Quad-sup in VSS 6500

[Mohamed Mahmoud Abd El Khalek]

Dears,

We have a new installation of vss consists two 6500 core switches each chassis has two supervisors(VS-S720-10G-3C)

The ios release installed is     s72033-ipservices_wan-mz.122-33.SXH8

1- The standby sup in each chassis drop to rommon and i have this log :

Chassis Standby is not supported in the current release. Forcing the chassis standby in switch 1 slot 6 to drop to rommon

is that normal that vss is up and standbu sup in romon

2- i know from cisco document that if active sup fails in one chassis the the chassis will reload to make the redunadant sup be active  which i think be bad for the customer as if one server is attached to that chassis only it will be down?

Is there a release solve that issue   ?

Thanks

[Arumugam Muthaiah · Accepted solution]

Hi Mohamed,

Answer 1:

Yes, what you see is an expected behavior with 12.2(33)SXH releases.

Intrachassis Availability

The initial release of the Cisco Virtual Switching System supports only a single supervisor per chassis. If a second, or redundant, supervisor is installed in an individual chassis then the redundant supervisor will not fully boot. The redundant supervisor will stop the boot process at the ROMMON stage.

In this configuration any device connected to the chassis in a single-homed, or single-attach, manner must rely on the availability of the single supervisor. Therefore the recommendation for connecting to the VSS is to always dual-attach devices.

As a result of the single supervisor per chassis support the recovery period for replacing a failed supervisor module is undeterministic in that the recover process requires manual intervention in order to install and initialize a new supervisor in the chassis.

Beginning in the 12.2(33)SXI4 software release, Quad-Sup Uplink Forwarding is supported which allows for a redundant supervisor to fully boot Cisco IOS Software, thereby providing a deterministic recovery option for redundant supervisors in a VSS chassis.

Refer:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps9336/white_paper_c11_429338.pdf

Answer 2:

The switching modules on the failed chassis are unavailable during recovery, so the VSS operates only with the MEC links that terminate on the VSS active chassis. The bandwidth of the VSS is reduced until the failed chassis has completed its recovery and become operational again. Any devices that are connected only to the failed chassis experience an outage.

Suggestion:

Cisco recommend dual homing everything to a VSS pair of switches. you should dual home any connection to both chassis like MEC - multichassis etherchannel

Regards,

Aru

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[Mohamed Mahmoud Abd El Khalek]

Thanks for your very useful post

[Syed Siraj Uddin]

Hi,

check the below link and look for VSS Quad-Sup Uplink Forwarding

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

HTH