Cross connections between two VSS domain switches(9K Catalyst)

[titusroz03]

Dear All,

We are planning to connect two VSS switches in different domains i.e switch A & B in one domain and switch C & D in another. Users will connect from Access to Switch C(Active stack)  traverse through switch A to connect internet firewall and Switch D is standby for the access switches. I want to achieve resiliency between switches C , D and A,B so if C goes down D should forward the traffic to A.

For this I created cross links between A & D , B & C,but still I am not sure if this cross link is really needed. Can someone clarify if it is needed or can I simply leave with connection C to A and D to B so that resiliency can be achieved  through VSL links.

Also do I need to bring Multiple stack wise virtual domains into this..?

[balaji.bandi]

Hope they all Located in the same Enterprise LAN.

SVL Means 2 Physical in to 1 Logical, you can add N number of links between these Logical switches - but depends on the requirement how much traffic going via this links

Take example you have Access switches  connected to SWITCH C and D -  all traffic transit via CD-AB-FW (is this cross more than 20GB (taking you connnection links are 10GB x 2 = 20GB (if that is suffcient) then 2 connection good enough

yes you can add more links of high resilience - but again at what cost ?

There are number points need to consider if you looking to add more connection between SVL domain to other SVL Domain depends requirement, yes if you have free ports and SFP and cables, you can add them there is no harm. 

is this Layer2 or Layer3 ? Either case all should be bundled in port-channel is good to achieve high availability.

Also do I need to bring Multiple stack wise virtual domains into this..?

SVL only support 2 devices, you have more SVL domain to join, again the principle is same - more can be find here :

Multiple StackWise Virtual domains

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-9000/nb-06-cat-9k-stack-wp-cte-en.html

[titusroz03]

@MHM Cisco World My intention is to create a resillency for switch C if it goes down or C-A link goes down then switch D should be capable of sending the traffic to switch A.

Can I achieve resiliency between if I add the red marked cross link and create L2 port channels between both Domains..?

[balaji.bandi]

Sure that is the requirement - yes that duable (as i mentioned create 1 Port-channel to add links in it).

also check the guide lines when you joining the 2 SVL domains.

[MHM Cisco World]

I dont see anything about use L2 cross connection, what I see is L3 cross connection

MHM