reasons why you wouldn't want to do this/wouldn't work.. but I'll touch on the most obvious.

 

 

Without any intelligent DNS, aka GTM, how would you handle DNS? With the boxes being on different subnets, your VIPs are going to be different... Active/Active really wasn't designed to work like that..For something like that to work you would have to bridge the DC's.. very bad... I can keep going here but you shouldn't focus on this.

 

 

The recommended setup by F5 is Active/Standby. You will need two Boxes in each DC. There are a number of reasons why you would want this setup, redundancy, change control, etc. If you want global redundancy between DC's you are going to need additional boxes/licenses for GTMs to control this.

 

 

 

 

 

 

I might be wrong. Anyway, I think VIP will not be changed. For example, VIP C is hosted on data center A and VIP D is hosted on data center B. In normal condition, upstream router will route C subnet to data center A (physical subnet A) and D subnet to data center B (physical subnet B). However, if data center A fails, VIP C will be moved to data center B and upstream router has to be modified somehow to route C subnet to data center B.

 

 

Is this possible? Please let me know if I missed anything here.

 

 

Much appreciate!

The high level answer to your question is Yes, but the devil is in the details.

 

 

The GTM is to Datacenter Load Balancing what the LTM is to Local Load Balancing. The GTM can do Active / Active Load Balancing based on whatever criteria you provide like Geographical Location.

 

 

However, the VIP's are not "moved", the traffic is redirected at the GTM Level based on Health Checks that the GTM does on the Local Datacenter LTM's (much the same way that an LTM marks servers available or unavailable in a Pool).

 

 

I am seriously over simplifying the setup description, but it this is something you are interested in then you will need to do additional research. Keep in mind that the F5's / BigIP's do not do data concurrency for your applications (you have to do that on the back end) and that alone might kill the concept of Active / Active.

Remember in his first post he said no GTMs...

 

 

Two things will help us help you..

 

 

Can you please post a drawing of what your current setup is, stripping any private info..?

 

 

Can u also state what you're looking to accomplish? Leave out how u think it is technically going to work..a high level analysis of what u have and what u want to accomplish will do..

 

 

Thanks!

Thanks you both!

 

 

Yes, this is no GTM.

 

 

Actually, it is just an idea I think it could be possible. Anyway, I have not had a chance to test it in lab (and it may not be applicable for testing since lab has limited resource). So, I would like to know if there is anybody having done it before or having something I missed.

 

I'm pretty sure we can safely say nobody is doing that ;)

 

 

If you tell us what you're trying to accomplish from a high level we can provide you with a viable solution.

 

 

Feeling a bit good that I am the first one. :D

 

 

The situation is quite simple. Currently customer has 2 units 1 data center (I am not sure if they are active/standby or active/active). He is going to create additional data center and move half of existing system to the new data center. I assume he has network connectivity internally between the existing and the new data centers. Each data center has its own subnet.

 

 

Thanks a lot!

Hmm it may not be something to be proud of ;) j/j

 

 

If you want to be remembered in good light with your customer, provide the best solution possible. I would recommend leaving that Pair alone. Purchase a new pair for the new DC and explore your options for implementing GTMs into the picture. Ideally, another pair per DC.

 

 

This will give your customer a robust highly available environment. It will provide a mechanism for change control, upgrades, etc..

 

 

When you try to engineer around a budget, you look like a hero for the short term with your client... The minute something goes wrong all of that goes out the window and now you're a bad guy. If you're having trouble making a case for the new gear, get your local SE involved. They will be more than happy to help out with justification and pricing.

 

 

Good Luck!

 

 

 

 

well noted with many thanks!

Sure thing bud.. You can never go wrong pushing for the best solution.. If they push back, make them formally accept the risk.. If it's documented, 1 you cover your butt.. 2 they think twice about the risk and the big picture..

 

 

Definitely get you local SE involved. It's what they are there for. It wont cost you anything and when it does come time to buy they can help you there as well..