Pass the Cisco CCNP Data Center 300-620 Questions and answers with ValidTests

The feature that dynamically assigns or modifies the EPG association of virtual machines based on their attributes is uSeg EPGs. uSeg EPGs allow for microsegmentation within the Cisco ACI environment, enabling the dynamic assignment of VMs to EPGs based on attributes such as VM name, tag, or other identifiers

 A bridge domain in Cisco ACI represents a Layer 2 forwarding construct345. It defines a unique Layer 2 MAC address space and can include one or more subnets. Bridge domains are associated with a VRF and can contain multiple EPGs345.

With unicast routing enabled on the bridge domain, the two conditions that enable the Cisco ACI leaf to learn a source IP as a local endpoint are:

Through Ethernet traffic received in a bridge domain (Option A): The leaf switch learns the source IP address as a local endpoint when it receives Ethernet traffic within the bridge domain.

Through ARP received on an SVI (Option E): The leaf switch also learns the source IP address as a local endpoint when it receives an ARP request or reply on a Switched Virtual Interface (SVI) associated with the bridge domain.

These conditions allow the ACI fabric to maintain an accurate endpoint database for efficient routing and forwarding of traffic within the fabric.

https://www.cisco .com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

The scenario involves deploying a WAN with Cisco ACI, where Routers 1 and 2 (connected via an L3Out with OSPF Area 0) must receive specific routes (192.168.11.0/24 and 192.168.21.0/24) from the ACI fabric, and reachability to WAN users must be permitted only for servers in vrf_prod. The diagram shows three bridge domains (bd_vlan11, bd_vlan21, bd_vlan31) with their respective subnets and EPGs, all under vrf_prod, along with an L3Out (epg_l3out) for WAN connectivity.

Requirement Analysis

Routers 1 and 2 must receive only routes 192.168.11.0/24 and 192.168.21.0/24:

These subnets belong to bd_vlan11 and bd_vlan21, respectively. To advertise these routes to Routers 1 and 2 via the L3Out, they must be marked with the appropriate scope in the bridge domain configuration.

In ACI, the "Advertised Externally" scope on a subnet ensures that it is advertised to external routers via the L3Out routing protocol (OSPF in this case).

Reachability to WAN users must be permitted only for servers in vrf_prod:

This implies that only the subnets in vrf_prod (192.168.11.0/24, 192.168.21.0/24, and 192.168.31.0/24) should be accessible, but WAN users should only reach specific subnets based on policy.

The external EPG (epg_l3out) represents the WAN users (10.171.0.0/16), and its subnet scope must control inbound reachability.

The subnet 192.168.31.0/24 (bd_vlan31) should not be advertised to the WAN, as it is not listed in the routes Routers 1 and 2 should receive.

Option Evaluation

A. Configure the subnets 192.168.11.0/24 and 192.168.21.0/24 as Private to VRF. Configure the subnet 192.168.31.0/24 as Advertised Externally. Configure an EPG subnet 0.0.0.0/0 as External Subnets for External EPG:

Setting 192.168.11.0/24 and 192.168.21.0/24 as "Private to VRF" means they are not advertised externally, which fails the requirement for Routers 1 and 2 to receive these routes.

Setting 192.168.31.0/24 as "Advertised Externally" incorrectly advertises this subnet to the WAN, which is not desired.

The "External Subnets for External EPG" scope on 0.0.0.0/0 allows WAN users to reach all subnets in vrf_prod, which is correct for reachability.

Conclusion: Fails the first requirement (route advertisement).

When configuring Cisco ACI VMM domain integration with VMware vCenter, the object that is created in vCenter is a VMware vSphere Distributed Switch (VDS)12. The VDS is a virtual switch that extends across all esxi hosts in the cluster and provides a centralized interface from which network configurations can be managed12. This switch allows network administrators to manage networking for multiple hosts and virtual machines from a single interface within vCenter12.

 Changing the Layer 2 unknown unicast policy from Flood to Hardware Proxy results in the traffic being forwarded to one of the spines to perform as a spine proxy4. If the spine proxy also does not know the address, the packet is discarded4.

Enabling the “disable Remote EP learn” feature in Cisco ACI has the effect of preventing border leaf switches from receiving routes through peering with external routers. This feature is particularly useful when there is a mix of Gen1 and Gen2 hardware in the fabric, as it clears all the remote endpoints from the border leaf only. Traffic will still use hardware proxy if the endpoint is not learned on the border leaf, ensuring no operational impact12.

References :=

ACI Fabric Endpoint Learning White Paper2

Cisco Community Discussion on Disable Remote EP Learn

https://unofficialaciguide.com/2018/11/29/aci-best-practice-configurations/

To ensure that destination updates from a newly created L3Out are propagated to all Cisco ACI leaf switches, a BGP route reflector policy should be applied. This policy allows the border leaf switches, which act as BGP route reflectors, to redistribute the learned routes to other leaf switches within the fabric1.