Interoperability RPVST and RSTP

[bradcl]

Hi all,

I just wanted to get some advice about interoperability between an Avaya 4548GT-PWR running RSTP and a Cisco 6500 running Rapid-PVST please.

The 4548GT is an access switch that will be connected to the 6500 core switch over a single 802.1q link. Only the management vlan 1 and a user vlan will be required over the tagged link.

I can't change the RPVST protocol running on the core and I can't configure it to tag it's native vlan; the management vlan 1 (no matter how bad it is).

I've included the relevant config from the 4548GT below. The downlink port on the Cisco core is just a dot1q trunk. Can anyone please let me know if they see problems in relation to STP compatibility?

spanning-tree op-mode rstp

interface fastethernet all
spanning-tree rstp edge-port true

vlan members remove 1 ALL

vlan members add 10 1-46
vlan ports 1-46 pvid 10

interface fastEthernet 1-46
no shutdown
exit

vlan ports 48 tagging tagall
vlan ports 48 pvid 1

spanning-tree rstp port 48 cost 4

interface fastEthernet 48
spanning-tree rstp edge-port false
snmp trap link-status enable
no spanning-tree bpdu-filtering enable
no shutdown
exit

vlan members add 1 48
vlan members add 10 48


Thank you
Brodie

[rameshng]

PVST, PVST+, Rapid PVST+ are Cisco proprietary because running an instance of STP per vlan is a Cisco specific thing.
RSTP is rapid STP.It is an enhancement to STP. RSTP does not work with timers as regular STP (which takes up to 30-50 seconds to converge due to the transtion to all its states) Regular STP can use port-fast for ports not connected to other switches, but all ports connected to other switches need to transition from blocking to listening, learning and finally forwarding.RSTP optimizes this by using P2P lilnks and taking up to only 2 seconds to converge.
RPVST+
Is basically when you mix the two above.You have an instance of rapid STP running per VLAN.
But these two are not interoperable.

When PVST+ is configured, it uses by default, normal STP BPDU’s on VLAN 1 and PVST BPDUs for other VLANs. This allows a PVST+ switch to connect to a switch using IEEE 802.1Q spanning tree as a tunnels for PVST. PVST+ BPDU’s are tunneled across the 802.1Q VLAN region as multicast data. The single STP is addressed to the well-known STP MAC address 01-80-C2-00-00-00. The PVST BPDUs for other VLANs are addressed to multicast address 01-00-0C-CC-CC-CD.
Coming to the Native VLAN:
If you are not tagging the native VLAN from Cisco, then on the ERS4500 side, you need to have the port mode Trunk All and Untag PVID option enabled on the port and PVID on port is native VLAN of Cisco. Else this frames may get discarded.