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Webcast-Catalyst9k
New Member

uRPF question

How does unicast reverse path forwarding work when there is a default route in the FIB?

uRPF does a reverse check to make sure that the return sourced traffic can make it back through that same interface otherwise its dropped. Now what happens if its a spoofed source IP and uRPF checks the FIB and there is a default route? It still forwards it as usual, or am I confused?

1 REPLY
Cisco Employee

Re: uRPF question

Sparky,

The default route is not considered unless you configure the allow-default keyword as follow:

ip verify unicast source reachable-via any allow-default

Regards

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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