IPSEC ASA 8.0(2)

johnroche_2 · ‎08-28-2007

Hi

I have an ASA 5520 running an IPSEC tunnel to a 3825.

Everyday the tunnel drops and the following message appears in the logs.

%ASA-1-713900: Group = 10.254.254.45, IP = 10.254.254.45, construct_ipsec_delete(): No SPI to identify Phase 2 SA!

I thought the re-key of the tunnel happens without the tunnel dropping.

Is this a Bug or have I done something stupid.

John

j-block · ‎09-03-2007

This error message means that the ASA received a packet that had no SPI (Security Parameter Index) number to encrypt/decrypt the packet. When an IPSec tunnel is established, it assigns an inbound and outbound SPI number.

In your case, it looks as though the ASA has received an encrypted packet from the said peer and is unable to decrypt it due to no matching SPI. After deletion, the remote side should be able to renegotiate new SPI numbers with the ASA (if necessary). There are bugs on similar issues but they are on version 7.2, so I dont think those will be applicable here. If you are initailly able to start the tunnel then there is no configuration problem. The tunnel will automatically renegotiate any time is some problem occurs.

johnroche_2 · ‎09-03-2007

Hi

I finally got to the bottom of this.

Both the ASA and the router had SA lifetimes of 86400. On the ASA side PFS was on and on the router it was not.

There seemed to be two issues,

1 The tunnel dropped depending on who initated the rekey, the router or the ASA,

2 The SA lifetime gave mixed results.

Solution

enable PFS on router and changed the SA to 2880 on both the router and ASA.