R2511-HP MSR Router Series Security Configuration Guide(V5)

211
Ste
p
Command Remarks
2. Set the ISAKMP SA keepalive
interval.
ike sa keepalive-timer interval
seconds
No keepalive packet is sent by
default.
3. Set the ISAKMP SA keepalive
timeout.
ike sa keepalive-timer timeout
seconds
No keepalive packet is sent by
default.
Setting the NAT keepalive timer
If IPsec traffic needs to pass through NAT security gateways, you must configure the NAT traversal
function. If no packet travels across an IPsec tunnel in a certain period of time, the NAT mapping might
get aged and be deleted, disabling the tunnel beyond the NAT gateway from transmitting data to the
intended end. To prevent NAT mappings from being aged, an ISAKMP SA behind the NAT security
gateway sends NAT keepalive packets to its peer at a certain interval to keep the NAT session alive.
To set the NAT keepalive timer:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Set the NAT keepalive
interval.
ike sa nat-keepalive-timer interval
seconds
20 seconds by default.
Configuring a DPD detector
DPD irregularly detects dead IKE peers. It works as follows:
1. When the local end sends an IPsec packet, it checks the time the last IPsec packet was received
from the peer.
2. If the time interval exceeds the DPD interval, it sends a DPD hello to the peer.
3. If the local end receives no DPD acknowledgement within the DPD packet retransmission interval,
it retransmits the DPD hello.
4. If the local end still receives no DPD acknowledgement after having made the maximum number of
retransmission attempts (two by default), it considers the peer already dead, and clears the IKE SA
and the IPsec SAs based on the IKE SA.
DPD enables an IKE entity to check the liveliness of its peer only when necessary. It generates less traffic
than the keepalive mechanism, which exchanges messages periodically.
To configure a DPD detector:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Create a DPD detector and
enter its view.
ike dpd dpd-name N/A
3. Set the DPD interval.
interval-time interval-time
Optional.
10 seconds by default.