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QID:S1 question 3
#1
Hello,
    I believe it will be useful for me to describe this Testlet and possibly of benefit to others as well (that would please me).

Hear are the reasons I think SW-C has implemented PVST+:

1. Catalyst switches run in 'pvst' mode natively and do not (ever to the best of my understanding, at least with current switches) implement pure IEEE 802.1D for either IOS or CatOS.  This is fairly well documented.  The entire purpose of PVST+ was/is to allow interaction with non Cisco switches running a single STP instance over a dotq trunk.  PVST+ does generate ieee BPDUs (802.2 llc header with ssap and dsap set to 0x42 muticast to 0180.c200.0000) for interoperability (context dependant), but it does not 'implement' a single spanning tree instance for all Vlans. 

2. SW-B is a Cisco switch - the OUI is listed as such on the ieee site.  Even though one can't look that up during the exam, it is none the less a matter of public record and as such does qualify the information presented.

3. Extended System ID  - the priority of 24586 suggests that the VID has been added to 24576 (0x6000) for Vlan 10. This is commonly due to issuing 'spann vlan x root primary',  given that the current root is not equal or less than 24,576 (plus VID); in which case local bridge priority is set to 4096 lower than the current root (if I'm not mistaken).

4. Vlan  Root  -  SW-B would be the root for Vlan  1 (rather than Vlan 10) if it were running a single STP for all Vlans.  See URL below and console examples that follow.

http://www.cisco.com/en/US/docs/ios/12_1...#wp1020686


-----------------------------------------------------------------
------------------------------------------------------------------
Example 1:
P2p Peer(STP)  running in 'pvst mode'.  SW-B is a Catalyst switch
------------------------------------------------------------------
Example 2:
Output of the show spanning-tree command on SW-C matching question 3 Testlet (differing MAC addresses).  Same devices as setup for example 1.  SW-B assumes STP root for Vlan 10 due to execution of the 'spanning-tree vlan 10 root primary' command.
------------------------------------------------------------------
Example 3:
Output of the show spanning-tree on SW-C  with Vlan 1 native on trunk links.  SW-B is non Catalyst (other vendor) HW switch running IEEE 802.1D.  SW-B assumes STP root for Vlan 1 with default STP  priority (32,768) due to exclusion of an EX System ID in composite value (and not lowest MAC as tiebreaker).  SW-A is the root for Vlans 10 and 20 due to lower MAC address
------------------------------------------------------------------
Example 4:
Output of the show spanning-tree on SW-C  with Vlan 10 native on trunk links.  SW-B is non Catalyst (other vendor) HW switch running IEEE 802.1D.  SW-B assumes STP root for Vlan 1 with with default STP  priority (32,768) due to exclusion of an EX System ID in composite value (and not lowest MAC as tiebreaker).  SW-A is the root for Vlans 10 and 20 due to lower MAC address
------------------------------------------------------------------
------------------------------------------------------------------







######################
Example 1:
P2p Peer(STP)  running in 'pvst mode'.  SW-B is a Catalyst switch
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> begin example 1
SW-C#show cdp neighbor | begin Device ID
Device ID            Local Intrfce        Holdtme  Capability    Platform  Port ID
SW-A                Fas 0/1              123            S I      WS-C2950C-Fas 0/2
SW-B                Fas 0/2              179          R S I    WS-C3550-4Fas 0/2
SW-C#
........................................verify SW-C has two Cisco peers
SW-C#show spann vlan 10 | begin Interface
Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Altn BLK 19        128.1    P2p
Fa0/2            Root FWD 19        128.2    P2p Peer(STP)

SW-C#
........................................STP output matching question 3 on the Testlet

SW-C#show tech | include spanning-tree mode
spanning-tree mode rapid-pvst
SW-C#
........................................verify the local switch is running Rapid PVST(+) mode

SW-C#telnet 10.1.1.2
Trying 10.1.1.2 ... Open

SW-B>en
Password:
SW-B#show tech | in spanning-tree mode
spanning-tree mode pvst
SW-B#

........................................verify the remote switch listed as " P2p Peer(STP)" has implemented PVST(+)
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> end example 1


######################
Example 2:
Output of the show spanning-tree command on SW-C matching question 3 Testlet (differing MAC addresses).  Same devices as setup for example 1.  SW-B assumes STP root for Vlan 10 due to execution of the 'spanning-tree vlan 10 root primary' command.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> begin example 2

