Enabling Acl Checking Of De-Encapsulated Ipsec Packets; Configuring The Ipsec Anti-Replay Function - HP 10500 Series Configuration Manual

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 failing the checking will be
discarded, improving the network security.
To enable ACL checking of de-encapsulated IPsec packets:
Step
1. Enter system view.
2. Enable ACL checking of
de-encapsulated IPsec
packets.

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.
IMPORTANT:
• IPsec anti-replay checking is enabled by default. Do not disable it unless it needs to 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.
IPsec anti-replay checking does not affect manually created IPsec SAs. According to the IPsec protocol,
only IPsec SAs negotiated by IKE support anti-replay checking.
To configure IPsec anti-replay checking:
Step
1. Enter system view.
2. Enable IPsec anti-replay
checking.
Command
system-view
ipsec decrypt check
Command
system-view
ipsec anti-replay check
310
Remarks
N/A
Optional.
Enabled by default.
Remarks
N/A
Optional.
Enabled by default.