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SonicWalls distribute IP addresses using the DHCP protocol. Once the VPN tunnel itself has already been established, the VPN client must perform a DHCP exchange to obtain an IP address and use this IP address for all traffic sent over the VPN tunnel. There are two reasons why this can fail:

1. The SonicWall never received your DHCP request (DHCP-Discover). That would be the case if there is an issue with the VPN tunnel itself not working properly.
   
   Try these:
   • Re-run the VPN Tracker Connection Checker from the "Tools" menu. Then try connecting the VPN again. This will let VPN Tracker automatically detect the best settings for your internet connection.
      
   • Make sure that you have no software installed that blocks VPN traffic in general. Please see this FAQ entry for more details.
      
2. The SonicWall doesn’t want to reply to your DHCP request. The DHCP protocol is designed in such a way that there can be multiple DHCP servers per network and only those who think they can fulfill a request will also respond to it, all others will stay silent (there is no “negative” response for discover requests).
   
   Try these:
   • Try rebooting the SonicWall. SonicWalls are pretty stable but we’ve seen it a couple of times that the DHCP server is acting strange, as if all IP addresses are reserved, yet that’s not what you will see in the web interface. Rebooting will fix that behavior at once.
      
   • Make sure you have sufficient addresses left in the address pool. If the pool is too small and all addresses are in use or reserved, it is expected behavior that the SonicWall doesn’t respond.