Site to site VPN Fortigate 5.4 and Cisco- NO-PROPOSAL-CHOSEN

Xander · ‎03-27-2017

Hello,

In our company we have Fortigate 60D (v5.4.1) and I'm trying to setup the VPN with Cisco router. Cisco router is owned by other company and I do not have access to it. Phase 1 seems to work as expected ([...] - text cut for better visibility):

ike 0:phase-1-int:193473: negotiation result
ike 0:phase-1-int:193473: proposal id = 1:
ike 0:phase-1-int:193473: protocol id = ISAKMP:
ike 0:phase-1-int:193473: trans_id = KEY_IKE.
ike 0:phase-1-int:193473: encapsulation = IKE/none
ike 0:phase-1-int:193473: type=OAKLEY_ENCRYPT_ALG, val=AES_CBC, key-len=256
ike 0:phase-1-int:193473: type=OAKLEY_HASH_ALG, val=SHA2_512.
ike 0:phase-1-int:193473: type=AUTH_METHOD, val=PRESHARED_KEY.
ike 0:phase-1-int:193473: type=OAKLEY_GROUP, val=ECP384.
ike 0:phase-1-int:193473: ISAKMP SA lifetime=28800
[...]
ike 0:phase-1-int:193473: VID CISCO-UNITY [...]
ike 0:phase-1-int:193473: peer supports UNITY
[...]
ike 0:phase-1-int:193473: DPD negotiated
ike 0:phase-1-int:193473: NAT not detected
ike 0:phase-1-int:193473: PSK authentication succeeded
ike 0:phase-1-int:193473: authentication OK
ike 0:phase-1-int:193473: established IKE SA [...]

But then I get the error as follows

ike 0:phase-1-int:193473: notify msg received: NO-PROPOSAL-CHOSEN
ike 0:phase-1-int:193473:phase-2-int:4954165: IPsec SPI d888eef3 match
ike 0:phase-1-int:193473:phase-2-int:4954165: delete phase2 SPI d888eef

I've asked the Cisco admin for config details and after comparison we have

Phase_1

the same Diffie-Hellman group the same proposal (aes256 - sha512) the same keylife (in seconds) Phase_2

The same Diffie-Hellman group ("dhgrp" parameter on Fortigate and "pfs" parameter on Cisco)

The same keylife (in kilobytes)

Proposals are:

Fortigate

set proposal aes256-sha512

Cisco

set transform-set esp-aes_256_esp-sha512-hmac
crypto ipsec transform-set esp-aes_256_esp-sha512-hmac esp-aes 256 esp-sha512-hmac

Can anyone tell me what could be wrong?

I'm not network specialist and I don't know even what to ask the mentioned Cisco admin.

Any help appreciated.

Best regards

Alex

Xander · ‎08-03-2017

Hi Kadkwai

I've solved the problem after a lot of troubleshooting together with very skilled friend of mine.

I had to solve 2 issues:

1 - We had to NAT the traffic before it went into the tunnel (office lan -> NAT -> VPN tunnel)

2 - Than we received information that on the Cisco side the phase2 interface is configured to match specified IP addresses that are on the access list only (we specified the addresses before so we knew them all)

match address ac-list

My final configs are as follows Phase1

edit "vpn-p1"
 set interface "wan1"
 set keylife 28800
 set proposal aes256-sha512
 set dhgrp 20
 set mesh-selector-type subnet <- this allows to provide several addresses "remote-networks-on-ac-list", see phase2 below
 set remote-gw [1.2.3.4]
 set psksecret ENC secret
 next

Phase 2

edit "vpn-p2"
 set phase1name "vpn-p1"
 set proposal aes256-sha512
 set dhgrp 20
 set auto-negotiate enable
 set keylife-type kbs
 set src-addr-type name <- we need that to NAT our traffic
 set dst-addr-type name <- we need that to mach the IP put on cisco access list
 set keylifekbs 512000
 set src-name "our-nat-ip" <- we need that to NAT our traffic
 set dst-name "remote-networks-on-ac-list" <- we need that to mach the IP put on cisco access list
 next

src-name and dst-name you can define in

config firewall address

e.g.

edit "our-nat-ip"
 set subnet 3.4.5.6 255.255.255.255
next
edit "network-1"
 set subnet 192.168.1.0 255.255.255.0
next
edit "network-2"
 set subnet 192.168.2.0 255.255.255.0
next

and

config firewall addrgrp

e.g.

edit "remote-networks-on-ac-list"
 set member "network-1" "network-2"
 set allow-routing enable
 next

Hope this helps!

BR

Alex

View solution in original post

ajaykumark · ‎12-31-2017

Hey Xander,

Thank you so much for detailed step-by-step explanation. Had an identical scenario and your explanation saved my day !!!

Regards,

Ajay Kumar K