Cisco Packet Tracer Student STP

aryztaryzt Posts: 6Member ■□□□□□□□□□
s!AqP8uq1kzWu1j3jUmmx02m3m5_TF


hye, i got problem with my work. i already work on the cost of the port and the priority of the switch but seem not working. i want g1/1 on LSW5 to be blocked but now i only got g1/1 on LSW6 blocked. and this also can only use one vlan 1.

here is spanning-tree

LSW3
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0001.649C.8A63
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 1 (priority 0 sys-id-ext 1)
Address 0001.649C.8A63
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20


Interface Role Sts Cost Prio.Nbr Type
---- ---


Gi1/1 Desg FWD 4 128.2 P2p
Gi0/1 Desg FWD 100 128.1 P2p


LSW2

VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0001.649C.8A63
Cost 4
Port 2(GigabitEthernet1/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0001.42AB.E01D
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20


Interface Role Sts Cost Prio.Nbr Type
---- ---


Gi0/1 Desg FWD 4 128.1 P2p
Gi2/1 Desg FWD 19 128.3 P2p
Gi1/1 Root FWD 4 128.2 P2p


LSW1

VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0001.649C.8A63
Cost 8
Port 2(GigabitEthernet1/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 00D0.9712.D092
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20


Interface Role Sts Cost Prio.Nbr Type
---- ---


Gi0/1 Altn BLK 100 128.1 P2p
Gi2/1 Desg FWD 100 128.3 P2p
Gi1/1 Root FWD 4 128.2 P2p


LSW4
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0001.649C.8A63
Cost 27
Port 2(GigabitEthernet1/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 4097 (priority 4096 sys-id-ext 1)
Address 0060.47CC.E93D
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20


Interface Role Sts Cost Prio.Nbr Type
---- ---


Gi1/1 Root FWD 4 128.2 P2p
Gi2/1 Altn BLK 100 128.3 P2p
Gi0/1 Desg FWD 19 128.1 P2p


LSW5

VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0001.649C.8A63
Cost 23
Port 3(GigabitEthernet2/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0060.470B.A157
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20


Interface Role Sts Cost Prio.Nbr Type
---- ---


Gi1/1 Desg FWD 100 112.2 P2p
Gi2/1 Root FWD 19 128.3 P2p
Gi0/1 Desg FWD 4 128.1 P2p


LSW6

VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0001.649C.8A63
Cost 46
Port 1(GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 8193 (priority 8192 sys-id-ext 1)
Address 0001.647E.4184
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20


Interface Role Sts Cost Prio.Nbr Type
---- ---


Gi0/1 Root FWD 19 128.1 P2p
Gi1/1 Altn BLK 100 128.2 P2p

Comments

  • WastedHatWastedHat Posts: 130Member
    Can you post a topology diagram?
  • aryztaryzt Posts: 6Member ■□□□□□□□□□
    how can i insert the photo? i can only insert image url....icon_sad.gif
  • aryztaryzt Posts: 6Member ■□□□□□□□□□
    [IMG]file:///C:/Users/user/OneDrive/Pictures/Screenshots/aryzt.png[/IMG]
  • aryztaryzt Posts: 6Member ■□□□□□□□□□
  • WastedHatWastedHat Posts: 130Member
    I don't think there is an easy way to do it.


    On the g1/1 link you're asking about: LSW5 is advertising a much lower root cost on that link, that is why it is fowarding and LSW6 is blocking. If you want LSW5 to block on that port it needs to advertise a higher root cost to LSW6. (try increasing the cost on LSW5's root port)

    At the moment LSW5 is in the root path for two other switches, so the bottom half of the STP topology will be very different if you want that port to block.


    Another thing to note, changing the port priority wont make any difference here. It is used when switches have multiple connections to each other with equal cost.
  • aryztaryzt Posts: 6Member ■□□□□□□□□□
    Ouh I see..thanks....by the way let say if there are 3 switches connected and form triangle...then 1 switch is selected as bridge root...is there possible for one of the bridge root to be blocked?
  • WastedHatWastedHat Posts: 130Member
    It's not possible, all of the ports on a root switch will always be Designated ports so they will always be forwarding. Every other switch directly connected to the root bridge will have root ports on those links.


    It was a good idea to learn from a 3 switch topology, keep it simple to begin. There are a lot of examples that teach you STP with a 4 switch topology like this:

    https://labnario.files.wordpress.com/2013/04/stp-topology-1.png


    If you haven't seen that before look for some videos or labs online, you can learn a lot about STP with that topology.
  • WastedHatWastedHat Posts: 130Member
    Also you can make a topology with only 2 switches. But add 2 links between them like g1/1 and g1/2 and leave the cost at default.

    Now changing the port priority will effect the switch on the other side.
  • aryztaryzt Posts: 6Member ■□□□□□□□□□
    I also think that way...but my lecturer said it's a way to do it...and I ask "is it using ENSP or Packet Tracer" and he said both also can...that's why I asking because he want us to find ourselves...
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