Refer to the exhibit, which shows an enterprise network connected to an internet service provider.

When configuring a loopback interface as the BGP source for connecting to an ISP, two important settings must be applied:

1. Enable EBGP Multihop (ebgp-enforce-multihop)

BGP normally expects directly connected neighbors, but since the ISP and FortiGate A are using loopback interfaces, packets will not be sent directly between their physical interfaces.

The ebgp-enforce-multihop command allows BGP to form an eBGP peering over multiple hops.

2. Set the Update Source (update-source)

Since FortiGate is using a loopback interface as the source, the update-source command ensures that BGP updates originate from the loopback interface rather than a physical interface.

This is essential because BGP peers must match the source IP with the configured neighbor address.