AR18 WAN port is of 10M*1, and the downlink is 100M*4, but it is required to connect with 100M for uplink.
AR18 is configured with NAT and DHCP, but it cannot bear them.
Solution: Configure the automatic acquisition of DHCP address to S3528G, and AR18 only functions for NAT.
AR18 uses LAN port for uplink and WAN port for downlink; it functions to perform NAT, and S3528G serves as dhcp-server.
For detailed configurations, see the attachment.