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StackWise Virtual Port Requirements IR/DR Collapsed Core Configuration

Thank you for looking in.


  I'm reviewing the port requirements for StackWise Virtual and want to know the number of ports required for this configuration type.

  The network design is a basic IR/DR collapsed core as depicted in the attachment.  From my review this configuration will require SVL and DAD connections.  Are these in addition to the normal etherchannel connection between the two DR's?


My Estimated requirement:

2 Port SVL connection

1 Port DAD connection

2 Port Etherchannel for trunking between devices.


  For a StackWise configuration between two 9400's acting as IR/DR's does the SVL replace the Etherchannel or do I have to have five cables as the minimum configuration for this technology?



Giuseppe Larosa
Hall of Fame Master

Hello @davsnet2000 ,

Cat 9400 SVL =  Cat 6500 / 6800 VSS


My Estimated requirement:

2 Port SVL connection

1 Port DAD connection

>>>2 Port Etherchannel for trunking between devices.


A single port-channel multichassis can be used to connect access layer devices The SVL pair act as a single entity like VSS


the DAD link could be low speed as it is just needed to avoid active / active scenario when SVL etherchannel fails.


the two ports for SVL should be as fast as possible like for example 40GE or you can use ports taken from different blades same position  


Hope to help



Can the SVL be 10GB or 1GB?  I'm old school Cisco.  I never got to play with VSS.  I did install the first Nexus nodes in the West Coast server farm in 2014, but since then it's been static networks.

Hello @davsnet2000 ,

I need to review my answer


You would need two VSS one per main site and one per DR site so you need 4 C9400 chassis


SVL Links need to be very fast because in some cases traffic can need to go between chasssis.


the DAD can be a GE because it is used just to know if the other chassis is alive.



if you use a single SVL pair you have a single site .


Hope to help





VIP Guru

Not sure what kind of DR here, is this DR for access switch to connect different Stackwise virtual domain, or they operate in different.


some guide lines :  (they need to 2 different domain of stackwise virtual) - since only 2 device can participate in stackwise virtual


Hope this helps you, or if this is not the case explian more about your DR.



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I'm preparing to upgrade current L3 4506's.  The 4506 like it shows in the diagram act as a Inner Router/Distro Router.

  My apologies I didn't identify the WAN connections.  In the current network the 4500's "Collapsed Core Layer" connect to our Access Switches below and to Firepower firewalls above.  There are no outer routers.

  It has been recommended to me for our network to configure our 9400's in a Stackwise Virtual configuration.  I've been managing a small network for 7 years that has been an old school spanning tree, hsrp  network.

  For this EOL upgrade I wanted to upgrade our network to the latest technologies, but due to it's size and no routing protocols it was recommended to me by a Cisco Sales rep I used to work with at the Server Farm to go to Stackwise Virtual.

  I don't want to burden my sales rep friend with all my questions so I've started researching on my own.  I understand StackWise.  We installed it when I was working in the server farm.  In addition to the SF we had four large sites that we took care of.

  I didn't realize that StackWise has expanded above the Access level so I'm playing catchup.