260
To do…
Command…
Remarks
3.
Enable the encryption engine
(on a distributed router).
cryptoengine enable
[
slot
slot-
number
]
Optional
Enabled by default
Enabling ACL checking of de-encapsulated IPsec packets
In tunnel mode, the IP packet that was encapsulated in an inbound IPsec packet may not be an object
that is specified by an ACL to be protected. For example, a forged packet is not an object to be
protected. If you enable ACL checking of de-encapsulated IPsec packets, all packets that fail the
checking are discarded, improving the network security.
To enable ACL checking of de-encapsulated IPsec packets:
To do…
Command…
Remarks
1.
Enter system view.
system-view
—
2.
Enable ACL checking of de-
encapsulated IPsec packets.
ipsec decrypt check
Optional
Enabled by default
Configuring the IPsec anti-replay function
The IPsec anti-replay function protects networks against anti-replay attacks by using a sliding window
mechanism called "anti-replay window." This function checks the sequence number of each received
IPsec packet against the current IPsec packet sequence number range of the sliding window. If the
sequence number is not in the current sequence number range, the packet is considered a replayed
packet and is discarded.
IPsec packet de-encapsulation involves complicated calculation. De-encapsulation of replayed packets
not only makes no sense, but also consumes large amounts of resources and degrades performance,
resulting in DoS. IPsec anti-replay checking, when enabled, is performed before the de-encapsulation
process, reducing resource waste.
In some cases, however, the sequence numbers of some normal service data packets may be out of the
current sequence number range, and the IPsec anti-replay function may drop them as well, affecting the
normal communications. If this happens, disable IPsec anti-replay checking or adjust the size of the anti-
replay window as required.
CAUTION:
•
IPsec anti-replay checking is enabled by default. Do not disable it unless it must be disabled.
•
A wider anti-replay window results in higher resource cost and more system performance
degradation, which is against the original intention of the IPsec anti-replay function. Specify an anti-
replay window size that is as small as possible.
To do…
Command…
Remarks
1.
Enter system view.
system-view
—
2.
Enable IPsec anti-replay
checking.
ipsec anti-replay check
Optional
Enabled by default