Trying to simulate broadcast storm in Packet Tracer and certain things not working

Like the title says, I'm trying to simulate a broadcast storm in Packet Tracer 6.1 and having a few issues.

I've attached a screenshot (can't upload the .pkt file nor can I upload it as a .zip file).

I have four hubs, two of the hubs I have two links to each other with copper cross-over. For some reason that link isn't lighting up green. I'm not why. If I mouse over the hub, the link shows down.

I also have a single link between two of the hubs. For some reason, one is ok, while the other isn't.

2.6 broadcast storm 2.jpg

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Comments

theodoxa

Strange, it almost looks like PT is performing loop prevention on the hubs. Its not quite STP, because there is no apparent root bridge with all its ports forwarding, but it is clearly disabling redundant links and one link that would create a loop.

[EDIT] I don't know if PT supports it or not, but you could try BPDUFilter or the "no spanning-tree vlan <vlan id>" command to disable STP on an IOS switch.

JockVSJock

In Packet Tracer, these are dumb hubs, and I don't think I have the ability to program them.

I can try to swap them with switches and turn off STP. For the redundant links between the switches, should these be in their own VLANs instead of a non-trunked port? The reason I mention this is that you talk about the command "no spanning tree vlan" so is this only pertains to a port or a global command?

theodoxa

JockVSJock wrote: »

In Packet Tracer, these are dumb hubs, and I don't think I have the ability to program them.

I can try to swap them with switches and turn off STP. For the redundant links between the switches, should these be in their own VLANs instead of a non-trunked port? The reason I mention this is that you talk about the command "no spanning tree vlan" so is this only pertains to a port or a global command?

It disables STP for the VLAN. Per my notes, it appears to be able to be used either as a global configuration or interface configuration command. The former should disable STP globally for that VLAN and the latter just on that port.

theodoxa

Just tried it in PT. Once I ran "no span vlan 1" on all the switches, all their ports began forwarding, and...

Switch#sh mac add Mac Address Table

Vlan Mac Address Type Ports
----

1 0007.ec10.1501 DYNAMIC Fa0/3
1 0007.ec10.1502 DYNAMIC Gig1/1
1 0090.0c57.cd03 DYNAMIC Fa0/3
Switch#sh mac add
Mac Address Table

Vlan Mac Address Type Ports
----

1 0007.ec10.1501 DYNAMIC Fa0/3
1 0007.ec10.1502 DYNAMIC Fa0/3
1 000a.f3a0.2d01 DYNAMIC Gig1/1
1 0090.0c57.cd03 DYNAMIC Fa0/3
Switch#sh mac add
Mac Address Table

Vlan Mac Address Type Ports
----

1 0007.ec10.1501 DYNAMIC Gig1/2
1 0007.ec10.1502 DYNAMIC Gig1/1
1 000a.f3a0.2d01 DYNAMIC Gig1/1
1 0090.0c57.cd03 DYNAMIC Fa0/3

0007.ec10.1502 is flapping between Gi1/1 and Fa0/3
0007.ec10.1501 is flapping between Fa0/3 and Gi1/2
etc...

Switch#ping Protocol [ip]:
Target IP address: 192.168.1.255
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 192.168.1.255, timeout is 2 seconds:

Reply to request 0 from 192.168.1.1, 302 ms
Reply to request 0 from 192.168.1.3, 491 ms
Reply to request 0 from 192.168.1.1, 612 ms
Reply to request 0 from 192.168.1.1, 777 ms
Reply to request 0 from 192.168.1.1, 835 ms
Reply to request 0 from 192.168.1.3, 827 ms
Reply to request 0 from 192.168.1.1, 1129 ms
Reply to request 0 from 192.168.1.1, 1231 ms
Reply to request 0 from 192.168.1.1, 1409 ms
Reply to request 0 from 192.168.1.1, 1804 ms
Reply to request 0 from 192.168.1.3, 1930 ms
Reply to request 0 from 192.168.1.3, 1947 ms

The switch replied to its own echo and received its own reply 8 times. It also received switch #3's echo reply 4 times.

mikeybinec

theodoxa wrote: »

Just tried it in PT. Once I ran "no span vlan 1" on all the switches, all their ports began forwarding, and...

0007.ec10.1502 is flapping between Gi1/1 and Fa0/3
0007.ec10.1501 is flapping between Fa0/3 and Gi1/2
etc....

Just wondering how you got to see this

theodoxa

mikeybinec wrote: »

Just wondering how you got to see this

Green Lights on the topology indicate forwarding. You can confirm that no spanning-tree instances exist (STP is disabled) using "show spanning-tree". Use "show mac address-table" to view the CAM table. Run it a few times in succession to see the difference (flapping MAC addresses).

mikeybinec

Yeah, I couldnt get that result..I was doing long pings and etc. They only thing I noticed was the mac address table had more entries

JockVSJock

I've set this up with two switches and have redundant links between the two.

Just wondering, I though I would use this command to turn off STP

no spanning-tree mod pvst

One of the redundant links was still brown/orange color, so I knew that wasn't the correct command...so I googled around and found this command

no spanning-tree vlan 1

Once I did that all links turned green, so I though the previous command would turn off STP, however it looks/feels like that the last command turned off STP. I don't understand what vlan 1 has to do with STP. I though STP was just a default vlan for Cisco switches.

theodoxa

JockVSJock wrote: »
I've set this up with two switches and have redundant links between the two.

Just wondering, I though I would use this command to turn off STP
no spanning-tree mod pvst
One of the redundant links was still brown/orange color, so I knew that wasn't the correct command...so I googled around and found this command

This command would I believe (guessing based on other commands) set the switch back the default STP mode, which is I believe pvst anyways...so I suspect it has no effect at all.

no spanning-tree vlan 1
Once I did that all links turned green, so I though the previous command would turn off STP, however it looks/feels like that the last command turned off STP. I don't understand what vlan 1 has to do with STP. I though STP was just a default vlan for Cisco switches.

This is the correct command. It disables STP on a Per-VLAN basis. In this case, STP would not be running on VLAN 1, but could still be running on other VLANs. On a switch with default VLAN configuration, this would effectively disable STP.