3750 xstack to 6509 change from pagp to lacp

[jmd323232]

Currently, 1 3750 in the stack has 2 ports in pagp etherchannel trunk to 6509.

I want to change it so that each switch in the stack has 1 port in the etherchannel.

The switches are in production. Is there a way to change to lacp that won't result in any loss of connectivity? 

Can I just configure the port on switch 2 as active, plug 1 of the uplinks into that, then reconfigure the port on switch 1 from desirable to active?

Current config

6509

int p37

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan (some vlans)

switchport mode trunk

int g3/37

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan (some vlans)

switchport mode trunk

channel-group 37 mode desirable

int g8/37

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan (some vlans)

switchport mode trunk

channel-group 37 mode desirable

3750

int p1

switchport trunk allowed vlan (some vlans)

switchport mode trunk

int g1/0/1

switchport trunk allowed vlan (some vlans)

switchport mode trunk

channel-group 1 mode desirable

int g1/0/2

switchport trunk allowed vlan (some vlans)

switchport mode trunk

channel-group 1 mode desirable

[vb10]

Hello,

You can't have 2 physical ports in different mode (pagp or lacp) within the same port-channel.

You can create new port-channel and move there ports one-by-one along with changing protocol. During the time, when you will have ports in different port-channels, one of them should be blocked by STP. There still might be short interruption during STP convergence, depends on exact STP protocol used.

[jmd323232]

So just make new portchannels on the 6509 and the 3750 stack. Then
"channel-group (new#) mode active" for the ports on the 6509 and mode
passive on the 3750?

[vb10]

Hello,

Basically, yes. But I suggest you do it in more structure way.

1. Shutdown ports "migrated" first

2. Delete old port-channel config

3. Apply new port-channel config

4. Enable ports

[jmd323232]

What if i setup the new pchannel on both, shutdown one of the links on both ends, moved it to the other switch on the 3750 then added both ends to the pchannel and no shut them? Would that cause a loop? if not, then do the same with the other link. 

[Reza Sharifi]

That can cause a loop or STP will block one of them. I recommend making these changes in a maintenance window as this type of change will usually cause downtime. 

HTH

[jmd323232]

What about this?

1. shutdown one of the two interfaces on each side

2. remove portchannel from second interface that is shutdown.

3. remove portchannel config from active interface.

4. add portchannel to active interface using active mode

5. add portchannel configuration to second interface using active mode