port authority...

root port - every switch in the diameter has a root port; the port with the least cost path to the root switch

designated port - every switch in the diameter has at least one designated port; it is a port on a LAN segment (non-root port) with the least cost path to the root switch

blocking port - a port which is neither root port nor designated port

alternate port - candidate root ports although currently blocking but close to the root switch and identified by uplinkfast as suitable

forwarding port - just that, forwarding; no other stp activity expected

you're out of your tree...

a disabled port does not participate in spanning tree; it is either administratively down, or faulty... it does not block,  it is down

a blocked port is participating in spanning tree; it blocks, yet receives bpdu's

a port moves to the listening state when determined it has the potential to forward; it is transitioning.  it is not
   sending or receiving frames, and like blocking it is receiving bpdu's but it is not sending bpdu's; it is
   transitioning to the learning state

a port transitions from listening to learning before it gets to forwarding.  in the learning state the port is now
   adding mac's to it's table. it is one step closer to forwarding.  if it loses its potential, it will revert to blocking.

forwarding... the port has made it to the show after the requisite delays in the tranistory states.  it is adding mac addresses to its table, it is sending and receiving frames and bpdu's... it is in the big's...

spanning tree, i do love thee...

my members...

etherchannel configuration...  it's a good idea if both sides match...


interface FastEthernet0/1
 switchport mode trunk
 speed 100
 duplex full
 channel-group 1 mode on
!
interface FastEthernet0/2
 switchport mode trunk
 speed 100
 duplex full
 channel-group 1 mode on
!
interface FastEthernet0/3
 switchport mode trunk
 speed 100
 duplex full
 channel-group 2 mode on
!
interface FastEthernet0/4
 switchport mode trunk
 speed 100
 duplex full
 channel-group 2 mode on

nice way to keep track of membership...


sw2950_01#sh int port-chan 1 | inc Members
  Members in this channel: Fa0/1 Fa0/2
sw2950_01#


sw2950_01#sh int port-chan 2 | incl Members
  Members in this channel: Fa0/3 Fa0/4
sw2950_01#

don't let spanning tree decide root... the root id is the id of the root and the bridge id is the id of this switch... if  the priority of the two is equal, this is the root... if the mac's are the same, this is the root... if it says this is the root, this is the root... if all ports are forwarding, this is the root... how do you like my root...


sw2950_01(config)#spann vlan 50 root primary

sw2950_01(config)#do sh spann vlan 50

VLAN0050
  Spanning tree enabled protocol rstp
  Root ID    Priority    24626
             Address     0009.b752.d780
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24626  (priority 24576 sys-id-ext 50)
             Address     0009.b752.d780
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po2              Desg FWD 12        128.65   P2p
Po1              Desg FWD 12        128.66   P2p

sw2950_01(config)#

and some aggregation up inside..


sw2950_01(config)#do sh int port-channel1
Port-channel1 is up, line protocol is up (connected)
  Hardware is EtherChannel, address is 0009.b752.d781 (bia 0009.b752.d781)
  MTU 1500 bytes, BW 200000 Kbit, DLY 1000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Full-duplex, 100Mb/s, media type is unknown media type
  input flow-control is off, output flow-control is off
  Members in this channel: Fa0/1 Fa0/2

spanning-tree never tires me...

rstp (802.1w) introduced new port roles; among them, discarding.  discarding replaces the
traditional roles of disabled, blocking and listening, leaving only discarding, learning
and forwarding.  discarding is in the active topology as a replacement during the
listening phase of spanning tree but still does not populate mac addresses, just as
listening doesn't in STP. so although discarding has replaced listening, discarding during
the listening phase is considered part of the active topology. this is kind of a silly point because ultimately the role is called discarding yet part of the active topology.  go fish. i guess it's actively discarding...

again, rstp only defines a discarding state from disabled through listening.

alternate and blocked ports in rstp:
An alternate port receives more useful BPDUs from another bridge and is a port blocked.

A backup port receives more useful BPDUs from the same bridge it is on and is a port
blocked.

a port blocked here is important, as opposed to a blocked port.  there are no blocked ports in rstp.

i didn't make this shit up...

spanning-tree song...

spanning-tree very pretty and the bpdu's are sweet,
but the root of the poor spanning, is impossible to eat,

Michael the network cat likes that song... reow
 

STP elects a root bridge (switch) and puts all root bridge interfaces into forwarding state

Each non root bridge (switch) determines which of its ports has the least administrative cost (best) to the root bridge and STP makes that port that switch’s root port.

The switch with the lowest (best) cost  to the root is put in forwarding state.

The lowest cost switch on each segment is the designated bridge (switch) and the interface on that switch is called the designated port.

            The root bridge’s (switch) ports are always in forwarding state and the root switch (bridge) is always the designated bridge on all connected segments.

            The non root bridge root port is always forwarding. This port receives the lowest cost BPDU from the root.

            Each LAN’s designated port is always forwarding and the bridge forwarding the lowest cost BPDU is the segment’s designated bridge (switch)

             All other ports are blocking. No forwarding frames, no receiving frames.

         At first each switch claims to be root by sending BPDU’s that contain:

                 The root bridge ID- a combination switch priority and MAC address, lower number, higher priority

             The cost to reach the root- again the lower, the better

             And it’s own bridge ID

can't we just call a root bridge a root switch instead...

Stinky Toilet Paper...

this is gonna hurt you more than me...
spanning-tree port states... arrrrrrrrrrrrrrgh

after initializing, a switchport always enters the blocking state

blocking:
the port dumps the frames received
dumps frames switched for forwarding from another switch
doesn't learn shit
receives bpdu's

listening:

the port dumps the frames received
dumps frames switched for forwarding from another switch
doesn't learn shit
receives bpdu's

learning:
the port dumps the frames received
dumps frames switched for forwarding from another switch
finally gets off its dead ass and learns addresses
receives bpdu's

forwarding:
receives and forwards frames
forwards frames switched from another port
learns addresses
receives bpdu's

disabled:
doesn't do shit

why? how? wtf...

why hasn't cisco fabricated rj-45 to usb console cables?
so you can go out and spend 40 bucks to buy a 3rd party adapter...

when a root bridge is established, why is its priority 32769?
because of  sys-id-ext 1

how often does spanning-tree send hellos?
every 2 seconds

if you debug spanning-tree you can expect a lot of output at the console, so how do you preempt this?
by issuing the command un all before issuing the command debug spanning-tree... why?
so you can stop the madness by pressing up arrow and enter, to turn it off...

from a telnet session you issue debug spanning-tree... why isn't there any output to the screen?
you haven't issued terminal monitor from privileged-exec mode, that's why...

to accomplish convergence, what states must the ports be in?
blocking and forwarding

and how long does convergence take?
50 seconds

how do you turn off stp to get rid of this 50 second shit on a port?
in interface configuration mode use spanning-tree portfast and the the interface will move to forwarding on linkup