Cisco Service providers (ISPs) are interested in reducing the use of IPv4 in their internal networks because of the anticipated exhaustion of the IPv4 address space. Softwires Network Address Translation (SNAT) combines IPv4 NAT and IPv4-in-IPv6 softwires to carry IPv4 traffic through the ISP network that uses only IPv6 service. Multiple subscribers are multiplexed through a single external global IPv4 address, reducing the total number of IPv4 addresses in use by the ISP to support Internet traffic to those subscribers.