Spanning-tree and PacketTracer - wtf?!

Topology:

D1 is set as the root for VLAN 10,20,100,200 and D2 (upper right) is set as the secondary root. All switches are running rapid-pvst

When I do show spanning-tree vlan 10, it shows a non-existent root with a priority of 1 and a MAC address that doesn't belong to any of the switches.

Further more, for VLAN 10, Switch 0 (lower left) thinks it's RP is Fa 0/2 (to D2), D2 thinks its RP is FA 0/3 (to D1), and D1 doesn't have a RP, all it's port are designated ports, however it's not the root.

I'm probably missing something obvious but I can't figure it out and it's driving me insane.

Find more posts tagged with

Comments

Priston

try updating packet tracer or saving your work and re opening packet tracer

pham0329

saving/closing PT didn't do anything.

The problem was solved once I created SVIs on the access switch (Switch 0 and Switch 1)...which brings me to my next question. Why do I have to create SVIs (10 and 100 on Switch 0, 20 and 200 on Switch 1) for spanning-tree to work correctly.

CCNP11

Packet Tracer was designed for 'NA level studies. It does not know how to handle complex STP configurations. I would caution anyone going for NP against using PT. It's an emulator only, and not a very good one IMO. The best thing you can do is buy some cheap switches off of eBay or find some spares at work. PT can, and most definitely has, mislead students greatly.

As an example...when using etherchannels, assuming the etherchannel is up and configured properly, PT will A) still show the physical interfaces in #show spanning-tree. Only the Port Channel interface will show on a real switch.

the cost for the interfaces, including the PortChannel int, will not decrease. I created an etherchannel from 3 fastethernet interfaces in PT and 'sh spann' revealed 4 interfaces in the output, 3Fas and 1Po, all with a cost of 19. That is completely wrong and that was the last time I attempted to use PT.

PT is a good tool for prospective CCNAs, but for your own good you should leave it with your NA studies.

When I wanted lab time to prep for SWITCH I rented from CCIE4U.com (I have no affiliation) Their racks are designed for CCIE candidates but I just used the 4 3560s in their rack and ignored the routers. It worked very well for me. This is real equipment that will show you real output.