Exam 300-620 topic 1 question 29 discussion

C is the right answer. For the Leaf connected to L3out, Source MAC is learnt only while other leafs do not learn source MAC or IP when they receive traffic from L3out.

Correct answer is C. ACI uses concept like traditional networking for L3 out connectivity. IT uses RIB and ARP table,not local endpoint table. IT doesn't learn IP address from data plane; it learns the subnet via control plane using routing protocol It learns MAC address of next-hop(router) for this subnet from data plane. As the mac address is the MAC of the router (not that of the endpoint) and it doesn't learn endpoint IP address(/32 or /128), leaf doesn't learn MAC or IP of the endpoint when it receives from L3out

C is right answer. Local endpoint learning with an incoming packet from L3Out to Cisco ACI: Only the source MAC address is learned as a local endpoint. The source IP address is not learned as a local endpoint. Remote endpoint learning with an incoming packet from L3Out to Cisco ACI: No source MAC or IP address is learned as a new remote endpoint by a packet.*

C is correct. L3Out is a way to communicate ACI infrastructure using endpoint learning with the traditional network which uses flood, arp, mac, IP and all of them as DESTINATION and not SOURCE as ACI.

No source MAC or IP address is learned as a new remote endpoint by a packet.* https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html#Silenthostsconsiderations

C is correct. Only source MAC is learned.

Routing Over Learning: For traffic from L3Outs like the Internet, ACI relies more on routing protocols and policy-based forwarding rather than endpoint learning. The fabric will use its routing table to forward traffic to the appropriate destinations, based on the routes learned through dynamic routing protocols or static routing configurations.

Cisco ACI uses a behavior similar to that in traditional networks for L3Out connectivity. The Cisco ACI L3Out domain learns the MAC address only from the data plane. IP addresses are not learned from the data plane in an L3Out domain; instead, Cisco ACI uses ARP to resolve next-hop IP and MAC relationships to reach the prefixes behind external routers.

assume local EP Local endpoint learning with an incoming packet from L3Out to Cisco ACI: Only the source MAC address is learned as a local endpoint. The source IP address is not learned as a local endpoint. Remote endpoint learning with an incoming packet from L3Out to Cisco ACI: No source MAC or IP address is learned as a new remote endpoint by a packet https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html#L3Outendpointlearningconsiderations see figure 7 wich explain it very well

C is my vote - based on snip [The Cisco ACI L3Out domain learns the MAC address only from the data plane. IP addresses are not learned from the data plane in an L3Out domain; instead, Cisco ACI uses ARP to resolve next-hop IP and MAC relationships to reach the prefixes behind external routers.] https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

B is the right answer. For C, without source mac and IP, how the return traffic will flow?

In this document https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html#L3Outendpointlearningconsiderations it is made clear that no remote endpoint is learned by the egress leaf (Leaf 1 in figure 7). The stale endpoint issue is actually due to this fact.

B is definitely not correct. As per Cisco White paper- Cisco ACI learns a MAC or IP address as a remote endpoint when a packet comes into a Cisco ACI leaf switch from another leaf switch through a spine switch. So remote endpoints are those which are connected to other leaf. I think correct answer is A.

B is the right answer. The Cisco ACI L3Out domain learns the MAC address only from the data plane. IP addresses are not learned from the data plane in an L3Out domain; instead, Cisco ACI uses ARP to resolve next-hop IP and MAC relationships to reach the prefixes behind external routers. https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

I think D is right. The question say on Egress switch... Egress is LEAF 2 in fig5. "In figure 5........ only IP address 192.168.1.1 is learned as a remote endpoint on LEAF2." https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

ocal endpoint learning with an incoming packet from L3Out to Cisco ACI: C, Only the source MAC address is learned as a local endpoint. The source IP address is not learned as a local endpoint.