Score bonus & failover condition

We use a trunk with 2 interfaces and this is what we ended up doing. We don't need the 2nd 10 gig interface active so we only have 1 interface up per trunk and this is working ok.

 

The weight we assigned was 60 and we have 2 interfaces so each interface has to be up to get a weight of 60, with 1 interfaces down the weight is 30 and on the active unit you add the active bonus making the total 55 on the primary as shown here and the highest score becomes active.

 

LTM1:Eval:Active:In Sync] config tmsh show sys ha-group HA1 Sys::HA Group: HA1

State enabled Active Bonus 25 Score 55

 

On the standby it looks like this

 

(LTM2)(cfg-sync In Sync)(Eval:Standby)(/Common)(tmos) show sys ha-group all Sys::HA Group: HA1

State enabled Active Bonus 25 Score 30

 

Consider when you activate the 2nd interface in the trunk. Now the full weight of 60 is added to the active bonus of 25 so that would be a score of 85 and the standby would be 60. If you lose 1 of the 2 trunk interfaces on the active the score changes to 25 + 30 or 55 which is lower than the standbys 60 so a single interface failure out of 2 in this configuration would trigger a failover. Consider how you want this to work fail over from 1 interface or both? So when we do activate the 2nd 10g interface we could increase the bonus to 35 so the one interface weight of 30 + active bonus 35 (65) would still be higher than the standby which is at 60.

 

Hi,

 

Thanks for your answer. This is indeed a way to avoid this situation.

 

But here I'm trying to understand why we have this behavior (failover or not in case of equality of the score). It looks like it is link to the management IP for the decision...

 

I'm curious to know how the management IP is used as a "tie breaker"? is there a SOL that details this?

 

i understand when ha-group score is equal, ha score (not ha-group score) is used to break tie.

 

Manual Chapter: Managing Failover

 

http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-device-service-clustering-admin-11-5-0/8.html

 

Dylan, it is in the link posted by nitass, here is the extract.

 

About matching device utilization values In rare cases, the BIG-IP system might calculate that two or more devices in a device group have the same lowest device utilization score. In this case, the BIG-IP system needs an additional method for choosing the next-active device for an active traffic group.

 

The way that the BIG-IP system chooses the next-active device when device utilization scores match is by determining the management IP address of each matching device and then calculating a score based on the highest management IP address of those devices.

 

For example, if Bigip_A has an IP address of 192.168.20.11 and Bigip_B has an IP address of 192.168.20.12, and their utilization scores match, the BIG-IP system calculates a score based on the address 192.168.20.12.