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spanning packets and VPLS

Hi,

I am bit confused whether spanning tree packets uses the native vlan (ie 1) or goes as untagged ? If it is untagged, how can associated the spanning tree to the VPLS considering that I am using lots of sub-interfaces considering I am using MSTP.  I need the spanning tree to flip over the BGP based multihome VPLS.

regards,

Skanda

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Cisco Employee

spanning packets and VPLS

Hi Skanda,

BPDU handling in VPLS environment is not that straighforwared as customer STP is transparent to the SP. Customer BPDUs are dropped or forwarded transparently depending on the configuration.

In general the default behavior is:

  • UNI is dot1q tunnel port

By default, customer BPDU will be dropped. With L2PT configuration, STP BPDU, CDP and VTP packets can be  tunneled through

  • UNI is dot1q trunk port

By default, customer STP will interact with SP STP. In order to tunnel customer STP BPDU, STP must be disabled for that customer VLAN on SP switch. Recommend to config “spanning-tree bpdufilter enable” on SP switch.

MST behaviour slightly differs from STP and RSTP; BPDUs for MST are carried untagged on the native VLAN. If you want to transport MST BPDUs over VPLS, you will need to QinQ all of the MST VLANs + the native VLAN through your VPLS SVI xconnect.

Riccardo

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