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MVP
Posts: 1,111
Registered: ‎10-11-2011

Tweaking RAP LMS Failover

Having some issues with RAPs failing over to backup LMS due to missed heartbeats.  It's a RAP here and a RAP there, not all at the same time that they fail over, so I suspect it's random packet loss at the branch offices.  I see two options that will configure LMS failover:

 

Tunnel Hearbeat Interval = 1 sec

Bootstrap threshold = 8

 

Is there a science to configuring these values or just trial and error to find what works best?  Quick failover is not a requirement as I really only want the RAPs to failover if there's a serious outage.  That being said I wouldn't think it matters much how I set these values, but I'm still curious to know how others would approach this.

 

Thanks.

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Aruba
Posts: 1,290
Registered: ‎08-29-2007

Re: Tweaking RAP LMS Failover

I would consider raising the bootstrap threshold to 12 to start with.


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ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite
Posts: 21,269
Registered: ‎03-29-2007

Re: Tweaking RAP LMS Failover

A RAPs bootstrap threshold is 30 minimum, even if in the configuration it says 8.  You should configure it at 40 or above:

https://arubanetworkskb.secure.force.com/pkb/articles/FAQ/What-is-the-default-bootstrap-threshold-for-Remote-and-Campus-APs-on-an-Aruba-Controller

 

 



Colin Joseph
Aruba Customer Engineering

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MVP
Posts: 1,111
Registered: ‎10-11-2011

Re: Tweaking RAP LMS Failover

Ahh, interesting little caveat. Would've never known that was the case. Thanks for pointing that out. I'll bump it to 40 and see what happens.

Also, will the RAP prioritize heartbeat traffic over user traffic is there's contention on enet0? Some locations have every small pipes to the internet so I think it's possible that heartbeat traffic is getting dropped at the source.
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Aruba
Posts: 1,290
Registered: ‎08-29-2007

Re: Tweaking RAP LMS Failover

If there is QoS enabled on those wan links, you could try changing the heartbeat DSCP.  From the CLI guide,

 

Define the DSCP value of AP heartbeats.
Use this feature to prioritize AP heartbeats
and prevent the AP from losing connectivity
with the controller over high-latency or
low-bandwidth WAN connections.


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ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite
Posts: 21,269
Registered: ‎03-29-2007

Re: Tweaking RAP LMS Failover

Michael_Clarke,

 

Have you ever used that feature?  It will tag the the outer heartbeat packets with whatever dscp you want, but the entire infrastructure from the RAP to the controller must support prioritizing those packets, otherwise it will not work as intended.



Colin Joseph
Aruba Customer Engineering

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Aruba
Posts: 1,290
Registered: ‎08-29-2007

Re: Tweaking RAP LMS Failover

I've never used that feature.  Just thought it might be what thecompnerd is looking for, but as you say, if it's not setup end to end, it won't work as intended.


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ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
MVP
Posts: 1,111
Registered: ‎10-11-2011

Re: Tweaking RAP LMS Failover

Unfortunately, the remote locations are not setup for QoS. I was hoping by
default that the RAP would protect heartbeat traffic via high priority
queue.
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Super Contributor II
Posts: 429
Registered: ‎01-19-2011

Re: Tweaking RAP LMS Failover

The RAP WILL protect the traffic as it sends it but its up to the next device in the chain to do the same. Its like the RAP saying to the the next hop "make this a priority - its really important" and the next saying "yeah, whatever, not interested" and sending it with no specific priority. QoS has to be end-to-end with all devices in the chain between source and destination honoring the markings, or translating them to an equivalent priority in a different system.

MVP
Posts: 1,111
Registered: ‎10-11-2011

Re: Tweaking RAP LMS Failover

Thanks for the input all.  I'm still having a lot of issues with this.

 

Also, I'm wanting to understand what the max request retries is for.  Based on what the user guide, this is my understanding: Once the bootstrap threshold is met, the AP turns off the radios and attempts to connect to the primary LMS.  If the primary LMS is not reachable (based on max request retries count) the AP will attempt to connect to the backup LMS or reboot.  Is that right?

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