Stackwise virtual dual-active detection link question

[timerider33]

Hi! We have two Cat 9500 switches in stackwise virtual mode located in different buildings connected with dark fiber leased from two different ISPs. We still want to plan a separate link for dual-active detection scenario. According to the guide, we need direct ethernet connection between the two Cisco StackWise Virtual switches, but in our case these switches are geographically spread and we can't link them directly in a simple way. The question is, do we need a direct leased line (such as dark fiber) from 3rd ISP to implement fast-hello? Can we use general ethernet VPN (with 10 Mbps bandwith, for example) from the ISP instead? Fast-hello mechanism is not covered in details, if it uses some service protocols that will not run through ISP infrastructure this will not work, but if it is pure L3 it may be an option.

[balaji.bandi]

check the guide lines and Limitation - If that is not met, then you need to go with traditional LAG or trunk betwee Cat 9500 is the option.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/17-9/configuration_guide/ha/b_179_ha_9500_cg/configuring_cisco_stackwise_virtual.html#concept_sjb_byx_31b

Note : if you do not meet the requirement, you will have bigger issue when you put them in production, because of failover scenrios, so better test if you going that route, before you deploy in production.

[Reza Sharifi]

Hi,

So, all you need is a pair of fiber from the service provider to connect the 2 switches together. For the fast-hello connection, all you need is a gig if not, you can use a 10Gig. And no, you can't use VPN for fast-hello. You need a physical connection between the 2 switches.

HTH

[MHM Cisco World]

Currently, there are two mechanisms for detecting a dual-active scenario:

●      Fast Hello

●      Enhanced PAgP <<- this can use if fast hello can not add to stackwise 

MHM

[timerider33]

So as far as I understand, it's not possible to use Fast Hello or Enhanced PAgP through ethernet VPN link. We do need a direct connection via dark fiber on long distance. Thanks for clarification. 

[balaji.bandi]

Sure that is limitation, again SVL is build in the campus, if they are geo location different, what is the goal here  you do not see any advantage of SVL here in this use case,

so go tradtional Port-bundle, or Layer 3 extention, or many other option suited for redundancy.