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1. Could not find acceptable proposal / no proposal chosen

This is the most common IPsec related error message. It means that depending on which side
initiates tunnel setup, the negotiations in either the IKE or the IPSec phase of setup failed since they
were unable to find a matching proposal that both sides could agree on.

Troubleshooting this error message can be involved since the reasons for this message can be
multiple depending on where in the negotiation it occurred.

•

If the negotiation fails during phase-1 – IKE

The IKE proposal list does not match. Double check that the IKE proposal list matches that of
the remote side. A good idea is to use the ikesnoop verbose CLI command and get the tunnel to
initiate the tunnel from the remote side. It can then be seen what proposals the remote side is
sending and then compare the results with the local IKE proposal list. At least ONE proposal has
to match in order for it to pass phase-1. Remember that the lifetimes are also important, as will
be mentioned in Problem symptom-1.

•

If the negotiation fails during phase-2 – IPsec

The IPsec proposal list does not match. Double check that the IPsec proposal list matches that of
the remote side. The same method described above of using ikesnoop can be used from when the
remote side initiates the tunnel and compare it against the local proposal list. What is "extra" in
the IPsec phase is that the networks are negotiated here, so even if the IPsec proposal list seem
to match, the problem may be with mismatching networks. The local network(s) on one side
need to be the remote network on the other side and vice versa. Remember that multiple
networks will generate multiple IPsec SA's, one SA per network (or host if that option is used).
The defined network size is also important in that it must be exactly the same size on both sides,
as will be mentioned again later in the symptoms section.

There are also some settings on the IPsec tunnel's IKE tab that can be involved in a no-proposal
chosen issue. For example, PFS (for IPsec phase) or DH Group (for the IKE phase).

2. Incorrect pre-shared key

A problem with the pre-shared key on either side has caused the tunnel negotiation to fail. This is
perhaps the easiest of all the error messages to troubleshoot since it can be only one thing, and that
is incorrect pre-shared key. Double-check that the pre-shared key is of the same type (Passphrase or
Hex-key) and correctly added on both sides of the tunnel.

Another reason for why NetDefendOS detects that the pre-shared key is incorrect could be because
the wrong tunnel is triggering during tunnel negotiations. IPsec tunnels are processed from the top
to the bottom of the NetDefendOS tunnel list and are initially matched against the remote gateway.
An example is if there is a roaming tunnel that uses all-nets as its remote gateway. This tunnel will
trigger before the intended tunnel if it is placed above it in the NetDefendOS tunnel list.

For example, consider the following IPsec tunnel definitions:

Name

Local Network

Remote Network

Remote Gateway

VPN-1

lannet

office1net

office1gw

VPN-2

lannet

office2net

office2gw

L2TP

ip_wan

all-nets

VPN-3

lannet

office3net

office3gw

Since the tunnel L2TP in the above table is above the tunnel VPN-3, a match will trigger before
VPN-3 because of the all-nets remote gateway (all-nets will match any network). Since these two
tunnels use different pre-shared keys, NetDefendOS will generate an "Incorrect pre-shared key"
error message.

D-Link NetDefend DFL-260E, User Manual

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