What is the default value of the link-state advertisement (LSA) refresh timer in the Junos OS?

The default value of the link-state advertisement (LSA) refresh timer in the Junos OS is 30 minutes. This timer is crucial for OSPF (Open Shortest Path First) protocol operation because it dictates how frequently OSPF routers must refresh their link-state advertisements to ensure that all routers have up-to-date topology information.

In OSPF, routers exchange link-state information to build a consistent view of the network. The refresh timer ensures that stale information is not kept in the OSPF database longer than necessary. A longer timer might result in outdated topology information, affecting routing decisions and potentially leading to suboptimal routing paths.

Setting the default refresh timer to 30 minutes strikes a balance between network traffic and timely updates of the topology. This helps maintain efficient routing without overwhelming the network with too frequent updates. The other options do not reflect the standard configuration of OSPF in Junos OS, which is why they are not the correct choice.