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

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For the negotiation in phase 2, verify that the parameters of the IPsec policies applied on the interfaces
are matched, and that the referred IPsec transform sets have a match in protocol, encryption and
authentication algorithms.
Failed to establish an IPsec tunnel
Symptom
The expected IPsec tunnel cannot be established.
Analysis
Sometimes this might happen if an IPsec tunnel cannot be established or there is no way to communicate
in the presence of an IPsec tunnel in an unstable network.
If ACLs of both parties are configured correctly, and proposals are also matched, the problem is usually
caused by the reboot of one router after the IPsec tunnel is established.
Solution
• Use the display ike sa command to verify that both parties have established an SA in phase 1.
• Use the display ipsec sa policy command to verify that the IPsec policy on the interface has
established IPsec SA.
• If the two commands show that one party has an SA but the other does not, use the reset ipsec sa
command to clear the IPsec SA that has no corresponding SA, use the reset ike sa command to
clear the IKE SA that has no corresponding IKE SA, and trigger SA re-negotiation.
ACL configuration error
Symptom
ACL configuration error results in data flow blockage.
Analysis
When multiple devices create different IPsec tunnels early or late, a device might have multiple peers. If
the device is not configured with ACL rule, the peers send packets to it to set up different IPsec tunnels in
different protection granularity respectively. As the priorities of IPsec tunnels are determined by the order
they are established, a device cannot interoperate with other peers in fine granularity when its outbound
packets are first matched with an IPsec tunnel in coarse granularity.
Solution
When a device has multiple peers, configure ACLs on the device to distinguish different data flows and
try to avoid configuring overlapping ACL rules for different peers. If it is unavoidable, the subrules in fine
granularity should be configured with higher preferences.