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ZXR10 8900 Series User Manual (Basic Configuration Volume)
IP address may also be used to wage an attack as long as it is
unreachable.
Module 2
Another network model is shown in
Figure 38
.
F
IGURE
38 S
OURCE
A
DDRESS
S
NOOPING
2
The attacker may forge a source address that is the address of
another legal network and exists in global routing table. For ex-
ample, attacker may forge a source address so that the attacked
will think that the attack comes from forged source address but
in fact source address is completely innocent. In addition, some-
times network administrator will close all data flows coming from
that source address and this in return makes DOS attack of the
attacker successfully become true.
A more complex scenario is that TCP SYN flooding attack will cause
TCP SYN-ACK data packet to be sent to many hosts completely
independent of the attack and such hosts will become victims. As
a result, attacker may spoof one or more systems at the same
time.
Similarly, UDP and ICMP may be used to implement flooding at-
tacks.
All these attacks will severely lower the system performance or
even cause system to crash. URPF is a technology to guard against
such attacks.
Configuring URPF
There are three types of URPF: Strict URPF (SRPF), Loose URPF
(lRPF) and URPF that ignores the default route (lnRPF).
To configure URPF, perform the following steps.
Step Command
Function
1
ZXR10(config-if)#
ip verify
{
strict
|
loose
|
loose-ingoring-default-route
}
This enables the URPF check
function on an interface
2
ZXR10(config-if)#
urpf log
{
on
|
off
}
This enables or disables the
URPF log function
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