In BGP, what is required for sending an Update message after an export route policy change?

When a route policy change occurs in BGP (Border Gateway Protocol), a manual operation is necessary to trigger the sending of an Update message. This is because BGP does not automatically propagate route changes immediately after a policy alteration. The protocol is designed this way to allow network administrators to have control over when updates are sent to avoid unnecessary fluctuations in routing tables.

To apply route policy changes effectively, the administrator typically needs to execute specific commands to advertise the updated routes to BGP peers. This ensures that the changes are intentional and that the administrator is ready to manage the impact of the new routing information on the network.

In contrast, automatic updates without manual intervention could lead to unstable routing, as continuous and unsolicited changes might disrupt the equilibrium of the network. Other options, such as rebooting the router or relying on timers, do not align with the operational procedures typical of BGP, which emphasize manual control over route propagation.