VLAN SPAN on Catalyst VSS?

[AJ Cruz]

Hello I can't find any clear documentation on how SPAN works in a VSS environment. I see in the documentation that you cannot configure SPAN on a VSL, but my question is regarding SPAN with a VLAN source.

I assume both chassis will capture traffic from the VLAN and send the traffic over the VSL (if necessary) to the destination port.

Is that correct?

Or does it never cross a VSL (stays local) in which case I'd have to configure two SPAN sessions and two physical destinations (one on each chassis) to capture all the traffic?

Thanks.

[pkumari4]

Hello Cruz,

SPAN Support with VSS.

The VSS supports all SPAN features for non-VSL interfaces.

The VSS supports SPAN features on VSL interfaces with the following limitations:

*VSL ports cannot be a SPAN destination.

*VSL ports cannot be an RSPAN, ERSPAN, or egress-only SPAN source.

*If a VSL port is configured as a local SPAN source, the SPAN destination interface must be on the same chassis as the source interface.

*SPAN copies are always made on the chassis where the ingress port is located.

*Two VSLs cannot share the same SPAN session.

*A pair of LTL indices are used to avoid duplicate SPAN copies across VSL interfaces. The number of SPAN sessions available to a VSS is the same as for a single chassis running in standalone mode.

With a VSL port as a SPAN source, the following limitations apply:

*The SPAN destination must be on the same chassis.

*Port-channel interfaces cannot be the SPAN destination. http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/15-0SY/configuration/guide/15_0_sy_swcg/virtual_switching_systems.html#wp1241589

You can also find the best practices for VSS at the following link: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-virtual-switching-system-1440/109547-vss-best-practices.html#span

Now coming back to your original question there are no limitations for non VSL ports. So if you are taking the SPAN on non-VSL port even though those ports under that specific VLAN are not part of the same chassis still you will be able to get capture.

Please check link here:

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/con figuration/guide/vss.html#wp1054844

General Guidelines & Restrictions for SPAN:

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/con figuration/guide/span.html#wp1079189

Regards,

Priyanka