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When you show the received route from a specific neighbor in BGP with a Juniper, the output is the following :

show route receive-protocol bgp X.X.X.X      

inet.0: V destinations, W routes (X active, Y holddown, Z hidden)
[...]

What is the difference beetween "destinations", "routes" and "active", "holddown", "hidden" ?

Which prefixes are put into the GRT and which one are shared in iBGP (full mesh or RR) ?

According to the documentation the "hidden" are the routes that is not used because of a routing policy but this routes are shared in iBGP ?

Edit

Same question for the BGP summary command :

show bgp summary 
Threading mode: BGP I/O
Groups: X Peers: Y Down peers: Z
Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
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First, I think it helps to set the baseline for the general process of how BGP routes are processed, this is true for all vendors.

There are 3 main components:

  • ADJ-RIB-IN: This is the table where all received routes from a specific neighbor are stored prior to policy processing and BGP path selection.
  • LOCAL-RIB: AKA the global routing table. Routes stored here are the result of import policy processing and BGP path selection.
  • ADJ-RIB-OUT: This is the table where all of the best path selected BGP routes destined for a particular neighbor are processed against any export policies and are going to be advertised.

On Junos:

  • show route receive-protocol bgp A.B.C.D looks at ADJ-RIB-IN
  • show route looks at the LOCAL-RIB (i.e. routing table)
  • show route advertising-protocol bgp A.B.C.D looks at ADJ-RIB-OUT

Now that we have that reference, on to your specific questions.

What is the difference beetween "destinations", "routes" and "active", "holddown", "hidden" ?

The line of output you're referring to is the status of the LOCAL-RIB/Routing Table (inet.0).

jhead@R1> show route receive-protocol bgp 192.168.1.1

inet.0: 887870 destinations, 6884733 routes (887867 active, 1 holddown, 3 hidden)

The above example basically says that currently in inet.0 (the global routing table) has X number of routes in each status.

  • Destinations refer to the number of unique destination prefixes.
  • Routes refer to the number of total routes to those prefixes, it factors in multiple routes to the same destination.
  • Active refers to the number of resolved destinations.
  • Holddown refers to the number of routes that are pending (i.e. not yet inactive).
  • Hidden refers to the fact that the route cannot be resolved for some reason. That could be due to policy or because it can't reach the next-hop associated with the route.

What your example doesn't show is actual received routes, so I'll extend to the example from above:

jhead@R1> show route receive-protocol bgp 192.168.1.1 

inet.0: 887869 destinations, 6884721 routes (887866 active, 1 holddown, 3 hidden)
  Prefix          Nexthop          MED     Lclpref    AS path
  1.0.0.0/24              74.40.0.147          0       80         13335 I
                          74.40.0.226          0       80         13335 I
  1.0.4.0/22              74.40.0.60           0       80         6939 4826 38803 I
                          74.40.0.26           0       80         6939 4826 38803 I
  1.0.4.0/24              74.40.0.60           0       80         6939 4826 38803 I
                          74.40.0.26           0       80         6939 4826 38803 I

Which prefixes are put into the GRT and which one are shared in iBGP (full mesh or RR) ?

Remember, this is the ADJ-RIB-IN, so it shows routes prior to policy processing and BGP best path selection. You need to run show route to see what is installed in the routing table.

The show route advertising-protocol bgp A.B.C.D can show you what is advertised to a particular neighbor. The neighbor you run this command for will factor in whether it's IBGP (RR, etc.) or EBGP.

Same question for the BGP summary command :

Here's a partial example that points to the variables you're asking about:

jhead@R1> show bgp summary
Threading mode: BGP I/O
Default eBGP mode: advertise - accept, receive - accept
Groups: 7 Peers: 15 Down peers: 4
<...snip...>
  • Groups refer to the number of BGP groups that are configured (set protocols bgp group ABC ...)
  • Peers refer to the total number of BGP peers on the router, regardless of status.
  • Down peers refer to the number of BGP peers that are down out of total number of peers.

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