Forum Discussion

Martin_Vlasko's avatar
Martin_Vlasko
Icon for Altocumulus rankAltocumulus
Dec 18, 2017

Load balance to node in the same DC where VIP is active

Hi,   We have following (simplified) scenario:   Two data centers: DC1, DC2.   Two F5 LTMs, one LTM in each DC, they run in active/standby mode and have one VIP configured.   Two applicat...
application delivery
irule
iRules
location awarness
LTM
Farshad_249798's avatar
Farshad_249798
Icon for Cirrus rankCirrus

You need to track a unique local id somehow and then use irule to select pool member based on that id. Haven’t tested this but I would use tcl_platform(machine) to get hostname assuming they are different.

 

Simon_Blakely's avatar
Simon_Blakely
Icon for Employee rankEmployee
Dec 18, 2017

That isn't really an HA configuration, it is a DC failover design.

 

LTM HA requires that each LTM in the HA pair has the same view of the network, and treats all the pool member as equivalent. You want one pool member to be associated to one LTM in one DC, and the other pool member to be associated to the other LTM in the other DC. LTM HA cannot be configured to do this.

 

You also have the issue of moving an IP address (the virtual IP) from one DC to another - how are you planning to make that work if the DC's have different uplinks to the internet?

 

For a DC failover design, you would have a LTM (or LTM HA pair) and virtual in each DC, and use a F5 GTM/DNS to send traffic to whichever DC is preferred. If the GTM detects that a DC is down (pool member,virtual or upstream link failure), then it starts sending traffic using the wideIP to the other DC until service is restored.