Multicast issues!

[KatherineTran]

Hi, Ive been troubleshooting a multicast configuration we have deployed today and identified that ACI does not support L3 Out VPC SVI for routing multicast. Is there anyway we can get around this.

Currently the L3Out is spanning some L2 VLANs and has BGP connectivity hence the choice of VPC SVI L3 Out. 

This is the only physical connections we have from 2 border leafs (one each.) Is it possible to configure another L3Out like a sub interface without breaking the existing. I could not find a document. 

Thanks in advance!

[Sergiu.Daniluk]

Hi @KatherineTran 

Since you already have a VPC configured, you cannot reuse the same physical ports as L3 sub-interfaces in another L3Out.

The solution I have in mind for you to reconfigure and avoid disrupting traffic is:

1. shutdown the link from one vPC peer and move the cable to another port. At this point you have the L3Out up and running on the second vPC peer.

2. configure a second L3Out with L3 sub-interfaces. If there are specific subnets configured in the original ExtEPG, then you cannot configure them in the new one so you will have to make some summarization. If the original ExtEPG is with 0.0.0.0/0, then you can configure it in the second one as well.

3. Once the new L3Out is up and running, you can shutdown the remaining vPC link, delete the old L3Out and re-configure the port in the new L3Out.

Stay safe,

Sergiu

[KatherineTran]

Thanks, Sergiu for your reply. To clarify, the VPC is one link on each Border Leaf and we do not wish to take out the resilience. So my understanding is I will need to get another physical link in to get around this caveat?

[Sergiu.Daniluk · Accepted solution]

Hi @KatherineTran 

This is one way to do the job - add another phy link.

Second way - if adding another sfp/cable/etc is not possible, is to migrate from the existing vPC L3Out to individual L3 subinterfaces L3Out with minimal impact as I described above.

Take care

Sergiu