Enabling Invalid Spi Recovery; Setting The Limit On The Number Of Ike Sas - HP 6125XLG Configuration Manual

4. If the local device receives no response after two retries, the device considers the peer is dead, and
deletes the IKE SA along with the IPsec SAs it negotiated.
5. If the local device receives a response from the peer during the detection process, the peer is
considered alive. The local device performs a DPD detection again when the triggering interval is
reached or it has traffic to send, depending on the DPD mode.
Follow these guidelines when you configure the IKE DPD function:
• When DPD settings are configured in both IKE profile view and system view, the DPD settings in IKE
profile view apply. If DPD is not configured in IKE profile view, the DPD settings in system view apply.
It is a good practice to set the triggering interval longer than the retry interval so that a DPD
•
detection is not triggered during a DPD retry.
To configure IKE DPD:
Step
1. Enter system view.
2. Enable sending IKE DPD
messages.

Enabling invalid SPI recovery

An IPsec "black hole" occurs when one IPsec peer fails (for example, a peer can fail if a reboot occurs).
One peer fails and loses its SAs with the other peer. When an IPsec peer receives a data packet for
which it cannot find an SA, an invalid SPI is encountered. The peer drops the data packet and tries to
send an SPI invalid notification to the data originator. This notification is sent by using the IKE SA.
Because no IKE SA is available, the notification is not sent. The originating peer continues sending the
data by using the IPsec SA that has the invalid SPI, and the receiving peer keeps dropping the traffic.
The invalid SPI recovery feature enables the receiving peer to set up an IKE SA with the originator so that
an SPI invalid notification can be sent. Upon receiving the notification, the originating peer deletes the
IPsec SA that has the invalid SPI. If the originator has data to send, new SAs will be set up.
Use caution when enabling the invalid SPI recovery feature because using this feature can result in a DoS
attack. Attackers can fabric a great number of invalid SPI notifications to the same peer.
To enable invalid SPI recovery:
Step
1. Enter system view.
2. Enable invalid SPI recovery.

Setting the limit on the number of IKE SAs

You can set the maximum number of half-open IKE SAs and the maximum number of established IKE SAs.
Command
system-view
ike dpd interval interval-seconds
[ retry seconds ] { on-demand |
periodic }
Command
system-view
ike invalid-spi-recovery enable
231
Remarks
N/A
By default, IKE DPD is disabled.
Remarks
N/A
By default, the invalid SPI recovery
is disabled.