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New Member

Can VSS run with a single VSL link (without etherchannel)

We want to setup VSS on our 2x 6509, we have the following modules in each 6509 chassis:

1x sup720-10g-3c
1x 6724-sfp
1x 6748-ge-tx
1x X6704-10GE

Can the VSL link be configured to only use 1x of the 10gb ports on the supervisor or is there a requirement for a 10gb etherchannel to run VSS ?

(We don't have enough available 10gb ports for running a VSL etherchannel)

Everyone's tags (4)
2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Blue

Re: Can VSS run with a single VSL link (without etherchannel)

mastrboy_ wrote:

We want to setup VSS on our 2x 6509, we have the following modules in each 6509 chassis:

1x sup720-10g-3c
1x 6724-sfp
1x 6748-ge-tx
1x X6704-10GE

Can the VSL link be configured to only use 1x of the 10gb ports on the supervisor or is there a requirement for a 10gb etherchannel to run VSS ?

(We don't have enough available 10gb ports for running a VSL etherchannel)

It's only a recommendation to use both ports on the supervisor so yes you can do it with one but this is not recommended as VSS is designed to be a high availability system and you are reducing that by only have one link in the VSL. Ideally you should have a link in the VSL from another module as well.

Jon

Cisco Employee

Re: Can VSS run with a single VSL link (without etherchannel)

In case of a split-brain situation when the VSL link breaks, the active control plane transitions to standby mode and disable all the linterfaces as in operational shut down state.

The  dual active state is detected rapidly (subsecond) by any of the  following three methods:

•  Enhancement to PAgP used in MEC with connecting Cisco switches

• L3  Bidirectional Forwarding Detection (BFD) configuration on a directly  connected link (besides VSL) between virtual switch members or through  an L2 link through an access layer switch

• L2  Fast-Hello Dual-Active Detection configuration on a directly connected  link (besides VSL) between virtual switch members (supported with  12.2(33)SXI)

HTH,

-amit singh

5 REPLIES
Hall of Fame Super Blue

Re: Can VSS run with a single VSL link (without etherchannel)

mastrboy_ wrote:

We want to setup VSS on our 2x 6509, we have the following modules in each 6509 chassis:

1x sup720-10g-3c
1x 6724-sfp
1x 6748-ge-tx
1x X6704-10GE

Can the VSL link be configured to only use 1x of the 10gb ports on the supervisor or is there a requirement for a 10gb etherchannel to run VSS ?

(We don't have enough available 10gb ports for running a VSL etherchannel)

It's only a recommendation to use both ports on the supervisor so yes you can do it with one but this is not recommended as VSS is designed to be a high availability system and you are reducing that by only have one link in the VSL. Ideally you should have a link in the VSL from another module as well.

Jon

New Member

Re: Can VSS run with a single VSL link (without etherchannel)

I see, so it works but not recommended...

What happens if that VSL link goes down/or all VSL links goes down? Does it introduce a split-brain scenario, or is there any type of traffic going through non-dedicated VSL links that can tell that both switches are still up and running, preventing split-brain/ duplicate ip/macs?

Cisco Employee

Re: Can VSS run with a single VSL link (without etherchannel)

In case of a split-brain situation when the VSL link breaks, the active control plane transitions to standby mode and disable all the linterfaces as in operational shut down state.

The  dual active state is detected rapidly (subsecond) by any of the  following three methods:

•  Enhancement to PAgP used in MEC with connecting Cisco switches

• L3  Bidirectional Forwarding Detection (BFD) configuration on a directly  connected link (besides VSL) between virtual switch members or through  an L2 link through an access layer switch

• L2  Fast-Hello Dual-Active Detection configuration on a directly connected  link (besides VSL) between virtual switch members (supported with  12.2(33)SXI)

HTH,

-amit singh

Cisco Employee

Re: Can VSS run with a single VSL link (without etherchannel)

Just to add to the post, in case the previous active virtual switch members transtions to standby state, the other switch which becomes the active virtual member have the active control and data plane and keep on forwarding the traffic.

New Member

Re: Can VSS run with a single VSL link (without etherchannel)

Thanks, that clarifies my questions.

As we have 12.2(33)SXI3 we can use any of the methods you specified.

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