Mixed RSTP and STP network, is it still safe to migrate to rstp

[aylaaylaa]

Intially the network was in stp mode.

however, in the process of migrating to rstp mode,

realised we have run rstp mode in both the core switches before all the Distribution Switches and Access Switches are in rstp mode.

Also noticed rstp running, but some vlan are in P2P mode when showing spanning-tree

would there be any impact if new access switches in either stp or rstp mode are being connected in the network, likewise if Distribution switch is being added.

eg: If Distribution switch is in rstp, adding new switch in rstp or stp , what are the impact?

eg: If Distribution switch is in stp, adding new switch in rstp , what are the impact?

Another question,

If continuing to migrate the remaining to rstp, 

how should we be doing it,

would there be any impact in the network.

( so far both the Core had not been restarted)

Appreciate any feedback

[Giuseppe Larosa]

Hello Ay m,

you have probably configured the core switches for Rapid PVST and most of the other switches are still in PVST+.

ensure that the core switches are and will be the root bridge and secondary root bridge for all Vlans.

in RSTP terminology a link between two switches is classified as point to point non edge. This means that a valid RSTP capable neighbor is seen on the link and that the link will use the handshake procedure when a new topology change will happen.

Rapid PVST is backward compatible with PVST+ on a per port basis and so the impact is that your network convergence is still that of a PVST+.

In addition to move all switches to Rapid RVST you need to declare the edge ports (those connecting to end systems) by using the spanning-tree portfast command.

This is necessary to minimize the number of ports / links that are part of the synchronization procedure that gives to RSTP its faster convergence.

see

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

migration from PVST+ to Rapid PVST

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a00807b0670.shtml

Hope to help

Giuseppe