Quad-Sup VSS Deployment

[Iker Santamaria Molla]

Hi all,

We are preparing the migration to VSS in Quad-Sup scenario (two supervisor per chasis) and, after reading lots of documentation on the subject;

i have the following question:

If the ACTIVE Supervisor fails,the HOT STANDBY Supervisor assummes the ACTIVE rol (Inter-chasis redundancy) but, i am not sure if solution' s behaviour is that the chasis where supervisor failed,will reboot as in the Dual-Sup deployment?

Or, it will make a switchover to its local Standby Supervisor (Intra-chasis) and maintain its linecards active?

Thank you very much.

Regards!

[JOHNY JOSEPH]

In a VSS scenario , initial software releases (Minimum OS --Cisco IOS® Software Release 12.2(33)SXH1) supports only a single supervisor engine per switch member (or chassis)..This restriction was planned to be removed in a future software release. But not sure whether we can have dual sup in a chassis. You may check on the same once,

Regards,

Johny

[Iker Santamaria Molla]

Hi Jonhy,

first, thanks for your answer and interest but according to Cisco the restriction, i think that was removed in 12.2(33)SXI4.I have 12.2(33)SXI5.

Reading Cisco documentation, I understand that the methods of redundancy are as follows:

• SSO/NSF for the entity VSS (Inter-Chassis redundancy)
• RPR-Warm for local redundancy in each 6500 chasis (Intra-Chassis redundancy)

My question is, with RPR-Warm redundancy, when the ACTIVE supervisor fails,switchover occurs only in the supervisor or otherwsie, in the entire chassis.

Some diagrams attached.

Thanks and sorry for my English!

Regards.

Iker

[Giuseppe Larosa]

Hello Iker,

see C6500 12.2SX configuration guide fig. 4-5

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vss.html#wp1020417

>>During the bootup, once the chassis level role is  resolved, the ICS downloads the image from the in-chassis active (ICA)  supervisor engine. Once the supervisor engine is booted with the image,  it will function in the same way as a DFC line card. All applications  running in virtual switch (VS) view the in-chassis standby as a DFC line  card. 

my understanding is the following:

So when the VSS active supervisor fails the VSS standby in the other chassis takes over, the other supervisor that is in the same chassis of the previously active supervisor is then promoted to VSS Standby role from acting as a DFC ( SP running, RP stucked in rommon).

only the VSS standby is in SSO with the previously active supervisor, the  ICS has not the state in sync with it as they speak RPR that is a looser form of redundancy.

It is the fact the ICS is seen as a DFC that has allowed to add support for Quad supervisors, but the ICS is not ready to take over when the in chassis active supervisor fails.

Another point of view : quad supervisors is made by putting in SSO two pairs of supervisors that are in RPR instead of having simply two supervisors.

both SSO and RPR work on two objects not four at the same time.

Hope to help

Giuseppe

[Iker Santamaria Molla]

Hi Giuseppe,

thanks for your quick response, it´s very clear.

I  thought the same than you, but I still had a doubt: the entire chassis reload when the switchover occurs? 

Thank you very much.

Regards.

Iker

[Giuseppe Larosa · Accepted solution]

Hello Iker,

I have no direct experience with a quad supervisors VSS

documentation  at the same page says:

>> VSS stateful switchover—When the in-chassis active  supervisor engine crashes, a switchover occurs and the whole chassis  reloads (including the ICS) during which the standby supervisor engine  takes over as the in-chassis active supervisor engine.

so yes the entire chassis x is reloaded ( not the whole VSS)

Hope to help

Giuseppe

[Iker Santamaria Molla]

Hello Giusepe,

you have been a great help to me.

I´ll tell you how it goes migration!

Iker.

[Rahul Kachalia · Accepted solution]

Hello Iker,

In current IOS version the virtual-switch chassis and all installed modules in that chassis will reset when ICA (SSO ACTIVE/HOT_STANDBY) supervisor is reset.

Refer to Chapter 2 and 4 for more detail on Quad-Sup migration, deployment and expected recovery mechanic from following guide:

Borderless Campus 1.0 Design Guide

thanks,

rahul.

[Iker Santamaria Molla]

Thanks Rahul!