Is it only one Active route for a special destination?

Question

When I read juniper document about show route:

I show route IP:

admin@MX480> show route 14.104.112.1

inet.0: 837234 destinations, 1784889 routes (832157 active, 0 holddown, 862249 hidden)
+ = Active Route, - = Last Active, * = Both

14.104.112.0/21   *[BGP/170] 6w4d 23:44:08, localpref 132
                      AS path: 58931 I, validation-state: unverified
                    > to 12.19.8.10 via gr-3/1/10.8
                    [BGP/170] 2w6d 10:12:47, MED 10, localpref 110
                      AS path: 3257 174 I, validation-state: unverified
                    > to 6.74.41.129 via ae5.0
                    [BGP/170] 1w3d 11:23:37, localpref 105
                      AS path: 4809 4134 I, validation-state: unverified
                    > to 208.30.49.165 via ae2.0

I have several questions:

1.what's the destinations meaning ? in document it say Number of destinations for which there are routes in the routing table. you see in routing table there have 14.104.112.0/21 in it, the destinations number is 2048 or 1?

2.you see the 1784889 routes (832157 active, 0 holddown, 862249 hidden), why 1784889 != 832157 + 0 + 862249?

3.what's the Last Active meaning? is it mean to a destination, the last route usage is it, right? why the example 14.104.112.0/21 there have 3 routes, but only one active? why the other two do not active? is it only one route for a special destination by default?

Answer 1

1. destinations is the number of known subnets in the table, e.g. 192.0.2.0/24 or 14.104.112.0/21. routes is the number of routes to these destinations.
2. There's only one active route to each destination. Those routes that are not used are hidden from the effective routing table (or spare).
3. Last Active is the route that was last chosen for a specific destination. When there are multiple routes to a destination, one is chosen (Active) based on localpref (higher is better).

In the page you've linked, there are more detailed explanations linked below List of Sample Output.