VCFlexFabric Shared Uplink Set ( LAG ) to an Juniper EX4500 Virtual Chassi ?

[Fatih Celebi]

Hi,

Does anyone have some experience or info on "gotchas" or similar on how to setup a SUS from Flexfabric to Juniper EX4500 Virtual Chassis ?

I know it maybe a too generic question, but we have setup a LAG on the EX4500 and have trunked it with a lot of VLANS and also have setup them on the SUS in VC but of course it does not seem to work right now. I will investigate further but just wanted to do a quick poll with you out there if there is something you know right now...

Thanks!

[Hongjun Ma · Accepted solution]

I'm not aware of any gotchas with EX Virtual Chassis.

I had customers using VC to Juniper EX and they work fine. For VC, we really don't care if EX is running virtual chassis or not. The only thing VC really cares is LACP if you want to do port bundling and I'm pretty sure Virtual Chassis will send LACP like from one "virtual" switch and that'll keep VC happy.

The best doc you should look at is the ones I wrote to connect VC to HPN IRF or Cisco vPC. Both of them trying to achieve the same thing as Virtual chassis. The beneficial part of doc for you is how to design and connect cables from VC side and how VC config will look like. You'll find both of these docs pointers in my blog. Currently it's the first post in the blog.

[Fatih Celebi]

Woow...Thank you for your amazing quick answer...did not expect that !

Yes, it is working now. We just did forget to disable STP on the LACP LAG group. As soon as we disabled it started to work. I'm glad for that but I really do not understand why STP affects the LAG since VC as I know blocks all BPDU traffic from switches anyway ?

[Hongjun Ma]

good to know. it's weird that STP can affect that. VC will drop any IEEE BPDU and if it's Cisco PVST BPDU, it'll pass to server like regular frames.

I know for cisco switch, you don't have to disable STP on port channel, VC can form LACP bundle without problems. many customers do this way.

but anyway, best practice to connect with VC is to do STP edge and BPDU guard on switch side. Just treat VC as "big" server NIC ports.