Configuring Peer Address in Expressway-C for Static NAT Mode

D.

Sure, I'd be happy to help explain this in detail!

First, let's start by understanding the context of this question. The Cisco Expressway is a key component of Cisco's collaboration architecture, providing secure access for remote workers and business partners to Cisco Unified Communications Manager (UCM) and other collaboration services. The Expressway-C is typically deployed within the enterprise network, while the Expressway-E is deployed in the DMZ or external network to provide secure access from outside the enterprise.

In this scenario, the engineer wants to configure a zone on the Expressway-E to receive communications from the Expressway-C, in order to allow inbound and outbound calls. When the Expressway-E has only one NIC enabled and is using static NAT mode, the peer address on the Expressway-C needs to be configured correctly in order for communications to flow properly.

Now let's look at the answer choices and evaluate them in the context of the scenario:

A. Expressway-E DHCP: This is unlikely to be the correct answer, as DHCP would typically be used to automatically assign IP addresses to network devices, rather than configuring a specific peer address.

B. Cisco UCM FQDN: This is also unlikely to be the correct answer, as the UCM FQDN (fully qualified domain name) would be used to identify the UCM server, rather than the Expressway-E.

C. Cisco UCM DHCP: Similar to choice A, this is unlikely to be the correct answer, as DHCP would typically be used to automatically assign IP addresses to network devices, rather than configuring a specific peer address.

D. Expressway-E FQDN: This is the most likely correct answer. When the Expressway-E has only one NIC enabled and is using static NAT mode, the peer address on the Expressway-C should be configured using the Expressway-E FQDN, which would typically be a publicly-resolvable domain name that points to the Expressway-E's external IP address. This allows the Expressway-C to establish a secure connection to the Expressway-E over the internet, using TLS and other security protocols.

In summary, the correct answer is likely to be D. Expressway-E FQDN, as this is the most appropriate way to configure the peer address on the Expressway-C in this scenario.