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Community Member

Tracking GLBP Priority

Hi,

I'm trying to track GLBP priority much like we do with HSRP.  I understand GLPB's tracking of the AVFs but that's not what I want to do.  I want to be able to not only decide what my AVF's are but also I want to track the AVG's.  I'm not able to find a way to track just the AVGs other than to manually go into each interface and change the priority.

Here's my rational/scenario:

I have two upstread L2/L3 6509's that terminal all of my VLANs.  On thos VLANs I have GLBP configured with my primary 6509 as the AVG (Priority 150) and the secondary 6509 as the Standby VG (Priority 100).  My AVFs vary depending on tracked interfaces and that portion works fine for me.

When I want to perform maintenance on the primary router, I'd like to shift traffic away from that router completely.  So I can do that with a tracked interface which would cause my weight to drop below the lower weight limit and the Standby VG now becomes my AVF for the two virtual MACs.  The AVG is still my primary 6509 and I want to also shift that but I can't find a way to do that.  i.e. I want what is the standby VG to take responsibility for responding to the ARP requests for the gateway address.  As it is now, the primary is not an AVF but it is responsible for handling the ARP requests.

Is there a way to accomplish what I need?

Thanks.

Casey

3 REPLIES
Cisco Employee

Re: Tracking GLBP Priority

Hello Casey,

Personally I am not aware of any possibility to modify the priority (as opposed to the weight) of a GLBP router via tracking to force it to relinquish the AVG role once an interface or a tracked object is down. I personally believe that the lack of this functionality is perfectly logical - I am no doubt going to state the obvious but I believe it is important for this issue. The role of an AVG is to assign vMAC addresses and respond to ARP requests, and this does not require that the AVG has any live connection to an outside network. In other words, the role of AVG is purely about managing the GLBP group without actually forwarding data to other networks. Therefore, there is no general need to track an interface or other object and derive the AVG priority from it.

I am afraid that the only possibility for now is indeed to temporarily manually lower the priority (and the weight) of the router under maintenance to prevent it from becoming AVG and AVF.

Best regards,

Peter

Community Member

Re: Tracking GLBP Priority

Thanks Peter...I was afraid of that.  I couldn't find any clues on how that could be done other than to go into each interface (I have many of those).  It seems Cisco overlooked that operational feature.  I have tested failover and it is pretty quick but I'm of the school of thought that if I want to place a device in maintenance mode then I should see zero production trafffic through it and no dependency on it for any production functions.  So in my case I wanted to shift the AVG responsibility to the SVG so I can gracefully take it out of service.

Casey

Cisco Employee

Re: Tracking GLBP Priority

Hello Casey,

I see your point and I agree. What I am thinking about is using some kind of automation if available - EEM scripts, TCL scripts or perhaps even SNMP to automate this task. These scripts would in essence do the same you are doing manually now - go over every interface you need and lower the GLBP priority and weight but you would simply call that script once. Do you believe there would be a way to use some of these?

Best regards,

Peter

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