Switching

Hi All,

I would like to connect a cisco stack based on two 3750  to a virtual juniper Ex3300 (backbone)

My question is , do I need to setup spanning tree on the cisco stack or not.

The cisco stack will be connected to a juniper chasis trough 2 ports configured with LAG and port chanel on cisco side.

see the attached screenshot.

Thanks for your reply

The question you should ask yourself is 'would I need to configure spanning-tree if those weren't stack or virtual-chassis?'

A LAG/Po acts as a single link regardless of how many physical links they have.

Usually it's a good idea to enable stp. Prevents you run into issues when people connect cables wrongly intentionally or unintentionally. 

=====

If this worked for you please flag my post as an "Accepted Solution" so others can benefit. A kudo would be cool if you think I earned it.

There is no 'spanning tree 'configuration setup for the moment , my first target is to get the new cisco stack connected to juniper virtual chasis backbone.

From Juniper virtual chasis I had the following result when running command: sh spanning tree bridge.

STP bridge parameters
Context ID : 0
Enabled protocol : RSTP
Root ID : 32768.3c:8a:b0:de:bf:01
Hello time : 2 seconds
Maximum age : 20 seconds
Forward delay : 15 seconds
Message age : 0
Number of topology changes : 0
Local parameters
Bridge ID : 32768.3c:8a:b0:de:bf:01
Extended system ID : 0
Internal instance ID : 0

I'm not a juniper expert, but looks like no spanning tree configured .

From the cisco stack that i want to add to my network to have extra port I got   

Switch#sh spannning tree 

'Switch#No spanning tree instance exists.

and from running conf 

spanning-tree mode rapid-pvst
spanning-tree extend system-id

I have prepared my LAG and Po1 ports to connect both the virtual chasis and cisco stack.

Could you please drive me on the steps of configuring spanning tree when connecting two vendors equipements Juniper and cisco.

Thanks a lot.

parau explained that in your case, the final effect/result is that you are simply connecting two switches with a single cable. There is no loops so stp is not required. Howeever as he further explained, that does not prevent end users from connecting devices that send BPDUS which can result in stp convergence. In case of Juiniper, RST is the better protocol to enable and you would enable the same equivalent for CISCO. However you can also use L3 for the connection. There are some caveats when connecting Juniper and CISCO and to that end Juniper has a complete document on that scenario. Please see attached document.

Attachment(s)

CISCO_and_JuniperSpanningTreeIntegration.pdf   707 KB 1 version

Thank you that document will help me a lot.

"Accepted  Solution"