If you encounter the symmetry problem of Unicom network, it is mainly caused by symmetric NAT. In this case, it is suggested that you use virtual private network (VPN) or port mapping to solve it. Among them, VPN can bypass the restriction of symmetric NAT and realize network access by encrypting the traffic of the client and forwarding it through the VPN server. In addition, port mapping is also a way to solve symmetric NAT. You can map the ports of public IP addresses to specific ports of devices in the local area network, and use the port mapping tools developed by others to bypass the restrictions of symmetric NAT.