VPN:Configuring Site to Site VPN between two SonicWalls on same WAN subnet with same default gateway

03/26/2020 1201 12736

DESCRIPTION:

When an attempt to establish a VPN tunnel between two firewalls using the same gateway IP address and subnet fails, logs in both units may show an error indicating that the remote peer does not respond to phase 1 IKE requests or no negotiation attempts at all.This happens when the upstream gateway is not configured to handle the ARP requests properly. The issue is usually observed when both firewalls are connected through the same ISP over a DSL connection when the ISP is using RFC1483 bridging mode. Static routing is used to successfully work around this problem.

EXAMPLE: Replace the example IP addresses with those from your real working environment:

• Site A
  • Wan IP: 172.16.25.7
  • Subnet Mask: 255.255.255.0
  • Gateway: 172.16.25.1
• Site B
  • Wan IP: 172.16.25.8
  • Subnet Mask: 255.255.255.0
  • Wan Gateway: 172.16.25.1

RESOLUTION:

Site A

1. Navigate to  Manage|Network |Routing.
2. Click Add. Create the following new route policy.
   • Source: ANY
   • Destination: Create new address object
     • Name the object Site B
     • Zone: WAN
     • Type: Network
     • Network: 172.16.25.8 (site B wan IP address)
     • Subnet Mask: 255.255.255.255
     • Click OK.
   • Service: Any
   • Gateway: 172.16.25.1
   • Interface: WAN
3. Click OK.
   
   

Site B

1. Navigate to  Manage|Network |Routing.
2. Click Add. Create the following new route policy.
   • Source: ANY
   • Destination: Create new address object
     • Name the object Site A
     • Zone: WAN
     • Type: Network
     • Network: 172.16.25.7 (site A wan IP address)
     • Subnet Mask: 255.255.255.255
     • Click OK
   • Gateway: 172.16.25.1
   • Interface: WAN
3. Click OK.