In the Junos OS architecture,route preference(often referred to as administrative distance in other vendor platforms) is the primary metric used by the Routing Engine to select the "best" path when multiple protocols provide a route to the same destination. Each routing protocol and route type is assigned a default numeric value; the lower the value, the more preferred the route.
According to Juniper Networks technical documentation, anaggregate routeis assigned a default preference of
130. Aggregate routes are a form of static-like route used to group specific routes into a single, broader prefix to reduce the size of routing tables and limit the scope of routing updates. They are "protocol-independent" because they are not learned from a dynamic neighbor but are manually defined by the administrator.
To understand where130fits in the hierarchy, it is helpful to compare it with other common Junos preferences:
* Directly connected interfaces:0
* Static routes:5
* OSPF Internal:10
* IS-IS Level 1/2:15/18
* Aggregate routes: 130
* OSPF AS External:150
* BGP (Internal and External):170
* Generated routes:150
By setting the aggregate route preference to 130, Junos ensures that specific routes learned via IGPs (like OSPF or IS-IS) are preferred over the aggregate. This is essential because an aggregate route is often used as a
"catch-all" or a discard route when more specific path information is missing. If the aggregate had a lower preference (like 5), it might override dynamic routing information, leading to suboptimal routing or black- holed traffic.

tunnel-end-point name {
ipv4 {
source-address 10.255.1.1;
destination-address 10.255.2.0/25;
}
gre {
key 9;
}
}
The ip and gr interface types are used as endpoints for various tunneling protocols. ip is a generic term that can refer to any IP-based tunnel, while gr specifically refers to Generic Routing Encapsulation (GRE) tunnel interfaces in Junos.

The network is being advertised into OSPFv2 because the LAN-facing interface is enabled under OSPF. It is also being advertised into OSPFv3 for IPv4 because OSPFv3 is configured with the ipv4-unicast realm on the same interface. As a result, R1 learns 172.16.2.0/24 through both protocol instances and will have both protocol entries for that prefix.

To ensure that MPLS traffic-engineered routes are used without affecting IGP routes in the route tables, the mpls-forwarding traffic engineering setting should be used. This setting allows MPLS to influence forwarding without changing the IGP route selection.