How to Summarize Junos Routing Information

Sometimes you may just want a quick summary of the routing information on your router. As an example, you have just configured OSPF in your network, and you’re expecting to see a certain number of OSPF routes in your routing table. You can issue a show route summary command to see that all the routes are there.

user@router1> show route summary
 
Autonomous system number: 69
Router ID: 10.255.71.52
 
inet.0: 24 destinations, 25 routes (23 active, 0 holddown, 1 hidden)
Restart Complete
       Direct:   6 routes,   5 active
        Local:   4 routes,   4 active
        OSPF:   5 routes,   4 active
       Static:   7 routes,   7 active
        IGMP:   1 routes,   1 active
         PIM:   2 routes,   2 active
 
inet.3: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
Restart Complete
        RSVP:   2 routes,   2 active
 
iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
Restart Complete
       Direct:   1 routes,   1 active
 
mpls.0: 7 destinations, 7 routes (5 active, 0 holddown, 2 hidden)
Restart Complete
        MPLS:   3 routes,   3 active
        VPLS:   4 routes,   2 active
 
inet6.0: 5 destinations, 5 routes (5 active, 0 holddown, 0 hidden)
Restart Complete
       Direct:   2 routes,   2 active
         PIM:   2 routes,   2 active
         MLD:   1 routes,   1 active

The route summary includes several key pieces of information:

  • Autonomous system number: The AS number configured for your router (if any exists) is displayed here. This number really just reflects and validates your AS number configuration.

  • Router ID: If you’ve configured a Router ID, it shows up here. If you haven’t, the router uses the lo0 address (the first non-127.0.0.1 address) as the router ID.

  • Routing table name: Each stanza in the output corresponds to a different routing table within the router. You’ll generally be looking in the base table, which is the inet.0 table in this example. If you’ve configured MPLS, you’ll see routes in the inet.3 and mpls.0 tables. The inet.6 table is reserved for IPv6.

  • Routes: Each routing table has a summary of the total number of routes in the table. In this case, they’re categorized as follows:

    • active: Routes that are active, meaning they are being used in the forwarding table.

    • holddown: These routes are in holddown state, which basically means that they’re in the process of becoming inactive. This state is rarely seen as it’s a transitional state between active and inactive status.

    • hidden: These routes exist on the router, but aren’t being used for forwarding packets because of some routing policy in use. For example, you may be using a filter of some sort to select one route over another. The route that would have been selected is a hidden route. The route that is selected for forwarding must be an active route.

A major reason that otherwise functional routes are no longer being used in the forwarding table is that they have somehow become hidden!

When you’re looking for a particular route or a set of routes, it can be quite painful to have to go through 50 pages of routing information. You don’t want your route to be the proverbial needle in a haystack. You need a way to search for a particular route. To find a specific route, use the exact modifier:

user@router1> show route exact 207.17.136.0/24
 
inet.0: 24 destinations, 25 routes (23 active, 0 holddown, 1 hidden)
Restart Complete
+ = Active Route, - = Last Active, * = Both
207.17.136.0/24  *[Static/5] 2d 03:30:22
          > to 192.168.71.254 via fxp0.0

This command pretty much limits the output to only the requested route. You can use it with the various detail modifiers (terse, brief, detail, or extensive).

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