Which statement is true?

A host EPG Client wants to talk to a webserver in EGP Web. A contract with default settings is defined between EPG Client and EPG Web, which allows TCP communication initiated by the client toward the webserver with TCP destination port 80.

Which statement is true?
A . If EPG Web is made a preferred group member, a contract between EPG Client and EPG Web is no longer required for the host in EPG Client to reach the webserver in EPG Web.
B. If vzAny is configured to consume and provide a "deny all" contract, traffic between EPG Client and EPG Web is no longer allowed.
C. The host in EPG Client is allowed to connect to TCP destination port 80 on the webserver in EPG Web.
The webserver will not be allowed to initiate a separate TCP connection to a host port with TCP source port 80.
D. The host in EPG Client is allowed to connect to TCP destination port 80 on the webserver in EPG Web.
The webserver is allowed to initiate a separate TCP connection to a host port with TCP source port 80.

View Answer

Answer: D

Explanation:

Apply Both Direction and Reverse Filter Port in the subject for the filter. These two options are by default enabled…This means that if the provider EPG initiates traffic toward the consumer EPG, the Cisco ACI fabric allows it for any destination ports if the source port is 80.

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/1-x/Operating_ACI/guide/b_Cisco_Operating_ACI/b_Cisco_Operating_ACI_chapter_01000.html

Reverse filter and apply in both directions is default.

If a filter allows traffic from any consumer port to a provider port (e.g. 8888), if reverse port filtering is enabled and the contract is applied both directions (say for TCP traffic), either the consumer or the provider can initiate communication. The provider could open up a TCP socket to the consumer using port 8888, whether the provider or consumer sent traffic first.

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/1-x/Operating_ACI/guide/b_Cisco_Operating_ACI/b_Cisco_Operating_ACI_chapter_01000.html