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[ScreenOS] How do I create a Route Based LAN to LAN VPN using preshared secrets to remote site with dynamically assigned IP address (ScreenOS 6.0 and later)

  [KB15075] Show Article Properties


Summary:

How do I create a Route Based LAN to LAN VPN using preshared secrets to remote site with dynamically assigned IP address in ScreenOS 6.x

Symptoms:

Environment:

  • Preshared secrets
  • Route Based VPN
  • Static IP address on one gateway
  • Dynamic IP address on one site
Solution:

This example assumes static IP address assigned at one site and a dynamic IP address assigned to the other.
The preshared secret used is netscreen.
The table shows the proposals for this example:

Site A B
Untrust IP of Firewall 1.1.1.1 (eth0/0) DHCP (local id siteb.netscreen.com)
Trust Network 10.1.1.0/24 172.16.10.0/24
Phase 1 Proposal pre-g2-3des-sha pre-g2-3des-sha
Phase 2 Proposal g2-esp-3des-sha g2-esp-3des-sha

Site A (Static):

  1. Create tunnel interface:
    Click Network > Interfaces> List
    1. In upper right corner, select pulldown 'Tunnel IF', and Click New
      1. Interface Name: tunnel.1
      2. Zone: Untrust (trust-vr)
      3. Click unnumbered
      4. Interface ethernet0/0 (trust-vr)  (or whichever interface is in the same zone (Untrust) that it can borrow an IP from)
      5. Click OK
  2. Click VPNs > AutoKey Advanced > Gateway
    1. Click New
      1. Gateway Name: Site B GW
      2. Remote Gateway: Click Dynamic IP Address, and enter Peer ID siteb.netscreen.com
      3. Click Advanced
      4. Preshared Key: netscreen
      5. Outgoing Interface: ethernet0/0 (or whichever interface goes out to the Internet)
      6. Security Level, User-Defined:  Select Custom, and select Phase 1 Proposal: pre-g2-3des-sha
      7. Mode (Initiator):  Aggressive
      8. Click Return
      9. Click OK
  3. Click VPNs > Autokey IKE
    1. Click New
      1. VPN Name: Site B VPN
      2. Remote Gateway: Click Predefined, and select Site B GW from the pulldown menu
      3. Click Advanced
      4. Security Level, User Defined: Custom, and select Phase 2 Proposal:  g2-esp-3des-sha
      5. Bind To: Tunnel Interface. Select tunnel.1
      6. Click Return
      7. Click OK  (important, unless you click OK, you will not get option to configure proxy id)
  4. Click VPNs > Autokey IKE
    1. Click Proxy ID
      1. Local IP/Netmask: 10.1.1.0 / 24
      2. Remote IP/Netmask: 172.16.10.0 /24
      3. Service: ANY
      4. Click New
  5. Click Policy > Policies
    1. Select From Trust to Untrust Zone, and click New
      1. Source Address: Click New Address, and enter 10.1.1.0/24
      2. Destination Address: Click New Address, and enter 172.16.10.0/24
      3. Service: Any
      4. Action: Permit  (Note:  Do note select Tunnel or specify Tunnel VPN because this is a route-based VPN configuration)
      5. Position at Top: Enabled
      6. Click Ok
    2. Select From Untrust to Trust Zone, and click New
      1. Source Address: Click New Address, and enter 172.16.10.0/24
      2. Destination Address: Click New Address, and enter 10.1.1.0/24
      3. Service: Any
      4. Action: Permit  (Note:  Do note select Tunnel or specify Tunnel VPN because this is a route-based VPN configuration)
      5. Position at Top: Enabled
      6. Click Ok
  6. Create static route for destination network through VPN:
    Click Network > Routing > Destination
    1. Click New
      1. Network Address / Netmask: 172.16.10.0 / 255.255.255.0
      2. Click Gateway
      3. Interface: tunnel.1
      4. Click OK

Site B (Dynamic):

  1. Create tunnel interface:
    Click Network > Interfaces> List
    1. In upper right corner, select pulldown 'Tunnel IF', and Click New
      1. Interface Name: tunnel.1
      2. Zone: Untrust (trust-vr)
      3. Click unnumbered
      4. Interface ethernet0/0 (trust-vr)  (or whichever interface is in the same zone (Untrust) that it can borrow an IP from)
      5. Click OK
  2. Click VPNs > AutoKey Advanced > Gateway
    1. Click New
      1. Gateway Name: Site A GW
      2. Remote Gateway: Click Static, and enter IP address 1.1.1.1
      3. Click Advanced
      4. Preshared Key: netscreen
      5. Local ID: siteb.netscreen.com
      6. Outgoing Interface: ethernet0/0 (or whichever interface goes out to the Internet)
      7. Security Level, User-Defined:  Select Custom, and select Phase 1 Proposal: pre-g2-3des-sha
      8. Mode (Initiator): Aggressive
      9. Click Return
      10. Click OK
  3. Click VPNs > Autokey IKE
    1. Click New
      1. VPN Name: Site A VPN
      2. Remote Gateway: Click Predefined, and select Site A GW from the pulldown menu
      3. Click Advanced
      4. Security Level, User-Defined:  Custom, and select Phase 2 Proposal: g2-esp-3des-sha
      5. Bind To: Tunnel Interface. Select tunnel.2
      6. Click Return
      7. Click OK   (Important, unless you click OK, you will not get option to configure proxy id)
  4. Click VPNs > Autokey IKE
    1. Click Proxy ID
      1. Local IP/Netmask: 172.16.10.0 / 24
      2. Remote IP/Netmask: 10.1.1.0 /24
      3. Service: ANY
      4. Click New
  5. Click Policy > Policies
    1. Select From Trust to Untrust Zone, and click New
      1. Source Address: Click New Address, and enter 172.16.10.0/24
      2. Destination Address: Click New Address, and enter 10.1.1.0/24
      3. Service: Any
      4. Action: Permit   (Note: Do note select Tunnel or specify Tunnel VPN because this is a route-based VPN configuration)
      5. Click Position at Top
      6. Click Ok
    2. Select From Untrust to Trust Zone, and click New
      1. Source Address: Click New Address, and enter 10.1.1.0/24
      2. Destination Address: Click New Address, and enter 172.16.10.0/24
      3. Service: Any
      4. Action: Permit   (Note: Do note select Tunnel or specify Tunnel VPN because this is a route-based VPN configuration)
      5. Click Position at Top
      6. Click Ok
  6. Click Network > Routing > Destination
    1. Click New
      1. Network Address / Netmask: 10.1.1.0 / 255.255.255.0
      2. Click Gateway
      3. Interface: tunnel.1
      4. Click OK

NOTE:
If the tunnel interface is bound to the trust zone (i.e. you specified the Zone Trust in step 1.1.2), no policies are needed (i.e. steps 6, 7, 8), since everything is routed. The VPN communication is effectively a trust to trust policy.


If you followed the steps above, and now you need help troubleshooting, refer the VPN Configuration & Troubleshooting Guide.
Modification History:
2018-12-27: Updated steps under VPNs > Autokey IKE.
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