Figure 12: Sample Configuration For Next-Hop Verification; Table 6: Next-Hop Verification Results For Sample Configuration - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - IP-IPV6-IGP CONFIGURATION GUIDE 2010-10-31 Configuration Manual

Copyright © 2010, Juniper Networks, Inc.
system and an E Series router: Fast Ethernet interface 4/0 and Fast Ethernet interface
4/1. At any given time, only one of these interfaces forwards IP traffic, even though the
associated layer 2 interfaces may be up concurrently.
On the E Series router, Fast Ethernet interfaces 4/0 and 4/1 are configured as unnumbered
IP interfaces. In addition, each interface has an RTR probe configured as an echo type
that sends requests over the interface to determine its availability. RTR 10 sends requests
over Fast Ethernet interface 4/0, and RTR 11 sends requests over Fast Ethernet interface
4/1.
In this example, both RTR 10 and RTR 11 use the IP address of the remote system (10.1.1.2)
as the target address. When you configure multiple RTR entries to use the same target
address, you must set the receive-interface attribute to specify the interface on which
the probe expects to receive responses. (See Step 4c in the next section, "Configuring
RTR Next-Hop Verification" on page 34.) This action enables the router to map incoming
responses to the proper RTR entry, even when multiple RTR entries have the same target
address.

Figure 12: Sample Configuration for Next-Hop Verification

The ip route command is issued for each interface with the verify rtr and last-resort
keywords to establish the necessary static routes. (See Steps 6 and 7 in the next section,
"Configuring RTR Next-Hop Verification" on page 34.) This command causes the results
described in Table 6 on page 33, based on the status of the associated RTR operations.

Table 6: Next-Hop Verification Results for Sample Configuration

RTR 10 Status RTR 11 Status
Up Up
Up Down
Down Up
Results
The router installs an equal-cost multipath (ECMP)
route to 10.1.1.2 in the routing table, using Fast Ethernet
interfaces 4/0 and 4/1 as the next hops.
The router installs a route to 10.1.1.2, using
Fast Ethernet interface 4/0 as the next hop.
The router installs a route to 10.1.1.2, using
Fast Ethernet interface 4/1 as the next hop.
Chapter 1: Configuring IP
33