Proper Trunk/Etherchannel LACP Configuration

Just to make sure, What's your channel-protocol on the cisco port configured as?

 

 

I've always used active/active, it's reccomened...

 

 

Not an end all doc to 802.3ad, but some info.. (from the below link)

 

 

LACP trunking supports four modes of operation, as follows:

 

 

On: The link aggregation is forced to be formed without any LACP negotiation .In other words, the switch will neither send the LACP packet nor process any incoming LACP packet. This is similar to the on state for PAgP.

 

 

Off: The link aggregation will not be formed. We do not send or understand the LACP packet. This is similar to the off state for PAgP.

 

 

Passive: The switch does not initiate the channel, but does understand incoming LACP packets. The peer (in active state) initiates negotiation (by sending out an LACP packet) which we receive and reply to, eventually forming the aggregation channel with the peer. This is similar to the auto mode in PAgP.

 

 

Active: We are willing to form an aggregate link, and initiate the negotiation. The link aggregate will be formed if the other end is running in LACP active or passive mode. This is similar to the desirable mode of PAgP.

 

 

There are only three valid combinations to run the LACP link aggregate, as follows:

 

 

active

 

active

 

Comments- Recommended.

 

 

active

 

passive

 

comments- Link aggregation occurs if negotiation is successful.

 

 

on

 

on

 

comments- Link aggregation occurs without LACP. Although this works, it is not recommended.

 

 

Note: By default, when an LACP channel is configured, the LACP channel mode is passive.

 

 

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a0080094470.shtml

I run all mine (That have channels configured) as active/active. FWIW as a comparison we run some ESX servers with etherchannel too. They have to run on/on because ESX doesn't do LACP... We have no end of troubles with ESX (Because there's no way for the switch and the host to detect cabling errors). 0 problems with BigIP and LACP...

 

 

H

The interfaces are configured in active mode - this is the running config of one interface in the group:

 

 

interface FastEthernet0/21

 

switchport access vlan 100

 

switchport mode access

 

speed 100

 

duplex full

 

udld port

 

channel-group 10 mode active

 

end

 

 

What I'm hearing is that I should be running Active/Active with a Short LTM Timeout. It doesn't appear there is any way to change the Cisco timeout on a 3550?

Nice tip on the ESX servers...

 

 

Can you post your port channel config as well please please?

 

 

Is this working for you? Your switchport mode should be trunk...

Thanks for asking. It seems to be working from my perspective. By that, I mean it is behaving how I would expect. We can shut one port in the channel without disruption, and shutting down both ports triggers VLAN Failsafe. This is the running config of the channel and both ports - we are not using tagged interfaces on the LTM side:

 

 

interface Port-channel10

 

switchport access vlan 100

 

switchport mode access

 

end

 

 

interface FastEthernet0/21

 

switchport access vlan 100

 

switchport mode access

 

speed 100

 

duplex full

 

udld port

 

channel-group 10 mode active

 

end

 

 

interface FastEthernet0/23

 

switchport access vlan 100

 

switchport mode access

 

speed 100

 

duplex full

 

udld port

 

channel-group 10 mode active

 

end

K, you should be fine if you're not looking to tag through the ports.... You may want to set it up as a trunk in case you have a need in the future for multiple vlans etc... That way you won't have to disturb production.. (if indeed it is)..