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One-sided LACP (to keep STP working...)

costaspal
Beginner
Beginner

Hello people !

I face a situation where, STP needs to keep doing its job - i.e. block one of the links, hence deliberately not setting the two uplinks in EtherChannel - but, on other side we have two (Core) Nexus switches in vPC so the dual connections from the 'remote' switch are treated as 'standalone' unless set-up as EtherChannel..!

Since it's a production environment, I'm curious whether this scenario would work before I actually connect the second link.

 

The reason for this is that in between the two links, there are L2 'passive' / passthrough devices that do not have any other failover mechanism so I need to rely on STP, to have one link blocked until the 'other' device fails and stop passing traffic.

(See attached draft).

 

I'm trying to 'fool the system'; I know...

The thing is that I'm trying to keep some level of redundancy and want to avoid landing both remote link to the same physical switch - if possible.   Otherwise the scenario works; I tried it with single switches alongside.

 

Any thoughts ?
Thanx guys !

 
 

 

1 ACCEPTED SOLUTION

Accepted Solutions

costaspal
Beginner
Beginner

Thank you all for giving this, a try...!

As it turned-out, the 'misbehavior' was with the L2 devices in-between.    They were dropping packets <64Bytes - presumed not compliant to IEEE standard - hence, dropping STP related traffic.

I talked to the vendor and they had a new firmware just released for that purpose.

So, case dismissed.

Thanx again

Costas

View solution in original post

5 REPLIES 5

Thanx for jumping right in !

This actually is very close to what I 'need' to do and to my understanding, it could actually work...

Surely taken into consideration !

If this finally points to a valid solution I will mark your answer accordingly...

Nop !!

 

"One-sided" LACP on vPC enabled Nexus switches, did not work on our case - neither in "active" nor "on" modes.

MHM Cisco World
Advisor
Advisor

OK, Now the C9000 will connect to vPC NSK peers via two link, 
if you allow vPC or non -vPC VLAN and you don't config PO in NSK Peers the NSK peers and C9000 will be work as any three SW connect together (the vPC or  Non-vPC VLAN need to allow in Peer-link).

the C9000 will see one two BPDU, 
one from Primary and other from Secondary vPC Peer 
this BPDU will contain the vPC mac address of root ( there are only one root in STP domain) 
the C9000 will elect root port and BLK the other port.

here if the Link is down or NSK peer is failed the C9000 will FWD the previous BLK port. 

I think this is what you looking for and this what doc. I share is explain.

for your case I don't know why you need to run PO between C9000 and both NSK peer if the C9000 not run PO.

costaspal
Beginner
Beginner

Thank you all for giving this, a try...!

As it turned-out, the 'misbehavior' was with the L2 devices in-between.    They were dropping packets <64Bytes - presumed not compliant to IEEE standard - hence, dropping STP related traffic.

I talked to the vendor and they had a new firmware just released for that purpose.

So, case dismissed.

Thanx again

Costas

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