How do I create a DS-Lite Softwire tunnel?

03/26/2020 3 8548

DESCRIPTION:

This article covers how to create a DS-Lite Softwire tunnel using a SonicWall firewall.

RESOLUTION:

To create a DS-Lite Softwire tunnel please perform the following:

1. Login to the firewall as an administrator.
2. Navigate to MANAGE | Network | Interfaces. Ensure that IPv4 is selected next to "View IP Version".
3. Select the drop down “Add Interface” and choose “4to6 Tunnel Interface”.
   
4. Click the General tab. Under “Tunnel Type:” select DS-Lite Softwire Tunnel.
   
   1. Zone – Interface zone. It should be WAN zone, and can not be edited.
   2. Name – Interface name. It can’t be null and the max length is 25.
   3. Bound to – The interface which tunnel is bound to. It should be a physical WAN interface. If Bound Interface is link down, the softwire will be down as well. Bound Interface can not change its zone to others.
   4. Local IPv6 address – As an interface may have various IPv6 addresses, there are two modes for the local IPv6 address choice:
      
      1. Use bound Interface’s IPv6 Address as Local Address. When bound interface is on DHCPv6 or Autonomous Mode, it would get a dynamic IP (DHCPv6 IP or Autonomous IP) as softwire local IPv6 address, and DHCP IP has a higher priority. Otherwise, if bound interface is on STATIC or other Mode, it would use primary static v6 IP as softwire local IPv6 address. If bound interface IP is released/deleted, it can be ::.
      2. Specify the Local IPv6 Address. This address must be one of bound interface's IPv6 Addresses.
   5. AFTR IPv6 address – The address will be used as Softwire’s peer’s address. There are three choices for configuring the AFTR’s address:
      
      1. Configure static Address, the address could be an IPv6 Unicast address.
      2. Configure FQDN, B4 will try to resolve it’s AAAA record. If resolve failed, the interface will be considered as “down”.
      3. Get via DHCP , the AFTR’s address/name will be discovered by DHCP.
         
         
5. Next, click the Advanced tab:
   
   1. Local IPv4 address – 192.0.0.0/29 is reserved range for softwire, and 192.0.0.2 is reserved for the B4 element. If not configured, 192.0.0.2 will be the softwire’s IPv4 address. The subnet mask is pre-configured to 255.255.255.248. The IPv4 addresses cannot overlap among different softwire interfaces.
   2. MTU – the MTU effective for IPv4 packet size before encapsulation. Softwire will automatically calculate softwire’s MTU based on the bound interface’s IPv6 MTU. When bound IPv6 interface MTU changes, the existed softwire’s MTU will be automatically updated. This is the default configuration:
      softwire_mtu = bound_if_mtu – IPv6_header_length.
   3. Like a WAN interface, there are three configuration items for fragmentation setting over a softwire interface:
      
      1. Fragment non-VPN outbound packets larger than this Interface's MTU (default enabled)
      2. Ignore Don't Fragment (DF) Bit
      3. Suppress ICMP Fragmentation Needed message generation
         The fragmentation behavior will follow [RFC2473] Section 7.2.
         
         

Configuring Route Entry

When a Softwire tunnel is configured it can be selected as the egress interface of an IPv4 route entry. We can manually add an IPv4 route entry (for example, entry 9 below) to route IPv4 traffic over a softwire interface.
Softwire is also like a general interface. When a new interface is added it will auto-add a route policy (for example, entry 5 below).

Auto Address Objects

When adding a Softwire interface, it will create two Address Objects with name “NAME IP” and “NAME Subnet”, and “NAME IP” will be added to “All Interface IP” group, “Zone Interface IP” group. “NAME Subnet” will be added to “Zone Subnets”.
When the interface is deleted the address objects will be deleted.