[strongSwan-dev] 2 transport mode CHILD SAs, tunnel up, connection down

James Hulka jah at open.ch
Mon Mar 25 09:23:27 CET 2013

Hello Martin,

Thank you for your reply. Just for clarification the current
configuration I am testing is using IKEv1.

I tested again using reauth=no and after 4 days I once again had a
single tunnel disappear for 44 minutes which would be in the right range
for rekeying (keylife=1h, rekeymargin=9m).

To further clarify the configuration it may be helpful to know that I am
building 4 tunnels between 2 interfaces on one host to 2 interfaces on
another host:

h1 eth0 <--> h2 eth0
h1 eth0 <--> h2 eth1
h1 eth1 <--> h2 eth0
h1 eth1 <--> h2 eth1

Any thoughts/ideas would be much appreciated.



On 03/18/2013 03:22 PM, Martin Willi wrote:
> Hi James,
>> It should be noted that I had tested the same setup with the
>> configuration option 'reauth=no' previously for 5 days without such a
>> situation appearing. I then removed this option and after 2 days of
>> testing I had the problem described above.
> It is hard to say what ultimately lead to the second CHILD_SA, but that
> reauthentication is involved is certainly possible.
> Reauthentication is actually a kludge in IKEv2, as it just reestablished
> the IKE and all CHILD_SAs from scratch. There are situations that are
> hard to handle, for example if one peer re-authenticates while to other
> rekeys a CHILD_SA. Another problem arises if, for example, a trap policy
> (auto=route) triggers while the remote end has closed the IKE_SA just
> before recreating it during re-authentication.
> I usually recommend to set reauth=no, as it is just not required for
> most setups to re-evaluate credentials. If it is in your setup, you
> might consider having rekey/reauth times that always the same peer
> initiates the reauthentication/rekeying. This certainly can help in
> avoiding the issue you have seen.
> Regards
> Martin

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