Verifying Next Hops For Static Routes; How Bfd Next-Hop Verification Works - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - IP-IPV6-IGP CONFIGURATION GUIDE 2010-10-31 Configuration Manual

JunosE 11.3.x IP, IPv6, and IGP Configuration Guide

Verifying Next Hops for Static Routes

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Configure a static route to 10.2.0.0/16 with a next hop of 10.5.0.2 (which is not directly
1.
connected) and an administrative distance of 254 (which is worse [higher] than the
default administrative distance for static routes [1]).
host1(config)#ip route 10.2.0.0 255.255.0.0 10.5.0.2 254
Configure another static route that resolves 10.5.0.2 and uses the default administrative
2.
distance.
host1(config)#ip route 10.5.0.0 255.255.255.252 10.1.0.2 [ 1 ]
NOTE: The previous example shows the default administrative distance
value, 1, to illustrate the difference between the two static route
commands. However, you do not have to enter this value when issuing
the command.
A static route to 10.2.0.0 is added to the route table with a next hop of 10.1.0.2 (on the
directly connected Ethernet interface).
NOTE: A dynamically learned route can also resolve indirect next hops,
as long as the administrative distance value of the learned route is better
(lower) than the static route whose next hop is being resolved.
You can configure either Bidirectional Forwarding Detection (BFD) or Response Time
Reporter (RTR) probes to further control when a static route is installed in the routing
table. Using either BFD or RTR, static route installation is based on two factors: whether
the next hop to the specified destination is resolved, and whether an IP service running
above the static route application is currently available.
Next-hop verification is useful for static route configurations in which the layer 2 and
layer 3 interfaces are up and the next hop to the specified destination is available, but
the IP services that run above the static route are currently unavailable. When the
upper-layer IP services are unavailable, the router does not install the static route in its
routing table.

How BFD Next-Hop Verification Works

Static routes on E Series routers can use Bidirectional Forwarding Detection (BFD) to
verify the availability of the next hop and obtain the state of the IP service. For additional
information about BFD, see JunosE IP Services Configuration Guide.
If you specify the bfd-liveness-detection keywords with a minimum receive interval,
minimum transmit interval, or multiplier when you issue the ip route command to establish
a static route, the router verifies the next-hop status and installs the static route in the
routing table under the following conditions:
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