Catalyst 6500 VSS and access switches

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Jul 25th, 2008
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Need to deploy a VSS solution:

actually the topology on the core is configured with 2 switch cisco core A,B with 2 etherchannel for back to back connection and with 16 EtherChannel vs the access switches configured with mode on and PAgp (8 etherchannel on core switch A vs the access switches and 8 etherchannel on core switch B vs the access switches).

On the cisco docs about the VSS I found the feature "Multichassis EtherChannels" (LACP 1:1 Redundancy / Enhanced PAgP / BFD) but as I can't utilize this feature on access switches vs the new core VSS how proceed (the feature needs to be enabled at both ends of the link? ) ?

FOR Enhanced PAgP:


For dual-active detection to operate successfully, one or more of the connected switches needs to be able

to process the new TLV. Catalyst 6500 series switches with Supervisor Engine 32 and Supervisor Engine

720 have this capability, if they are running Cisco IOS software release 12.2(33)SXH1 or later. For a list

of other Cisco products that support enhanced PAgP, refer to Release Notes for Cisco IOS Release

12.2(33)SXH and Later Releases.


Can I configure the standard etherchannel on the VSS vs the access siwtches ?

Witht this 'standard' configuration I lost only the 'Dual-Active Detection' feature on the access switches ?

Best regards.

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Overall Rating: 4 (1 ratings)
ROBERTO TACCON Fri, 07/25/2008 - 06:56
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Thanks for the reply.

As you indicate I can configure the 'standard' etherchannel if also the etherchannel is configured on both the 2 VSS switches vs the SAME access switch:

VSS switch A port g1/1 vs access switch C port g0/1

VSS switch B port g3/3 vs access switch C port g0/2

As the VSS switch A and B are a single virtual switch the spanning tree block or not the etherchannel port g0/2 on the access switch ?


a.alekseev Fri, 07/25/2008 - 07:02
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VSS switch A and B are a single virtual switch.

Think about VSS like a stack with 3750.

If you have etherchannet between VSS and switch C no ports will be blocked.


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