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JUNOS routing table. The output in this recipe shows sections for each type of<br />

routing table. You can also look at just the forwarding table for one of the routing<br />

families:<br />

aviva@RouterA> show route forwarding-table family ?<br />

Possible completions:<br />

inet<br />

IP version 4 (IPv4)<br />

inet6<br />

IP version 6 (IPv6)<br />

iso<br />

International Standards Organization protocol<br />

mpls<br />

Multiprotocol Label Switching<br />

tnp<br />

Trivial Network Protocol<br />

unix<br />

UNIX<br />

The Destination column in each section lists network-layer addresses on which the<br />

router is forwarding traffic, and the last column, Netif, shows the interfaces that are<br />

being used to send traffic toward those addresses.<br />

The Next hop column lists the next hop to the destination. If you compare the inet<br />

routing-table entries in the forwarding table to the entries in the routing table (see<br />

Recipe 8.1), which has routes to the interface addresses 10.0.16.0/24, 10.0.16.1/32,<br />

10.0.21.0/24, and 10.0.21.1/32, and to the router (loopback) address 192.168.42.1/<br />

32, the forwarding table contains entries to reach all these destinations.<br />

The first Type column immediately gives an indication of how the route was placed<br />

into the routing table. perm are permanent routes installed by the JUNOS kernel<br />

when the routing table is initialized, intf are routes learned when an interface was<br />

configured, and dest are remote addresses that are directly connected to an interface.<br />

When a routing protocol is running on the router, you also see the type ucst.<br />

Here, you see a route learned by IS-IS:<br />

aviva@RouterA> show route 10.0.1.0/24<br />

inet.0: 9 destinations, 9 routes (9 active, 0 holddown, 0 hidden)<br />

+ = Active Route, - = Last Active, * = Both<br />

10.0.1.0/24 *[IS-IS/15] 00:11:07, metric 20<br />

> to 10.0.16.2 via fe-0/0/0.0<br />

aviva@RouterA> show route forwarding-table destination 10.0.1.0/24<br />

Routing table: inet<br />

Internet:<br />

Destination Type RtRef Next hop Type Index NhRef Netif<br />

10.0.1.0/24 user 0 10.0.16.2 ucst 337 5 fe-0/0/0.0<br />

A route that is unreachable is marked iddn if the interface to that destination is<br />

down.<br />

The Next hop column is the address used to reach the next hop toward the destination,<br />

and the second Type column gives more information about the next hop. The<br />

last column shows the router’s interface that will be used to send traffic toward the<br />

destination.<br />

262 | Chapter 8: IP Routing<br />

This is the Title of the Book, eMatter Edition<br />

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.

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