User's Manual

22-45
For applications based on IP address verification, such attacks may allow unauthorized users to access the
system as some authorized ones, or even the administrator. Even if the response messages can’t reach the
attackers, they will also damage the targets.
Figure 22-4 URPF application situation
In the above figure, Router A sends requests to the server Router B by faking messages whose source
address are 2.2.2.1/8 .In response, Router B will send the messages to the real ”2.2.2.1/8”. Such illegal
messages attack both Router B and Router C. The application of URPF technology in the situation described
above can avoid the attacks based on the Source Address Spoofing.
22.4.2 URPF Configuration Task Sequence
1. Enable URPF
2. Display and debug URPF relevant information
1. Globally enable URPF
Command
Explanation
Global mode
urpf enable
no urpf enable
Globally enable and disable URPF.
2. Display and debug URPF relevant information
Command
Explanation
Admin and Config Mode
show urpf
Display which interfaces have been
enabled with URPF function.
Router A Router B Router C
1.1.1.8/8 2.2.2.1/8
Source IP：2.2.2.1/8