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Cisco 3850: Adding a new member to an existing port-channel group

pgutierreziii
Level 1
Level 1

Howdy, needing a refresher on this for a project next month. It's been over 10 years since I played with port-channeling. I was wondering if there are any specific steps in adding a new member to an existing port-channel group? Do I just add the interface in shutdown and unshut? Or do I have to shut both Te interfaces on one side and unshut both at the same time? The switches are 3850 Cisco IOS-XE software.  Thanks in advance. 

This is the plan: To add Te1/1/1 of USCASFCLS-3850Access1FA to Te1/0/8 of the CORE switch


USCASFCLS-3850Access1FA#

interface Port-channel1
description PO1-CORE
switchport mode trunk
end

interface TenGigabitEthernet1/1/1   <<< Adding this from the access end
description PO1-CORE-1
switchport mode trunk
channel-group 1 mode active
end

interface TenGigabitEthernet3/1/1
description PO1-CORE-2
switchport mode trunk
channel-group 1 mode active
end

+++++++++ CORE switch +++++++++ 

interface Port-channel1
description Port-Channel-1stFl
switchport mode trunk
end

interface TenGigabitEthernet1/0/8   <<< Adding this from the CORE end
description Port-Channel-1stFl-1
switchport mode trunk
shutdown
channel-group 1 mode active
end

interface TenGigabitEthernet5/0/1
description Port-Channel-1stFl-2
switchport mode trunk
channel-group 1 mode active
end

6 Replies 6

Leo Laohoo
Hall of Fame
Hall of Fame
switchport mode trunk
channel-group 1 mode active

The most important thing is these two commands (in order).  

If the link is not yet up, no need to shut the ports.  

For security purposes, please stop using VLAN 1 for any traffic.

M02@rt37
VIP
VIP

Hello @pgutierreziii 

The main goal here is to ensure that the new interface seamlessly integrates into the port-channel while maintaining consistent settings on both ends of the link...

The first step is to verify the current configuration of the port-channel and its member interfaces. This includes checking the port-channel configuration and the individual interfaces already part of the group. Using commands like show etherchannel summary and show running-config ensures that the existing setup is well-understood and that the new interface will match the required settings.

When configuring the new member interface, it’s essential to ensure that its attributes, such as speed, duplex, and switchport mode, align with those of the existing port-channel. The new interface should be shut down during configuration to prevent any misalignment or traffic issues. The channel-group command is then used to assign the interface to the correct port-channel in the desired mode (e.g., `active` for LACP). Once this configuration is applied, the same steps must be mirrored on the corresponding interface at the other end of the link.

After configuration, the interfaces on both switches are brought back online using the no shutdown command. It is important to monitor the status of the port-channel to confirm that the new member has been successfully added. Command such as show etherchannel summary provide insights into whether the interface is active and correctly bundled within the port-channel.

Finally, it’s important to validate traffic flow and check for errors or mismatches. Using show interfaces on the new member interfaces helps ensure that there are no unexpected drops or errors. If everything is configured correctly and LACP negotiation is successful, the new interface will seamlessly join the port-channel, providing additional bandwidth and redundancy as you looking for...

 

Best regards
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pgutierreziii
Level 1
Level 1

M02@rt37 @Leo Laohoo Thank you both for your replies. I noticed it mentioned I have to have both ends (switches) in shut interface mode. My plan was to shut just one end which would be the interfaces on the CORE switch and add the new member Te1/0/8 and unshut both interfaces from the CORE switch.  Trying to avoid going to the multiple IDF switches during the maintenance. 

If the link is not yet up, no need to shut the ports.  

balaji.bandi
Hall of Fame
Hall of Fame

When you adding new Interface, there is will small convergence time when you bring the interface up part of port-channel you just need same configuration as other interface you configured.

Make sure you running faster STP convergence, as suggested i would always avoided VLAN 1 as native vlan and rather trunk, i take control only allow the VLAN required between switches with trunk allowed vlan XXX (better way of handling).

BB

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pgutierreziii
Level 1
Level 1

Just wanted to get back to everyone. The maintenance went super smooth. Couldn't ask for a better scenario. Thanks all !