SW-C#show spann

VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32769
            Address    000a.8a0c.0800
            Cost        19
            Port        1 (FastEthernet0/1)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -----------------------
Fa0/1              Root FWD 19        128.1    P2p
Fa0/2              Desg FWD 19        128.2    P2p Peer(STP)



VLAN0010
  Spanning tree enabled protocol rstp
  Root ID    Priority    24586
            Address    0013.c375.a500
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32778  (priority 32768 sys-id-ext 10)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -----------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p Peer(STP)



VLAN0020
  Spanning tree enabled protocol rstp
  Root ID    Priority    32788
            Address    000a.8a0c.0800
            Cost        19
            Port        1 (FastEthernet0/1)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32788  (priority 32768 sys-id-ext 20)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -----------------------
Fa0/1              Root FWD 19        128.1    P2p
Fa0/2              Desg FWD 19        128.2    P2p Peer(STP)


SW-C#

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> end example 2


######################
Example 3:
Output of the show spanning-tree on SW-C  with Vlan 1 native on trunk links.  SW-B is non Catalyst (other vendor) HW switch running IEEE 802.1D.  SW-B assumes STP root for Vlan 1 with default STP  priority (32,768) due to exclusion of an EX System ID in composite value (and not lowest MAC as tiebreaker).  SW-A is the root for Vlans 10 and 20 due to lower MAC address
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> begin example 3
SW-C#show spann

VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32768
            Address    0026.f2ff.3273
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -------------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p Peer(STP)



VLAN0010
  Spanning tree enabled protocol rstp
  Root ID    Priority    32778
            Address    000a.8a0c.0800
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32778  (priority 32768 sys-id-ext 10)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -------------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p



VLAN0020
  Spanning tree enabled protocol rstp
  Root ID    Priority    32788
            Address    000a.8a0c.0800
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32788  (priority 32768 sys-id-ext 20)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -------------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p


SW-C#
SW-C# show interface trunk

Port        Mode            Encapsulation  Status        Native vlan
Fa0/1      desirable        802.1q        trunking      1
Fa0/2      desirable        802.1q        trunking      1

Port        Vlans allowed on trunk
Fa0/1      1-4094
Fa0/2      1-4094

Port        Vlans allowed and active in management domain
Fa0/1      1,10,20
Fa0/2      1,10,20

Port        Vlans in spanning tree forwarding state and not pruned
Fa0/1      none
Fa0/2      1,10,20
SW-C#

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> end example 3

######################
Example 4:
Output of the show spanning-tree on SW-C  with Vlan 10 native on trunk links.  SW-B is non Catalyst (other vendor) HW switch running IEEE 802.1D.  SW-B assumes STP root for Vlan 1 with default STP  priority (32,768) due to exclusion of an EX System ID in composite value (and not lowest MAC as tiebreaker).  SW-A is the root for Vlans 10 and 20 due to lower MAC address.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> begin example 4
SW-C(config-if)#do show span

VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32768
            Address    0026.f2ff.3273
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -----------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p Peer(STP)



VLAN0010
  Spanning tree enabled protocol rstp
  Root ID    Priority    32778
            Address    000a.8a0c.0800
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32778  (priority 32768 sys-id-ext 10)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -----------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p



VLAN0020
  Spanning tree enabled protocol rstp
  Root ID    Priority    32788
            Address    000a.8a0c.0800
            Cost        19
            Port        2 (FastEthernet0/2)
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32788  (priority 32768 sys-id-ext 20)
            Address    000d.ed5f.f800
            Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
            Aging Time  300 sec

Interface          Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- -----------------------
Fa0/1              Altn BLK 19        128.1    P2p
Fa0/2              Root FWD 19        128.2    P2p


SW-C(config-if)#
SW-C(config-if)# do show int trunk

Port        Mode            Encapsulation  Status        Native vlan
Fa0/1      desirable        802.1q        trunking      10
Fa0/2      desirable        802.1q        trunking      10

Port        Vlans allowed on trunk
Fa0/1      1-4094
Fa0/2      1-4094

Port        Vlans allowed and active in management domain
Fa0/1      1,10,20
Fa0/2      1,10,20

Port        Vlans in spanning tree forwarding state and not pruned
Fa0/1      none
Fa0/2      1,10,20
SW-C(config-if)#do show spann incon

Name                Interface                Inconsistency
-------------------- ------------------------ ------------------

Number of inconsistent ports (segments) in the system : 0

SW-C(config-if)#

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> end example 4
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#2
Hello,

I can only say that I took and passed the test based upon the instructions given in this testlet and I got like a 900 score.  I think your question is valid but I am not sure as to the answer.

~J
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