Segment routing labels can be distributed by link-state routing protocols such as IS-IS and OSPF, which have been extended to support segment routing capabilities.References:

• Segment Routing Overview, Juniper Networks Documentation
• Understanding Segment Routing with OSPF, Juniper Networks Documentation
• Understanding Segment Routing with IS-IS, Juniper Networks Documentation

The root bridge in a spanning-tree network is the bridge with the smallest or the lowest bridge ID.

In the absence of a manually configured priority, the Spanning Tree Protocol (STP) elects the root bridge based on the lowest bridge ID, which is a combination of the priority and the MAC address. The device with the lowest MAC address will have the lowest bridge ID and thus be elected as the root bridge.

References

• Juniper Networks Technical Documentation on STP

The exhibit shows an aggregate route configuration for the network172.21.0.0/22, which would summarize the specific networks172.21.0.0/24,172.21.1.0/24, and172.21.2.0/24. For an aggregate route to be active, it must have contributing routes in the routing table. If the route is hidden, it usually means there are no contributing routes that are active or the policy applied to the aggregate does not match any of the specific routes.Therefore, the first step in troubleshooting would be to verify that there are indeed active contributing routes for the aggregate to be valid.

References:

• Juniper documentation on routing policies and aggregates: Junos OS Routing Policies, Firewall Filters, and Traffic Policers User Guide