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Re: [FW-1] ike vpn question



Sounds like a reasonable explanation, hadn't considered it from quite that
perspective.  So can you fix it? :)

-----Original Message-----
From: Jeff LaCoursiere [mailto:[email protected]]
Sent: Wednesday, March 20, 2002 1:15 AM
To: [email protected]
Subject: Re: [FW-1] ike vpn question


I think it works like this:

Packet leaves net A which is in the encryption domain for firewall A.  Key
exchange is attempted from firewall A to firewall B (the other end of the
VPN).  Firewall B sees subnet A in the offered key, but has no entry for A
in its version of the encryption domain, so refuses the exchange.  This
could be interpreted as "no proposal chosen" in my opinion, and in fact I
have seen exactly this with my own VPN's when I forget to add the net range
to the other end...

Thanks,

Jeff LaCoursiere
Infrastructure Specialist
T-Motion


-----Original Message-----
From: Russell Washington [mailto:[email protected]]
Sent: Tuesday, March 19, 2002 7:04 PM
To: [email protected]
Subject: Re: [FW-1] ike vpn question


Ok, dug this up in RFC2408:

   Proposal: A proposal is a list, in decreasing order of preference, of
   the protection suites that a system considers acceptable to protect
   traffic under a given situation.

This translates to me as "encryption settings" on an IPSec-compliant
platform.  Shouldn't involve the source/target if "no proposal chosen" is
the specific error being reported.

-----Original Message-----
From: Russell Washington [mailto:[email protected]]
Sent: Tuesday, March 19, 2002 10:23 AM
To: [email protected]
Subject: Re: [FW-1] ike vpn question


Could well be, but my recollection is that target/destination stuff in Phase
2 negotiation is a source proxy ID/dest proxy ID issue, not a proposal
issue.  On the devices where I've seen 'no proposal chosen' and subnet
issues, they've turned up with different errors for each condition (or in
the case of a Checkpoint to PIX with a subnet issue, the PIX just didn't
answer at all).

Doesn't mean he shouldn't check the encryption domains tho.  Really curious
over here to hear what he finds.

-----Original Message-----
From: Shah, Nishith [mailto:[email protected]]
Sent: Tuesday, March 19, 2002 9:09 AM
To: [email protected]
Subject: Re: [FW-1] ike vpn question


Most likely your encryption domains (subnets defined on firewall) are not
identical on both sides.

It has to exactly match on both sides.

-----Original Message-----
From: Russell Washington [mailto:[email protected]]
Sent: Tuesday, March 19, 2002 11:23 AM
To: [email protected]
Subject: Re: [FW-1] ike vpn question


"No proposal chosen" means that the encryption settings on each end are not
in sync.  Yes, I know you said they're identical, but that's what the error
means and I believe it's defined in an RFC somewhere.  As cryptic as it
sounds, it's being as precise as it will get without saying something
verbose like "it says use DES on this side and 3DES on the other side and so
we don't agree."

Here's the rundown of settings (cross-platform) that I know will tangle this
up:

- preshared key vs RSA key vs certificates
- DES vs 3DES vs (who knows what else)
- ESP vs AH vs ESP+AH at the same time
- Perfect forward secrecy (PFS) on vs off
- Diffie-Hellman group for PFS (Group 1?  Group 2?  Group 3?)

What I've most often seen overlooked is the PFS/DH stuff.  One side has it
on, the other has it off, or the two sides are using different DH groups.

Good luck.  I haven't seen one of these yet that didn't boil down to a
mismatched setting between the two sides, and that includes the Checkpoint,
NetScreen, and Cisco platforms.

-----Original Message-----
From: Christopher Ferraro [mailto:[email protected]]
Sent: Tuesday, March 19, 2002 6:51 AM
To: [email protected]
Subject: [FW-1] ike vpn question


Gentlemen:

I have a question for you regarding a VPN a client of mine is attempting to
set up.

Both VPNs have identical hardware (nokia 650's), identical software
(checkpoint 4.1, sp4).  All encryption settings are identical.

However, when the VPN ruleset is built, an error is seen in the log on one
end of the VPN that says "IKE log: received notification from peer, no
proposal chosen."

what is the root of errors of this nature ?

I will provide more relevant information as necessary.

CF

Christopher A. Ferraro
Senior Systems Engineer
Hubbard Onemobile:www.hubbardone.com

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