HA

[ramziabdelhak]

Hello dear community,

i have somehow a weird question,

In a cluster enviroment " VSS, dual supervisor, dual RP ,, etc", in case the active unit goes down, does the standby unit will have access on the data plane of the ex-active unit  " can he still use its ASICs, Ports, etc " ? 

Thanks

[M02@rt37]

Hello @ramziabdelhak,

In general, the standby unit with high-availability configurations is fully capable of handling the data plane once it takes over from the active unit, ensuring continuity of network services in case of a failure. However, specific behavior and capabilities can vary based on the platform, configuration, and technology in use. Do you have a particular platform in mind ?

[ramziabdelhak]

yes, let say a VSS of 2 6500 units, what if the the active supervisore goes down, but its dataplane stays operationnal " i dont know if it is possible",  can it still be managed by the new active supervisore ? provided that SVL links are up ?

Thanks 

[M02@rt37 · Accepted solution]

OK @ramziabdelhak 

In a VSS configuration with two C6500 switches, if the active supervisor fails but the data plane (ASICs and ports) remains operational, it is generally not possible for the new active supervisor to take over control of the data plane of the failed supervisor. The data plane remains associated with the chassis, line cards, and ASICs of the original supervisor.

In VSS, the active and standby supervisors share control plane responsibilities, and the transition between them is intended for control plane failover, not data plane failover. The data plane remains distributed across the physical line cards, and the new active supervisor doesn't take direct control of the failed supervisor's data plane.

In the event of a supervisor failure, the VSS system would likely perform a switchover to the standby supervisor for control plane functions, such as handling routing and switching decisions. However, the data plane remains attached to the chassis and line cards where it was initially configured.

So, even if the SVL links are operational and the standby supervisor takes over control plane duties, the data plane associated with the failed supervisor is not automatically transferred to the new active supervisor. Data plane continuity relies on the redundancy and availability of the individual line cards and their associated ASICs.

[ramziabdelhak]

OKey i get it, verry detailed, thank you M02@rt37 ,

[MHM Cisco World · Accepted solution]

When Sup is down in unit all data plane in that unit will not work anymore.

That why you need Portchannel to both unit.

Thanks A Lot
MHM

[ramziabdelhak]

@MHM Cisco World  thank you, so we can not have a Control plane failure only ,?

[MHM Cisco World]

Quad Supervisor VSS Deployment on Catalyst 4500 Switches Configuration Example - Cisco

the Quad Sup is solution here.

Thanks A Lot
MHM

[ramziabdelhak]

Intressting, it seems like a large ISP grade solution, dont you think so ?

I thank you for this generosity

[MHM Cisco World]

Yes for ISP and DC.

You are so welcome.
have a nice day

[Joseph W. Doherty]

Consider if a line card, stack member, etc. fails, do you expect any of its ports to continue to work?  If so, why?  If not, ports on a "brain" card should work?  If so, why?