inconsistent aggregated links

As you can see from the pic below, there is inconsistency in the aggregated links. Sw2 has 3 members in po10 and sw1 only has 2. How will the traffic for vlan1 flows from sw2 to sw1? Will it take ten1/9/3 into its decision to send the frames to sw1? How about sw1 STP, will it block e2/9? Thanks

Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

That depends on type of LAG that is in use (is there control protocol).
With LACP/PAgP Te1/9/3 will go down - reason: link on other end does not talk back.
If LAG is created without control protocol (only with Channel-group ON command) then, most likely, there will be loop introduced to network (for VLAN 1 according to picture). Often mentioned mechanism to introduce loop in network is inconsistent LAG created with ON command (no control protocol for aggregation).
leblancAccountingAuthor Commented:
It is lacp. sw1 has CHANNEL-GROUP 255 MODE ACTIVE. sw2 has CHANNEL-GROUP 255 MODE PASSIVE. Currently sw2 reports that ten1/9/3 is stand alone. But I don't understand is it is still up.
If other side is not configured with LACP intreface Te1/9/3 should not participate in LAG. But it still can be active (and cause problems if STP is not active on port). That's your case, port is still up, looks like placing non active ports in suspended mode is either not default or disabled on that device (if I remember correctly on newer devices standalone-disable is default).

To configure automatic changing port to suspended state if other side is no participating in in LACP:
interface port-channel 255
 port-channel standalone-disable

Open in new window

EtherChannel Member Port States
The port is part of an EtherChannel and can send and receive BPDUs and data traffic.

The port is not part of an EtherChannel. The port can receive BPDUs but cannot send them. Data traffic is blocked.


The port is not bundled in an EtherChannel. The port functions as a standalone data port. The port can send and receive BPDUs and data traffic.

Note When one end of an EtherChannel has more members than the other, the unmatched ports enter the standalone state. In a topology that is not protected from Layer 2 loops by the spanning tree protocol (STP), a port in the standalone state can cause significant network errors. For LACP EtherChannels with Release 12.2(33)SXI3 and later releases, you can enter the port-channel standalone-disable interface configuration mode command to put ports into the suspended state instead of the standalone state. See the “Configuring LACP Port-Channel Standalone Disable” section.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
leblancAccountingAuthor Commented:
This is what I have on sw2. It is a 6509E:

SW2#sh etherchannel sum

Flags:  D - down        P - bundled in port-channel

        I - stand-alone s - suspended

        H - Hot-standby (LACP only)

        R - Layer3      S - Layer2

        U - in use      N - not in use, no aggregation

        f - failed to allocate aggregator


        M - not in use, no aggregation due to minimum links not met

        m - not in use, port not aggregated due to minimum links not met

        u - unsuitable for bundling

        d - default port

        w - waiting to be aggregated

Number of channel-groups in use: 60

Number of aggregators:           62


Group  Port-channel  Protocol    Ports


10    Po10(SU)       LACP      Te1/9/3(I)     Te1/9/4(P)     Te2/9/5(P)   

Open in new window

It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Networking Hardware-Other

From novice to tech pro — start learning today.