CCNP Data Center 300-620 Cisco Study Notes

 In a Cisco ACI Multi-Site fabric, when the Inter-Site BUM Traffic Allow option is enabled for a stretched bridge domain, ingress replication on the spines in the source site is used to forward Broadcast, Unknown unicast, and Multicast (BUM) traffic to all endpoints in the same broadcast domain. This method ensures that BUM traffic is replicated and sent out through the spines to the destination sites.

To minimize possible traffic impact during the upgrade of an ACI fabric with 3 APIC controllers and servers dual-homed to pairs of leaf switches configured in VPC mode, the fabric should be upgraded following Option A2. This option involves creating two maintenance groups for the APIC controllers, upgrading one group at a time, and then proceeding with the leaf switches2. This staged approach helps ensure that not all paths are affected simultaneously, thereby reducing the potential for traffic disruption2.

In Cisco ACI fabric, MP-BGP (Multi-Protocol Border Gateway Protocol) is utilized for several purposes, one of which includes the propagation of L3Out (Layer 3 Out) routes within the fabric. Specifically, MP-BGP with VPNv4 address family (AF) is used in the ACI infra VRF (overlay-1 VRF) to distribute external routes from a border leaf to other leaf switches1. This allows for the efficient dissemination of routing information and ensures that all relevant leaf switches are aware of the routes necessary to reach external networks.

References :=

ACI Fabric L3Out White Paper - Cisco1

Configuring ACI Fabric BGP Route Reflectors - Cisco2

ACI Fabric - Underlying protocols - Cisco Community3

Cisco Application Centric Infrastructure Fundamentals, Release 5.3(x)4