Troubleshooting dead fiber trunk that is port channeled

[richard.a.adams]

two fiber trunks connect an Intermediate switch (3850 stack) to our Core switch (6500).   They are setup as a port channel  (ON).

one of the links has died  (not connected).  

I have performed "shut"  "no shut"   to no avail.  Still down.

Can someone give me some step by step procedures to fix this?

I do have spare SFP modules and spare fiber patch cables to swap out if necessary.

Please elaborate as I am still a novice at this.

Do I turn off port channel first?   How do you do that?

The command in place is   "channel-group 63 mode on"

To turn it off would I enter  "no channel-group 63 mode on" ????

[Jaderson Pessoa]

Hello,

Could you share to us the configuration of these interfaces on both side?

By the way, check this simple exemple: https://**bleep**ing-it.com/br/artigos/switch-cisco/392-switch-cisco-configurar-link-aggregation

[richard.a.adams]

Core side:

interface GigabitEthernet4/7
description xxxxxxxxxxxxxxx
switchport trunk allowed vlan 1-1005
switchport trunk native vlan 71
switchport mode trunk
ip device tracking maximum 0
channel-group 63 mode on
ip dhcp snooping trust

Intermediate side:

interface GigabitEthernet2/1/1
description xxxxxxxxxxxxxxx
switchport trunk native vlan 71
switchport trunk allowed vlan 1-1005
switchport mode trunk
channel-group 63 mode on
ip dhcp snooping trust

Your link does not work.   "Page cannot be displayed"

[Jaderson Pessoa]

@richard.a.adams ,

nterface GigabitEthernet4/7
description xxxxxxxxxxxxxxx
switchport trunk allowed vlan 1-1005
switchport trunk native vlan 71
switchport mode trunk
ip device tracking maximum 0
channel-group 63 mode on   no channel-group 63 (will remove the ports from bundle)
ip dhcp snooping trust

Intermediate side:

interface GigabitEthernet2/1/1
description xxxxxxxxxxxxxxx
switchport trunk native vlan 71
switchport trunk allowed vlan 1-1005
switchport mode trunk
channel-group 63 mode on    << no channel-group 63 (will remove the ports from bundle)
ip dhcp snooping trust

It is necessary remove it on both side to link works normally without LAG.

[Seb Rupik]

If the link is DOWN/DOWN at both ends, then there is no harm in replacing the cable/ SFP without changing the config.

If you wanted to play it safe, then issue a shutdown and no channel-group 63 mode on on the interface in question. This will simple remove the switchport from the bundle. Configure both ends of this link to use an unused VLAN and no shut . If the link comes shut it back down, restore the original trunk configuration add channel-group 63 mode on back in and no shut the port. It will then be added back to the bundle.

sh etherchannel 63 summary

...should show all links as 'P'

cheers,

Seb.

[richard.a.adams]

I did as you suggested and the link still did not come up.   Guess my next step is to go to the site with spare stuff and make sure connections look good physically and then replace one thing at a time.  

[Seb Rupik]

Yes, the steps suggested were to safely isolate the pair of switchports for inter-switch testing.

As you say the next step is to eyeball the remote end and check SFPs/ fibres, perhaps test connecting it to something local using a patch lead before attempting the infrastructure fibres again.

cheers,

Seb.

[balaji.bandi]

when you no shut do you see any errors or port not come up at all. then looks physical cable, as suggested check the Light, and twist the pair based on the Tx and Rx side.(if you see red light- when you no shutdown the port)

[Leo Laohoo]

Use a visible light to determine if the entire length is broken or not.
If the length is not broken, replace the patch cables at both ends. If still down, replace the optics at both ends.