RSTP vs STP port States

The goal of RSTP is to improve STP convergence. The first step in achieving this was to deprecate some of the 802.1D port states.

Below is a table showing the three port states for RSTP compared to the five ports states of 802.1D STP.

Administrative State	STP State (802.1D)	RSTP State (802.1w)
Disabled	Disabled	Discarding
Enabled	Blocking	Discarding
Enabled	Listening	Discarding
Enabled	Learning	Learning
Enabled	Forwarding	Forwarding

Default STP(Spanning-Tree Protocol) port costs

Rehashing STP at the moment for CCIE studies and thought I'd make a quick note about the default STP port costs and how they've evolved with link speed increases over time.

Things to note with the table below:

The default costs used by Catalyst switches correspond to the 802.1D-1998 version of the standard if PVST(Per-Vlan Spanning-Tree) or Rapid-PVST(Rapid Per-Vlan Spanning-Tree) are used.

If MSTP (802.1s) is used then Catalyst switches use the default costs that correspond to the 802.1D-2004 version.

Just to make things a little more confusing PVST and Rapid-PVST can be forced into using 802.1D-2004 default port costs via the 'spanning-tree pathcost method long' global configuration command. By default PVST and Rapid-PVST use 'spanning-tree pathcost method short' which causes the switch to us the older revision of the costs(802.1D-1998).

Juniper by default uses the 802.1D-2004 default port costs when either RSTP or MSTP is enabled on its switching equipment.

Port Speed	Pre-802.1D-1998 Cost	802.1D-1998 Cost*	802.1D-2004 Cost**
10Mbps	100	100	2000000
100Mbps	10	19	200000
1000Mbps(1Gbps)	1	4	20000
10000Mbps(10Gbps)	1	2	2000

* Cisco Catalyst default for PVST and Rapid-PVST
** Juniper default for RSTP\MSTP & Cisco Catalyst default for MSTP