I've been working lately to update the network designs for our various field offices. The first effort is to upgrade spanning tree to 802.1w using cisco's rpvst+. I had not noticed it before, but due to the rapid convergence, i'm now observing that switches with router trunk uplinks which detect TC's are putting the router uplink in blocking mode for about 25 or 30 seconds. If I understand correctly, this is because RSTP is trying to send proposals out the uplinks, and then holding the port in blocking mode until either its forward timer (max age + listening) expires, or it receives an agreement. The routers LAN facing trunks are not running STP at all, and so the lan looses connectivity for much longer than RSTP takes to converge.
Any idea's on how to improve LAN to WAN convergence times? I'm working with about 5,000 switches, so the simpler the better. My router images dont seem to support RSTP, but I'll be double checking that today in the lab.