HP MSR2000/3000/4000 Router Series Security Configuration Guide

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To enable ACL checking for de-encapsulated packets:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enable ACL checking for
de-encapsulated packets.
ipsec decrypt-check enable By default, this feature is enabled.
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 is
not required, and the de-encapsulation process consumes large amounts of resources and degrades
performance, resulting in DoS. IPsec anti-replay can check and discard replayed packets before
de-encapsulation.
In some cases, some service data packets might be received in a very different order than their original
order, and the IPsec anti-replay function might drop them as replayed packets, affecting normal
communications. If this happens, disable IPsec anti-replay checking or adjust the size of the anti-replay
window as required.
IPsec anti-replay does not affect manually created IPsec SAs. According to the IPsec protocol, only
IKE-based IPsec SAs support anti-replay checking.
IMPORTANT:
• IPsec anti-replay is enabled by default. Be careful when you disable IPsec anti-replay. Failure to detect
anti-replay attacks might result in denial of services.
• Specify an anti-replay window size that is as small as possible to reduce the impact on system
performance.
To configure IPsec anti-replay:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enable IPsec anti-replay.
ipsec anti-replay check
By default, IPsec anti-replay is
enabled.
3. Set the size of the IPsec
anti-replay window.
ipsec anti-replay window width The default size is 64.
Binding a source interface to an IPsec policy
For high availability, a core device is usually connected to an ISP through two links, which operate in
backup or load sharing mode. The two interfaces negotiate with their peers to establish IPsec SAs