Using SPAN on a Cluster of cat 3550's

[j.lipsett]

If I have a SPAN session on switch 2 of a cluster of 3 3550 switches, and the span source in the local Vlan, will the span copy all Vlan trffic on all 3 switches or just for the switch I'm connected to?

[leonvd79]

Hello,

With SPAN on a 3550 you will capture only packets for a particular VLAN within the switch that has the monitor session configured for instance switch 1.

If for instance intra-switch communication takes place on either switch 2 or 3 in the cluster the frames are not forwarded accross the trunk to the adjacent switches.

To capture all data you can configure RSPAN to capture and forward frames to a monitor across a VLAN.

SPAN and RSPAN

http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225see/scg/swspan.htm

HTH

--Leon

* Please rate posts.

[j.lipsett]

Leon

Is this also the case if the switches are connected to each other with gigastack modules?

[leonvd79]

I am not shure. What I do know is, that the 3750 can be interlinked with cascase cables which creates a 32Gbps stackring.

The GigaStack GBIC provides an external connection. The 3550 is still considered a single entity, with spanning-tree and mac-address-tables in place the intra-switch traffic would leak to other stack members.

GigaStack DataSheet

http://www.cisco.com/en/US/products/hw/modules/ps872/products_data_sheet09186a00800a1789.html

--Leon

[j.lipsett]

Leon

What you say make sence. Thank you for your help. I will do a RSPAN ans see how that goes.

Regards

John