Wired Intelligent Edge (Campus Switching and Routing)

Occasional Contributor I


Hi all,


We're testing out Aruba switches (specifically the 2500 series).  We've stacked together two switches and have them uplinked to our Cisco Nexus core.  One uplink originates from one stack member, the other uplink is on the second stack member.  The uplinks are bound in a port channel (lag) group.. 


We did some failover testing and failures on the stack cables and uplinks caused no network disruption.  However, when we physically failed either member of the stack (primary or secondary), the traffic on the switch that remained up experienced a significant (ie >40 seconds) disruption.  In our current Cisco environment, and with HP switches we're testing, this is not the case. 


Anyone know how to mitigate this?

Re: Stacking

Not a clue right now.


But if you purshased the switches with their respective support, go and open a support case.  They will asnwer you faster than people will do here.

If madjali is around well he might be able to asnwer you.


Could be a bug though... did you check the release notes and upgrade the firmware of those switches?




Product Manager - Aruba Networks
Alternetworks Corp
Frequent Contributor II

Re: Stacking

You running lacp between two nexus in a vpc configuration? 7k or 5k?
Occasional Contributor I

Re: Stacking

Correct. Vpc with Nexus 7k. Uplink failure from the stack to Nexus works great. It's failure of a stack member. I would think it's some kind of issue with Aruba stacking?

Re: Stacking


While there is currently support for configuration syncronization between all members of the Arubastack, we do not currently support protocol syncronization. As such when the primary fails, the secondary has to re-learn things like Spanning Tree, OSPF routes, etc which will lead to a temporary impact on forwarding. If this is a L2 configuration, you can currently mitigate this by disabling Spanning Tree and enabling loop-protect to minimize the impact of STP re-sync. With respect to the port-channel, are you using a static LAG or a dynamic LAG using LACP? If dynamic, are your timers set for short or long (default)?


In the secondary member failure test case, are you actually seeing the primary actually continue forwarding? Reason I ask is whether you have split-detection enabled or disabled. If enabled (default), then in that situation specifically with two member stacks, the primary believes that it has failed for some reason and actually transitions to a dormant state. To avoid that, you need to disable split-detection.


In terms of the lack of protocol syncronization (aka Non Stop Forwarding/Bridging/Forwarding), I highly recommened you submit a feature request through the idea portal.


Best regards,




*** Edited - Should have said loop-protect, not loopguard ***

Frequent Contributor II

Re: Stacking

Sure,  just showing total selfish interest.  :smileywink:


Can you show the CAM table on one of these aruba switches? 


If so can you post the switching table during normal operation, and then again during one of the stack member failures?


I guess maybe the switching table on the aruba may have stale information in it's table, and has not flushed it out when it's partner dies. 


Also have you verified the nexus is forwarding frames across the vpc peer link to get to the last surving member of the stack?  


Can you show LACP neighbor on the aruba too?  It must be getting confused and the stack member time out must being aged out?  Waht do you reckon?  Maybe compare that with the cisco - which, I have to say - is going to be good  right?


It's be great to see this - if you have time.  thanks a million.  I appreciate you are helping me so any thanks in advance.

Frequent Contributor II

Re: Stacking

hi Madani


when you say protocol sync - do you mean like LACP is unsupported (I know with cisco 3750s you used to only do cross stack etherchannel without procotol negotiaion - may have changed)


same kind of thing?  Can you confirm?

Frequent Contributor II

Re: Stacking

on the cisco does the lacp neighbor show up as the same partner ID - or does it form like a secondary aggregator?  the LAG id (just as already been mentioned needs to match - that is the cisco needs to see the same LAG id to form the port channel)


the LAG id needs to match from both aruba stack members - otherwise it will confuse the hell out of the cisco!!!


Maybe your LACP is failing and you are getting a spantree topology change?  (as already said I think LOL)



below I have issued a VPC check for port channel 1001, from my 7k called "whatever" ( hostname names changed to protect me) - sorry if I am tellign you how to suck eggs  :)




whatever# sh vpc consistency-parameters vpc 1001

        Type 1 : vPC will be suspended in case of mismatch

Name                        Type  Local Value            Peer Value
-------------               ----  ---------------------- -----------------------
STP Port Type               1     Default                Default
STP Port Guard              1     Default                Default
STP MST Simulate PVST       1     Default                Default
lag-id                      1     [(7f9b,                [(7f9b,
                                  0-23-4-ee-be-65, 83e9, 0-23-4-ee-be-65, 83e9,
                                   0, 0), (7f9b,          0, 0), (7f9b,
                                  0-23-4-ee-be-6f, 8fa1, 0-23-4-ee-be-6f, 8fa1,
                                   0, 0)]                 0, 0)]
mode                        1     active                 active
Speed                       1     10 Gb/s                10 Gb/s
Duplex                      1     full                   full
Port Mode                   1     trunk                  trunk
Native Vlan                 1     257                    257
MTU                         1     1500                   1500
vPC card type               1     Clipper                Clipper
Allowed VLANs               -     1,101-103,107,602      1,101-103,107,602
Local suspended VLANs       -     -                      -

Guru Elite

Re: Stacking

Protocol sync is referring to layer 3 routing protocols and STP/RSTP. 


LACP is supported and is recommended.

| Tim Cappalli | Aruba Security | @timcappalli | timcappalli.me |

NOTE: Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba or Hewlett Packard Enterprise.
Frequent Contributor II

Re: Stacking

Great stuff. Just sounded like a lacp adjacency problem, causing spanning tree to take control of failing over. But obviously I don't have the information. Many thanks for the confirmation.
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