This blog was originally started to better help me understand the technologies in the CCIE R&S blueprint; after completing the R&S track I have decided to transition the blog into a technology blog.

CCIE #29033

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Thursday, April 22, 2010

Question 12

What is RPF?

1 comments:

Packets Analyzed said...

RPF - Reverse Path Forwarding has 3 modes strict mode, loose mode, and VRF mode. RPF can prevent packets that have been spoofed limiting the amount of malicious traffic that may enter the network

Strict Mode: a source IP address that is received on an interface actually has a route out the same interface to the source network that the packet was received. If it is not valid the packet is discarded.

Loose Mode: a source IP address received must have a route in the routing table. If it is not valid the packet is discarded.

VRF Mode: a source IP address received must have a route in the virtual routing table. If it is not valid the packet is discarded.

Multicast also uses RPF to ensure that packets received are legitimate. This reduces the chance of multicast packets being flooded out interfaces that do not require the data.

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