Why 2 interface are used in stackwise virtual link

[HimanshuDwivedi12117]

In Stackwise Virtual Link on 3850 XS. We use 2 interface on both the Switches for configuring Stackwise Virtual Link and 1 interface for Dual Active Detection. Can Any 1 explain why 2 interface are configured in this stacking system?

If we configure only 1 interface as Stackwise Virtual will stack work?

[marce1000 · Accepted solution]

 Ref : https://www.cisco.com/c/dam/en/us/products/collateral/switches/catalyst-3850-series-switches/q-and-a-c67-738577.pdf

 >...

 Q What are SVL best practices and
recommendations?
A Following are recommended Cisco SVL best practices:
  >...
            • Minimum of two SVL connections are recommended for
            better redundancy and load sharing.
 >....

 M.

[balaji.bandi · Accepted solution]

YES / NO - single should work, that is not best practice, if that link break you have split brain scenario, so suggest always SVL should 2 Link along with 1 DAD link. that is the best practice, unofficially you can do many ways, that is not supported.

[HimanshuDwivedi12117]

In case DAD not configured what will be the effect?

[balaji.bandi]

DAD itself give self explanatory, Dual Active Detection - this detects if both go active and take action.

As i mentioned in the original, as long as there i no Link break in theory all should work expected.

But in real world we can not take as risk even .1% - so suggest always best practice as suggested.