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Still the Uplink port is in down state on CISCO 3750  after no shutdown command

Posted on 2014-11-22
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Last Modified: 2014-12-16
Hi
We have couple of HP switches and these switches are connected through a fibre link to a Cisco 3750 (One link goes to switch- A and another goes to switch- B)

My predecessor had installed these switches and implemented LACP on these core CISCO 3750 switches please see the attached. The PCs connected to the HP switches are not getting any IP from DHCP, There is no uplink link light coming on Cisco switch A and the uplink port is connected to G3.

I did log into the switch and gave a the following command  and still the port is down state after I  gave no shutdown command.
Switch-Core1# sh ip int brief  and I got the following output and the port GigabitEthernet1/1/3   is down as you can see.
I did  Switch-Core#conf t
Switch-Core1(config) interface GigabitEthernet1/1/3
Switch-Core1(config-if)#no shutdown
Switch-Core1(config-if)#
GigabitEthernet1/0/20  unassigned      YES unset  up                    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  down                    down
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


Any help much appreciated


 Thanks
new-Switch-Connectivity.png
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Question by:lianne143
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by:giltjr
giltjr earned 250 total points
ID: 40460061
Have tried swapping out the cable?

If these are SFP ports, try swapping out with a known good SFP.
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by:lianne143
ID: 40460162
If I connect another fibre uplink that comes from the core to same  HP switch , I can see the link on the HP switch.
See the sh ip int brief , the SFP uplink GigabitEthernet1/1/3   is  down
I think some STP has happened in the network and the  GigabitEthernet1/1/3   is  down , even in spite of saying no shutdown , this interface is not up. So I think if this interface is up , the link betweek HP and core must be working.

Please suggest how to go abt sorting this

thanks
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giltjr earned 250 total points
ID: 40460188
STP will not cause a port not to come active.  If you have a loop the port would still be active and in a blocked status when you look at spanning tree information on which ever switch is the root.

Did you no shut on both switches involved?

Since it seems to have been working, what changes were made when it stopped working?

I'm confused about what you are saying in your last post though.  It seems like you connected a DIFFERENT cable from a DIFFERENT port to a DIFFERENT port and and you can see the link light on DIFFERENT port.

What happens you connect a DIFFERENT cable to the same ports?  

I beleive that you may have a cable or SFP problem, so you need to try to swap out the cable and the SFP's at both nds.
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by:Craig Beck
Craig Beck earned 125 total points
ID: 40460679
With everything connected as you want it can you issue the following commands on the 3750 stack and post the output?

show run int gi1/1/3
show etherchannel summary
show interface transceiver
show log
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by:Otto_N
Otto_N earned 125 total points
ID: 40461764
I agree with giltjr:  The fact that the interface is down/down would indicate a physical problem - In my experience, I always first check if the Tx/Rx fibres aren't swopped - "show interface transceiver" should tell you the optical power levels on the SFP, but only if you have SFP's with the Digital Optical Monitoring (DOM) feature.
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