Pix-vpn site-to-site

Unanswered Question
Sep 30th, 2007


I have a pix firewall with vpn configured recently. As the tunnel is not up i have enabled debug crypto isakmp and able to see the attached messages.

I have confirmed the pre-shared keys in both end and found same.

Please advice on where could be the problem. The other end firewall is not a pix which is configured with the same similar parameters.

Please help on this...

PIX Version 6.3(4)




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Overall Rating: 4.8 (4 ratings)
Jon Marshall Sun, 09/30/2007 - 23:54

Hi Rajesh

I appreciate that you have checked the keys but this message is the one seen when the keys do not match.

Could you change the key to something really simple like "test" just to make sure.


Sec IT Mon, 10/01/2007 - 01:56

Hi Jon,

I could see that the phase 1 is okay. Please find the attached show crypto isakmp sa and show crypto ipsec sa. And please suggest..



ajagadee Mon, 10/01/2007 - 06:42


If you have already checked the pre shared keys on both the pixes, can you type "isakmp identity address" on the pixes and bring up the tunnel.

I hope it helps.



Sec IT Wed, 10/03/2007 - 00:05

Hi Arul,

Thanks for your reply.

Actually i have enabled the command "isakmp identity address".

You may find the below config too..

//user configured ACL

access-list 101 permit ip remote_local_subnet user_local_subnet

access-list vpnacl permit ip host user_test_machine_ip remote_local_subnet

//ACL for vpn configured by me

access-list vpnacl permit ip remote_local_subnet host user_test_machine_ip

nat (inside) 0 access-list vpnacl

access-group 101 in interface outside

sysopt connection permit-ipsec

crypto ipsec transform-set ESP-3DES-MD5 esp-3des esp-md5-hmac

crypto map outside_map 20 ipsec-isakmp

crypto map outside_map 20 match address vpnacl

crypto map outside_map 20 set peer remote_ip

crypto map outside_map 20 set transform-set ESP-3DES-MD5

crypto map outside_map interface outside

isakmp enable outside

isakmp key key123 address remote_ip netmask

isakmp identity address

isakmp policy 20 authentication pre-share

isakmp policy 20 encryption 3des

isakmp policy 20 hash md5

isakmp policy 20 group 2

isakmp policy 20 lifetime 86400

Even i restarted my this end firewall after configuring the preshared key.

Pls let me know some tips...



Jon Marshall Wed, 10/03/2007 - 00:15

Hi Rajesh

Could you

1) turn on the following debugging

debug crypto isa

debug crypto ipsec

2) Clear any existing Phase 1 & 2 connections for this VPN.

3) Try and initiate the connection and then post the output of the debug together with firewall config (minus any sensitive info).


Sec IT Wed, 10/03/2007 - 02:18

Hi Jon,

Please find the debug crypto isakmp sa and ipsec sa.

We had restarted both the end firewalls after giving the preshared key.


Rajesh P

Jon Marshall Wed, 10/03/2007 - 02:34


Coud you post configs of both firewalls or alternatively can you check the crypto map access-lists to make sure they agree on the local and remote subnets.


Sec IT Wed, 10/03/2007 - 02:56

Hi Jon,

Shall i send you tomorrow morning @ 10am.

since i have to go to the client place and send it.



ajagadee Wed, 10/03/2007 - 06:14


Based on the debugs, the proxy identities are not matching, meaning the Crypto access-lists are not mirror images of each other.

Make sure that if you have a crypto acl on pix A:

access-list vpnacl permit ip

Then Remote Side Pix B:

access-list vpnacl permit ip



Jon Marshall Wed, 10/03/2007 - 06:17

Hi Arul

Agreed which is why i wanted to see the configs from both ends to make sure the local and remote networks match.


ajagadee Wed, 10/03/2007 - 07:07

Got it John. You Rock :-)

Lets get this VPN Rock and Rollin for Rajesh.



Sec IT Thu, 10/04/2007 - 02:11

Hi Jon/Arul,

The scenario is like this. This end we use Pix firewall where as the other end its another vendor firewall where in there is no access lists configured for vpn specifically. Remote end firewall is basically GUI based, and i could not see any ACL configuration. I knew that both the end should have mirrored ACLs. Remote end has already two VPNs up and running and they want to configure one more. In the access list option i could see only one accesslist-button-check-box which is already checked and apart from that no options... I think i need to inform customer to configure the other end by his own with VPN-ACL. But client should not say how the other two Vpns are working without ACL..Unforunately i do not have the remote end config. Please find the attached config of thie end firewall


Rajesh P

grahambartlett Thu, 10/04/2007 - 02:56


What was the spefic debug message that points to the ACL's not mirroring each other?


Jon Marshall Thu, 10/04/2007 - 03:03

Hi Graham

Basically the part about proxy identities ie.


IPSEC(validate_transform_proposal): proxy identities not supported

IPSEC(validate_proposal_request): proposal part #1,

(key eng. msg.) dest= remote_ip, src= this_ip,

dest_proxy= remote_local_subnet/ (type=4),

src_proxy= user_local_subnet/ (type=4),

protocol= ESP, transform= esp-3des esp-md5-hmac ,

lifedur= 0s and 0kb,

spi= 0x0(0), conn_id= 0, keysize= 0, flags= 0x24


For Phase 2 to complete both ends must agree on the local and remote networks they are encrypting traffic for.


Sec IT Fri, 10/05/2007 - 04:05

Hi All,

So, basically its a crypto ACL issue i hope..isn't it ?


Rajesh P

fallkaired Mon, 10/08/2007 - 00:21

Hi all,

Can someone help me please

An inside server ( need to access to a remote network

A VPN site to site is established between Pix outside ( and Multitech Firewall (

Now my inside server should connect to the remote network with this IP So I have to Nat my inside server IP ( to

The remote network should connect to inside network by the

My problem is I can establish a connexion to my inside network from the remote network but I cannot establish connexion (tcp) from my inside network to the remote network.

The weird thing is I can ping from both network each other.

This is my config below

access-list Outside_1_cryptomap extended permit ip

access-list Inside_nat_static extended permit ip host I92.168.92.6

static (Inside,Outside) Ip_172.20.20.6 access-list Inside_nat_static dns

crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac

crypto map Outside_map 1 match address Outside_1_cryptomap

crypto map Outside_map 1 set pfs

crypto map Outside_map 1 set peer

crypto map Outside_map 1 set transform-set ESP-3DES-SHA

crypto map Outside_map interface Outside

crypto isakmp enable Outside

crypto isakmp policy 10

authentication pre-share

encryption 3des

hash sha

group 2

lifetime 86400

no crypto isakmp nat-traversal

service-policy global_policy global

tunnel-group type ipsec-l2l

tunnel-group ipsec-attributes

pre-shared-key *

Thanks for answers

Sec IT Mon, 10/08/2007 - 22:28

Hi All,

vpn problem has been resolved. its an ACL issue (crypto)

Thanks for the support.


Rajesh P

Jon Marshall Mon, 10/08/2007 - 22:31

Hi Rajesh

Glad to hear you got it working and thanks for letting us know the outcome.



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