Why a fibre Gigabit Uplink port goes down on a CIsco 3750 as soon as I connect a HP Edge Switch.


We have 2 CISCO 3750 switches and LACP was implemented on these core switches by my predecessors. On the workstation side someone looped two data ports with a single LAN cable. I think STP was enabled on the core switch and it shut down this uplink- GigabitEthernet1/1/3 and GigabitEthernet2/1/3(I think these uplink ports are mirrored in the LACP concept)
I have now removed the LAN cable that caused looping.

I went to each GigabitEthernet interface and gave the following command
Switch-Core1(config) interface GigabitEthernet1/1/3
Switch-Core1(config-if)#no shutdown

Switch-Core1(config) interface GigabitEthernet2/1/3
Switch-Core1(config-if)#no shutdown

Please see below from the configuration in the sh ip int brief
Now both the uplink ports are up
GigabitEthernet1/0/21  unassigned      YES unset  down                  down
GigabitEthernet1/0/22  unassigned      YES unset  down                  down
GigabitEthernet1/0/23  unassigned      YES unset  down                  down
GigabitEthernet1/0/24  unassigned      YES unset  up                    up
GigabitEthernet1/1/1   unassigned      YES unset  up                     up
GigabitEthernet1/1/2   unassigned      YES unset  up                     up
GigabitEthernet1/1/3   unassigned      YES unset  up                     up
GigabitEthernet1/1/4   unassigned      YES unset  up                     up
Te1/1/1                unassigned      YES unset  down                  down
Te1/1/2                unassigned      YES unset  down                  down
GigabitEthernet2/0/1   unassigned      YES unset  up                    up
GigabitEthernet2/0/2   unassigned      YES unset  up                    up
GigabitEthernet2/0/3   unassigned      YES unset  up                    up
GigabitEthernet2/0/4   unassigned      YES unset  down                  down
GigabitEthernet2/0/5   unassigned      YES unset  up                    up
GigabitEthernet2/0/6   unassigned      YES unset  down                  down
GigabitEthernet2/0/7   unassigned      YES unset  down                  down
GigabitEthernet2/0/8   unassigned      YES unset  up                    up
GigabitEthernet2/0/9   unassigned      YES unset  up                    up
GigabitEthernet2/0/10  unassigned      YES unset  down                  down
GigabitEthernet2/0/11  unassigned      YES unset  down                  down
GigabitEthernet2/0/12  unassigned      YES unset  down                  down
GigabitEthernet2/0/13  unassigned      YES unset  down                  down
GigabitEthernet2/0/14  unassigned      YES unset  up                    up
GigabitEthernet2/0/15  unassigned      YES unset  up                    up
GigabitEthernet2/0/16  unassigned      YES unset  up                    up
GigabitEthernet2/0/17  unassigned      YES unset  up                    up
GigabitEthernet2/0/18  unassigned      YES unset  up                    up
GigabitEthernet2/0/19  unassigned      YES unset  down                  down
GigabitEthernet2/0/20  unassigned      YES unset  up                    up
GigabitEthernet2/0/21  unassigned      YES unset  down                  down
GigabitEthernet2/0/22  unassigned      YES unset  up                    up
GigabitEthernet2/0/23  unassigned      YES unset  down                  down
GigabitEthernet2/0/24  unassigned      YES unset  up                    up
GigabitEthernet2/1/1   unassigned      YES unset  up                     up
GigabitEthernet2/1/2   unassigned      YES unset  up                     up
GigabitEthernet2/1/3   unassigned      YES unset  up                     up
GigabitEthernet2/1/4   unassigned      YES unset  up                     up
Te2/1/1                unassigned      YES unset  down                  down
Te2/1/2                unassigned      YES unset  down                  down
Port-channel1          unassigned      YES unset  down                  down
Port-channel2          unassigned      YES unset  down                  down

Before the looping had happened the blue cable was connected to the HP edge switch as shown in the diagram and when the Gigabit Fibre uplink on the core went down, I had removed the blue cable.
Now after making both the GigabitEthernet1/1/3 and GigabitEthernet2/1/3 ports UP, I connected the blue cable back to the HP edge switches and as soon as I connect the blue cable again the GigabitEthernet1/1/3 and GigabitEthernet2/1/3 port on the core switch goes down. No work stations are connected to the HP Edge switches.

I don’t know why the Gigabit ports on the core switch are shutting down and not sure what is happening, Please let me know if you need more information. Any help to sort this much appreciated.

Thanks in advance
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Don JohnstonInstructorCommented:
Without seeing the configs for the switches we can only make guesses.

But I would start with a spanning tree incompatibility issue.  Cisco and HP default to two different (and incompatible) spanning tree protocols. If the switches aren't configured to use a compatible STP (802.1s) then all bets are off as for predictable behavior.

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Zephyr ICTCloud ArchitectCommented:
Besides Don Johnston's advice about STP, which is very good advice and there's even a document about it ... Maybe there would be something useful in the log of the Cisco switches?

Can you do a "sh log" and post it here ...
lianne143Author Commented:
Sure I will post the "sh log"

Also we have another 3 hub rooms, the Core and HP are connected  in the similar way as shown in the network connectivity diagram, and they are up and running without any issues.
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lianne143Author Commented:
Please see the "sh log" on the core switch test attached , not sure as why  it is showing *Jul 28 15:48:05 , I was enabling the gigabit uplink port on Core yesterday and was connecting the HP Edge. It is not showing yesterdays date at all. Looks like the logging is not enabled. Please suggest how to go about.
Don JohnstonInstructorCommented:
Without the configs and some more details as to which ports on which switch connect to where, there's really no way to troubleshoot this.
lianne143Author Commented:
Please let me know will a  "sh run" output on both the switches be ok. In case if you need more information, please let me know the commands that  I need to issue on the switches and any other details that you require.
Don JohnstonInstructorCommented:
Yes. That will be sufficient.

And don't forget to include which ports on which switches connect to the other switches.

lianne143Author Commented:

Please find the attached "sh run" config on both Core and a working Lan room 1, with a similar type of connection.

LAN room 1
HP Switch-1 Fibre uplink port 48S is connected to Cisco GigabitEthernet1/1/1 on the core switch-Master
HP Switch-2 Fibre uplink port 48S is connected to Cisco GigabitEthernet2/1/1 on the core switch- Secondary

Port 46T on HP Switch 1 and Port 45T on HP Switch 2 are looped with Blue cable.

Daniel SheppardSenior Network Analyst - Core & PerimeterCommented:
You can't do distributed LACP (As your diagram suggests).  That said, I don't see your port channels assigned to any ports in the config for the trunks to the LAN switches.

Can you post: "show spanning-tree mst configuration"?
Don JohnstonInstructorCommented:
Multi-chassis etherchannel is not supported on your HP switches.  All links must terminate on the same HP switch.
lianne143Author Commented:
Thanks, please see the attached the "show spanning-tree mst"
Daniel SheppardSenior Network Analyst - Core & PerimeterCommented:
What about a show spanning-tree on the HP's?
lianne143Author Commented:
Please see the attached the HP Switches spanning tree of a working LAN room 1
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