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Asura2006's avatar
Asura2006
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Jul 18, 2022

Active-Standby configuration - more than 2 devices?

Hello, our company is migrating both of our data centers to new ones and we need to migrate also our F5 devices. We have VCMPs and physical LTMs, which are in HA configuration of Active-Standby pair...
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Asura2006's avatar
Asura2006
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Jul 19, 2022

Thanks for answers and Ideas.

CA_Valli 

do you have any article saying it is possible to add a 3rd device to a Active-Standby PAIR and how to configure it? 

I read this article but it is not very specific, although picture clearly shows more than 1 standby in ACTIVE-Standby configuration and it say that we can have up to 8 devices. Its for version 11.5...

https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-device-service-clustering-admin-11-5-0/6.html

or similar  for version 13.

https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-system-device-service-clustering-administration-13-0-0/4.html

 

StephanManthey 

So you are saying that i should have 2 additional devices for every cluster? So if i have 4 devices (2 vcmp hosts and 2 physical LTMs) i need to have 4 devices or even 1 VM for each VCMP guest so its even more machines. 

It looks very resource and time consuming to move devices like that...

  • CA_Valli's avatar
    CA_Valli
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    Jul 19, 2022

    Hello Asura,

    it is certainly possible to configure a three-member cluster, I just wanted to warn you again that this might be a lot of effort if you're not going to keep it however. 

    If you have multiple vCMP instances, your best setup would be setting up 1 additional VA for every vCMP cluster, and then join every VA to its respective cluster. 

    First, you need to configure VA(s) with proper licensing, IP addresses, and confirm it can ping your vADC. Hardware/software parity requirements: https://support.f5.com/csp/article/K8665

    As Stephan mentioned, make sure new IPs are permitted everywhere in firewalls, routing is on point, etc. 

    You should also be able to copy/paste load balancing configuration from bigip.conf file, something like:

    # vCMP bigip.conf configuration file was imported to VA in /shared/tmp/prod.conf 
bash
cp /config/bigip.conf /config/bigip.conf.backup
cp /shared/tmp/prod.conf /config/bigip.conf
tmsh load sys config verify
#check for errors and/or missing items
tmsh load sys config
tmsh save sys config

     

    Next, you need to trust VA in both existing vCMP. With VA's being "brand new" devices I'm not really expecting problems, but be aware that if trust breaks between existing devices you're going to have HA issues. 

    Last step will be adding the new trusted device to your device group, and then to all traffic groups. If you only have one traffic group with all floating objects, it's going to be a active/sby/sby scenario. Make sure to tune HA weights and priority on the VA so that it's the lowest.  

    You can find the full list of techdocs related to clustering here (relevant for v14): https://techdocs.f5.com/en-us/bigip-14-1-0/big-ip-device-service-clustering-administration-14-1-0.html

     

    I've checked Stephan's answer as well, this is a very well-thought and detailed procedure on how to migrate your existing cluster to new hardware with minimum effort, but I don't think it will fit your scenario since I believe your question/concern is more about ensuring service resiliency while you perform maintenance on one unit.