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15
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3850s not talking

Douglas_Turner
Level 1
Level 1

I have two 3850s that are connected via copper. I can connect a device to each switch and can see the switch but I cannot see the other switch or other devices connected to the switch. I know I missed something in the config but can't find it. I am wondering if someone might be able to take a look at it and let me know what I missed. 

Thank you

1 Accepted Solution

Accepted Solutions

Hello
If your connecting these switches via those two ports shown in your config then STP will be blocking the ports as those ports will be receiving BPDUs from each other and such bpduguard will err-disable the ports, so you need either one of two things.

 

1)
Int gig1/0/1
no spanning-tree portfast
no spanning-tree bpduguard enable~

Int gig1/0/48
no spanning-tree portfast
no spanning-tree bpduguard enable

 

 

                           Or

2) 

no spanning-tree portfast bpduguard default


Int gig1/0/1
no spanning-tree bpduguard enable~

Int gig1/0/48
no spanning-tree bpduguard enable

 


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

View solution in original post

5 Replies 5

robert.lorrison
Level 1
Level 1
Are you trying to connect them via the port-channel? If so you need to apply that to the physical interfaces.

I’m assuming Gi1/0/1 and 1/0/48 are your connecting ports, in which case you can try this:

conf t
int g1/0/1
channel-group 10 mode active
int g1/0/48
channel-group 10 mode active

You’ll need to mirror that on the other switch as well, and it might prompt you to disable spanning-tree on the interfaces.

Leo Laohoo
Hall of Fame
Hall of Fame

@Douglas_Turner wrote:
interface GigabitEthernet1/0/1
 description Cargo 3850
 switchport access vlan 190
 spanning-tree portfast
 spanning-tree bpduguard enable
!
interface GigabitEthernet1/0/48
 description Cargo 3850
 switchport access vlan 190
 spanning-tree portfast
 spanning-tree bpduguard enable

WTF.  Are these the two links connected to each other?  

I know why they're not working:  Ports are in error-disable because of BPDU Guard.  

Deepak Kumar
VIP Alumni
VIP Alumni

Hi,

There is some misunderstanding in an attached configuration as:

 

Where is Port-Channel10 is connected?

 

interface Port-channel10
switchport mode trunk
!

 

Where interfaces GIG1/01 and 1/048 are connected?
!
interface GigabitEthernet1/0/1
description Cargo 3850
switchport access vlan 190
spanning-tree portfast
spanning-tree bpduguard enable
!
interface GigabitEthernet1/0/48
description Cargo 3850
switchport access vlan 190
spanning-tree portfast
spanning-tree bpduguard enable

 

If port-channel 10 is connected to 3850s then share the complete configuration of port-channel, member port configuration from both ends.

 

If Gig 1/0/1 & 1/0/48 are connected to Cisco 3850s switches then remove the bpdufilter command from the switch port configuration.

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution if this comment will help you!

Hello
If your connecting these switches via those two ports shown in your config then STP will be blocking the ports as those ports will be receiving BPDUs from each other and such bpduguard will err-disable the ports, so you need either one of two things.

 

1)
Int gig1/0/1
no spanning-tree portfast
no spanning-tree bpduguard enable~

Int gig1/0/48
no spanning-tree portfast
no spanning-tree bpduguard enable

 

 

                           Or

2) 

no spanning-tree portfast bpduguard default


Int gig1/0/1
no spanning-tree bpduguard enable~

Int gig1/0/48
no spanning-tree bpduguard enable

 


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Douglas_Turner
Level 1
Level 1

Thank you all very much. I do apologize I removed ports 1/0/2 thru 1/0/47 from the config to make it smaller. I will be using port 48 on each switch as the connection. I will make the changes to each switch. Thank you all again

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