Why is an Active-Active configuration not recommended by F5?

Question

I was considering configuring our F5 LTMs in an Active/Active state within Cisco ACI but I read here 
that this type of configuration is not recommended without having at least one F5 in standby mode.&nbsp;
"F5 does not recommend deploying BIP-IP systems in an Active-Active configuration without a standby device in the cluster, due to potential loss of high availability."&nbsp;
Why is this? With two F5s in Active/Active mode, they should still fail over to each other if one happens to go down. Would it take longer for one device to fail over to another who is active rather than being truly standby?&nbsp;

andy_mcgrath · Answer

Simple reason is you can end up running over 50% of your F5's available resource then a failover would create lost connection.&nbsp;
F5 recommendation is to run LTM pairs as Active/Standby to prevent load every going above 100% of a single LTM. However this is only a very general recommendation and depending on your setup and traffic Active/Active is sometimes a valid approach, one I have configured a couple of times before.&nbsp;

hannes_rapp · Answer

You cannot use APM module in Active-Active. If you don't care about APM, there's nothing wrong with Active-Active if you know what you're doing.&nbsp;
The main question is, what do you expect to get out of Active-Active?&nbsp;
Personally, I see Active-Active as a great temporary solution to scale for extra capacity during annual peak-activity events. With the Active-Active setup, you can also provide the 'means of survival' until next budget year. For instance, if you run low on capacity, but the budget is already locked in for the current business year, and you cannot immediately purchase more powerful appliances. &nbsp;
In any case, it should not be the default option because of the risk of losing high-availability. AMG also mentioned that. I'll just add that constant CPU usage over 80% is already pretty bad, you want to aim for 60% or less usage. If you see 80% CPU usage in 5-minute average graphs, you can be sure there are a plenty of short bursts (that last for a few seconds) where usage is capped at 100%.&nbsp;

sumanta_88744 · Answer

Hi Sarah&nbsp;
You can successfully use active-active on LTM. If you are having TMOS version 11.x and later, then it is easier to deploy using DSC. Just ensure that you have more than one traffic group such that the 1st traffic group is active on one LTM node and the 2nd traffic group is active on the other.&nbsp;
Regards&nbsp;
Sumanta.&nbsp;

sarah_258804 · Answer

Another follow-up question to this; does anyone know of any documentation that details how to use two F5s in Active/Active mode within Cisco ACI?

Thank you all for your answers so far! It seems as though implementing Active/Active is doable in our situation I am just not sure how to go about this within ACI.