Private VLANs (PVLANs) are specifically designed to provide Layer 2 isolation between ports within the same broadcast domain or VLAN. They can create isolated ports that cannot communicate with each other, which is the precise requirement described. VRF-Lite operates at Layer 3, SGTs are for macro-segmentation and policy, and Port Security controls MAC address access but does not prevent communication between authorized hosts on the same VLAN.

The EXSTART/EXCHANGE state indicates that the routers are attempting to exchange Database Description (DBD) packets. A common cause for stalling in this state is an MTU mismatch. OSPF DBD packets are large, and if one interface has a lower MTU, these packets may be dropped, preventing the adjacency from progressing. While other options can cause adjacency failures, they typically result in different states (e.g., INIT for ACL blocks).

Cisco Performance Routing (PfR) is designed for this exact scenario. It provides intelligent, application-aware path control based on performance metrics (like loss, delay, jitter) and policies. It can monitor both paths and dynamically steer specific application traffic (like video streams) based on defined policies and real-time link performance, offering far more granularity than simple metric manipulation or static tracking.

In Cisco SD-Access, the Edge Node (EN) — typically a fabric edge switch — is responsible for classifying packets entering the fabric. It queries ISE for policy (SGT) and then encapsulates the traffic with a VXLAN header that includes the Scalable Group Tag (SGT). This SGT is carried in-line with the packet across the fabric, enabling policy enforcement at the egress EN without dependency on the source IP address.

Within a BGP confederation, the AS_PATH contains sequences of member AS numbers (sub-ASes) enclosed in parentheses. The standard BGP best path algorithm counts the length of the AS_PATH, but confederation segments (the parts in parentheses) are typically not counted in the AS_PATH length calculation when the decision is made within the confederation. Therefore, prepending within a confederation may not have the intended effect on internal confederation peers.

In a VXLAN EVPN fabric, VTEPs use MP-BGP (EVPN address family) to exchange host reachability information (MAC, IP, and associated VNI). A BGP Route Reflector (RR) allows all VTEPs to peer with it rather than establishing a full mesh of iBGP sessions, significantly simplifying scalability. The RR reflects EVPN routes, such as Type 2 (MAC/IP), between VTEPs, enabling end-host learning across the fabric.

Cisco ACI Multi-Site is designed specifically for extending consistent network and security policies across multiple ACI fabrics, which can be deployed in on-premises data centers and in public clouds (like AWS, Azure, GCP). It provides encrypted intersite connectivity (using IPsec) and maintains centralized policy management through the Multi-Site Orchestrator, making it transport-agnostic and ideal for secure hybrid cloud segmentation.

In PIM-SM, a router expecting to receive traffic for a multicast group will send PIM Join messages toward the RP. If a router is configured with an RP address that points to itself (and it is not the actual RP), it will send Joins to its own address. It will never receive traffic from the real RP, as it’s not looking in the correct direction. Therefore, it will prune off the path to any actual source and fail to forward traffic to downstream receivers.

The Cisco QoS Baseline model (and related models like the 4/5/8-Class model) assigns Interactive Video (or Multimedia Streaming) to the AF4 class. Specifically, AF41 (DSCP 34) is the recommended marking for guaranteed-priority video traffic. This class is typically given a minimum bandwidth guarantee with priority queuing (like Low Latency Queuing – LLQ) to ensure timely delivery and minimize jitter, which is critical for interactive video applications.

Private VLANs (PVLANs) are specifically designed to provide Layer 2 isolation between ports within the same broadcast domain or VLAN. They can create isolated ports that cannot communicate with each other, which is the precise requirement described. VRF-Lite operates at Layer 3, SGTs are for macro-segmentation and policy, and Port Security controls MAC address access but does not prevent communication between authorized hosts on the same VLAN.0