Cisco 2950 to Juniper EX4200 problems

[Nils Sandborg]

I have a lot of problems with the connection between our Cisco 2950 and Juniper EX4200.

We got two different types of connection, two swtiches with LAG (LACP) and three switches with standard Trunk (STP).

The Problem:

If i connect a new switch to the EX4200, both LAG-interfaces goes down with the following message in the cisco-log:

%PM-4-ERR_DISABLE: channel-misconfig error detected on Po1, putting Gi0/1 in err-disable state

: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po1, putting Gi0/2 in err-disable state

This does not always happen, maybe 20-40% of the times i connect a new swtich or move a switch from a port to another.

This happens reglardless if i have the EX4500 connected or not.

Look on the attached file for setup/conf.

[sharonsa]

You can test communication between Cisco and Juniper devices

at this online lab-

http://www.sharontools.com/online-lab/

[Peter Costin]

Regarding the Juniper Ex 4200 to Cisco 2950 Etherchannel/Aggregate Ethernet LACP issue, the following settings worked in my environment:

On the Juniper EX4200 Aggregate Ethernet interface (ae0):

aggregated-ether-options {

      lacp {

        passive;

        periodic slow;

    }

}

On  the 2950 switch, for each Etherchannel member port:

channel-group mode active

Essentially, this is forcing the Juniper EX4200 to wait for the Cisco 2950 to initiate LACP.