By default, for a FortiGate to advertise a prefix specified by the BGP network command, an identical prefix (network and subnet mask) must exist in its routing table. The exhibit shows FGT-B is configured to advertise 172.16.0.0/16, but its routing table only contains the more specific, directly connected route 172.16.54.0/24. Due to this mismatch, the route is not advertised.

To fix this, the administrator can either:

A. Change the network command to 172.16.54.0/24 for an exact match.

D. Disable the default behavior by using the command set network-import-check disable, which allows BGP to advertise prefixes from the network list even without an exact match in the routing table.

B. Manually adding a route on the receiving router (FGT-A) does not fix the advertisement problem on the sending router (FGT-B) and defeats the purpose of dynamic routing.

C. A BGP reset only forces peers to re-exchange their existing routing information. It will not fix the underlying configuration issue that prevents FGT-B from advertising the route.

1. FortiOS Administration Guide 7.6, Networking > BGP, Section: "Advertising networks". The guide explains that the network command is used to advertise networks and implies the need for the route to exist in the routing table.

2. FortiOS CLI Reference 7.6, router > bgp. The documentation for set network-import-check {enable | disable} specifies its function: "Enable/disable checking for presence of network in routing table." The default is enable. Disabling this check is a valid solution to the described problem.