Referring to the exhibit, you have a data center in which only the spine devices are using EVPN and VXLAN. The leaf nodes are multihomed in active-active mode to the spine nodes through ESI LAG interfaces. In this design, a link failure on the interface connecting the spine nodes would also cause all traffic from the spine to the leaf nodes to drop.
In this scenario, which command configured on which nodes would solve this problem?
In this scenario, the core isolation feature causes the traffic from the spine to the leaf nodes to drop when the link between the spine nodes fails. To avoid this, you need to disable core isolation on the spine nodes. The command to disable core isolation is 'set protocols evpn no-core-isolation', and it should be configured on the spine nodes. This command allows traffic to continue flowing between the spines and the leaf nodes even if there is a link failure between the spine nodes.
A is correct answer. In cases like this, you can set "no-core-isolation" at the [edit protocols evpn] configuration hierarchy level on each spine device to disable the core isolation feature https://www.juniper.net/documentation/us/en/software/junos/evpn-vxlan/topics/concept/evpn-vxlan-core-isolation-disabling.html
Carefully reading question: "a link failure on the interface connecting the spine nodes would also cause all traffic from the spine to the leaf nodes to drop" (look to the picture, all links are failed) If link between spines fails and all traffic are dropped, then Core-Isolation feature is already deployed, then we need to Disable it. Correct C.
C is the correct answer https://www.juniper.net/documentation/us/en/software/junos/evpn-vxlan/topics/concept/evpn-vxlan-core-isolation-disabling.html
My God. How can u say C). is A